A trick that an old drag racing buddy taught me was to add an equal diameter tube onto that flange. say, 22 inches long. Paint it a light color with hi temp barbeque paint. After a few runs, cut the tube where the paint stopped burning up. It is now ideal length,
its good for finding where to put h pipe or x pipe too. but go in a little before the paint stopped burning as the pipe picks up some of the heat too and its not the exhaust gas burning it. a line in crayon or china marker works too.
Very good video. You are 100% correct about the scavenging effect and the power pulses. (Same goes for the intake, look at Chryslers ram induction). Our rule of thumb was to install a collector that was painted, run the engine at about 2500 rpm and see where the paint burned off on the collector. Then we would cut the collector at 3" past the paint burn off area. This was back in the '70's when we were doing this.
He's only saying half the story,! There are positive and negative pulses. One helps pull charge in during valve overlap and ex gas out. It also reflects, positive pulse to prevent charge being wasted out of exhaust. Shorter the pipe, sooner it occurs....ie high rpm I'm going to leave the chat now, can't teach old dogs etc, just do some reading.
Sorry mate. Same for my other comments, the things you describe must be quirks of such engines ....long header Vs shitty cast ex is obviously better( mostly) but it's not because they're longer it's cos they just flow better etc. Please research exhaust theory......I was going to say nowt else but it's so irritating...... you make your engine faster etc no doubt but you just guess why! Sorry.
@@peterjohn3180 i know there are math involve and the length for the pulses. there is a spoon civic that the runner itself cost more than the car itself. its so long that the entire engine bay need to be refitted to include the engine relocated so the exhaust runner could fit in. ruclips.net/video/j9p24qIjWSQ/видео.html
I tried to make it easier to understand for the "New Guy" hence the channel name 😆 ruclips.net/video/1CzGFoXwrfo/видео.html Did one for if you are running forced induction!
As a 65 year-old hotrodder, you explained this well and correctly. However, I never uncorked headers to gain power. I only have raising hell and making noise on my mind. Is that bad?
Only if you do it at 3:00 am after s night if drinking and then do a burnout in of a friends driveway. Not a good way to score points with the friends parents. 🤷♂️
@@danmyers9372 I like your style! At 65 I still raise hell but none of the parents are still alive. Come to think of it, almost all of the real hotrodders in this area aren’t either. But your idea is solid!
You are 100% correct. Back around 1974 I took my street driven 1970 Mach 1 to a test n tune. I uncapped my street headers and fought with the car all day. It definitely lost torque and was running a good 2-3 tenths slower than what it ran on the street. Being an ignorant kid I tried rejetting the carb, switching carbs and changing the timing all to no avail. It was a turd, especially down low. If only I had had some bolt on collector extensions!
You are mostly correct but there is one part you're missing, scavenging occurs because of a pulse that is sent backwards whenever the exhaust pulse reaches the collector, think of it as a ripple in a pond bouncing back after hitting a dam. Basically you are trying to catch the vacuum on the bounce back, which pulls the air into the cylinder over exhaust and intake overlap, thus creating scavenging. This only happens over a short rpm band, and this rpm band is determined by the distance from the valve to to the collector, and the longer the header the higher up in the rpms you catch the scavenging effect. Now because it works like a wave there will probably be 4 or 5 peaks in torque that you will see in decreasing magnitude, but if you aren't running high enough rpm it is absolutely possible to have too long of headers and so you won't be catching the first and strongest pulse, instead youll be using the second, much weaker pulse. Anyway I hope this helps someone learn something.
Maybe people should give this a listen, each tube needs to be a specific length and diameter for a given cylinder, and horsepower/rpm range: ruclips.net/video/f72BMpmoGMY/видео.html
Dang, world of knowledge going on here, this is very interesting. Sounds very similar to the concept of 1st, 3rd, and 5th harmonics of a fundamental frequency where the 1st harmonic is larger in amplitude than the 3rd and 5th.
I can confirm this information is 100% true. My engine on my 73 ford makes more torque with mufflers but lacks the top end power of open headers. When I tried just running open headers I had great top end power but horrible bottom end torque. When I ran 18 inch collector extensions on my headers I got the best of both worlds. With the extensions I seemed to have way more torque than I did with the mufflers and just as much top end power as open headers and a better throttle response. My car is definitely faster with the collector extensions!😁
That's why I made longer collectors to my headers, tapering the pipe down to my exhaust pipes. Great breakdown and explanation of scavenging the exhaust pulses.
This is very well explained. Another thing here, when the exhaust (gas) scavenging is less efficient, so is the heat scavenging from the head (Referred to as waste heat, QC, in determining thermal efficiency of a heat source, n(efficiency)=W/Qn, or, (W/Qn)=((Qn-Qc)/Qn), or said, Work in Joules over Resevoir Heat (in) (Engine) (Joules) equals Resevoir Heat (in)(Engine)(Joules) minus Resevoir Cold (Header outlet)(Joules) over Resevoir Heat (in)(Engine)(Joules). Increasing exhaust efficiency with the longer header add on also increases heat transfer efficiency and therefore contributes to added power/torque. By increasing thermal efficiency, we can increase the Work (W) produced, and if we produce more Work in Watts...then we create more HP. 746Watts is approximately 1 horsepower.
Excellent description. I've seen older bikers tuning their bikes with a sliding exhaust listening to the tone change. Take an exhaust off a two stroke it virtually stops.
Two strokes need back pressure and scavenging otherwise they're a mess I used to have a Suzuki 250 Hustler X6 1970 it was a fun little bike I'm surprised I lived through it have a great day
When a fella has an engine on a stand in his living room, listen to everything he says about engine building. That’s hardcore. A guy who knows his shit
It is all about your engine. There is a racing procedure to get the optimum collector pipe length. I actually read the real hand written instructions by Grumpy Jenkins.
Scavenging effect goes all the way up to the next intake charge (camshaft overlap). Also, you can use white fingernail polish to draw a line on the collector extension. Make a few full throttle passes and cut where the white turns brown.
@@newguysgarage6802 Yes, I watched it. I simply added that those exhaust pulses also create a vacuum to pull the next intake charge into the cylinder. That's why camshafts are ground with "overlap" so that the exhaust valve and intake valve are open at the same time. The amount of overlap needed is dictated by the intended use. At the collector, pulses are merged from other cylinders to increase the "usefulness" of these pulses. However, as exhaust gas cools it slows down and becomes a restriction. Optimally we want to keep the fast/hot exhaust gasses and expell them quickly when they slow down. This is done by tuning the collector length. You can guess at optimal collector length or you can get a pretty good idea of optimal length my checking temps on the collector. Measuring temp on a long bare metal collector with FLIR would probably be the best method currently available. However, you can get close with white fingernail polish (the cheap stuff...not extended wear or anything) or you can use temp paint. It's not going to be a sharp line. Remember, even if you apply it on a dyno, we're seeing the result spanning across an RPM range. It'll be a gradient. So start at the beginning of the gradient and fine tune from there.
Yep i have other videos explaining overlap too lol. But my point was with the paint stripe actually not working to find optimal collector length. With the paint trick you will almost always cut it too short because exhaust dose not have to be hot enough to burn paint to still be hot enough to flow. Only time paint trick is close is when using large primary tube diameters, because they naturally want a shorter collector length so the paint is closer to optimal simply by coincidence 🤔
You should check out the old school Mickey Thompson Super Scavenger headers with the long racing style collectors and mounting flanges for street exhaust systems. The best of both worlds.
Back in the day I put a big block in my 68 Camaro and I had to run header mufflers for a couple weeks until I could save up the money to get the exhaust system done. I swear the car had twice as much bottom end torque after I got the full exhaust system installed. Back then you had to bring it to a muffler shop and have the system custom bent. I ran two and a half inch pipe with a set of Turbo mufflers. I miss that car so much, I should have never sold it!
Still have my 69 Camaro convertible I bought in late 1983. Been bringing it back to life the last couple years. Grandson and I rebuilt the engine last year. We also put in a new transmission , disc brake conversion, new suspension front to back and a new moser 12 bolt posi. Starting to shape up nicely. Been off the road for several years. Understand about missing it. Glad I never sold it.
That was a lesson I learned in my late teens when I bought mine. ALL of the older guys back then all said that same thing. They all wished they still had their “???” car from when they were younger. I learned from the older generation and said I was not going to be that guy. Now I get to pass it on to my kids/grandkids.
That's why when I built my own 3 inch exhast system for my 340 Dart it picked up a very large amount of power. The combination of 3" header collectors and 3" exhaust pipes to the mufflers extended the scavenging effect. Mandrel bends and good mufflers lowered back pressure to increase the flow in the exhaust system at all rpms. My previous exhaust system when really examined at its bends was pretty bad.
My friend had a 1972 Dodge demon we had a lot of fun with that Mickey Thompson 14s up front and 15s L60 15s in the rear with Craig SS all the way around man that was a fun car we had a lot of good times took it to connecting highway if you're from the East Coast you'll know where that's at have a good day
I agree, I ran long tubes and 3' exhaust on my FE 390 and it really woke up compared to what previous owner had them dumping into 2" all the way back. The old Indy cars ran extra long headers, essentially a very long collector. But I also think cam duration has a lot to do with how the exhaust is tuned after the initial dump into a street length collector. The old school high lift cams were not as technical with full duration as engines of today. So I can see why they got the good results they were after by simply measuring where mass heat ended vs newer engines need the math formula. Of coarse we know math formulas can be reliable to get us close but still advisable to play around with different set-ups behind the collector. The small exhaust ports gripe my ass on the Vortec V6 heads. I wish someone would make some 202 style heads for that little engine that could. I hate depending on boost for power. Freaking vacuum cleaner sounding POS that won't last 100,000 miles if you drive them hard. Just my opinion.
Great video! You should make another header video that describes the physics how exhaust manufacturers & many authors concluded short collectors are favored for horsepower and longer for torque. Smokey Yunick mentioned in his book Power Secrets how tricky in his attempts with exhaust, He actually figured out ways to find natural low atmospheric pressures under the chassis of moving race cars and "dump" header pipes there. He was genius in many "waste not want not" hp gains.
Its alwase better to be to long than to short with collectors. The power lose from being to long is verry minimal but the power lose from being to short can kill all of your bottom end. Not to many cases were you would give up 50 foot pounds below tourqe peak to gain 10 hp at the top 😅
Currently collecting the parts to build a rat rod, I appreciate that you not only identified the problem but also offered the solution, that info will be put to use on the build, thank you 🤙🏻
Back in the day I ran my 69 Road Runner with full exhaust but where the headers met the collectors instead of a gasket I put a washer in between the bolts for a little gap. That seemed to work fine. A lot of Mopars in the Washington DC area back then ran like that.
Weird idea, but I think i can see how it works. Velocity of exhaust pulse jumps straight past the breather gap, and if the vacuum behind the pulse is too great it draws air from outside to keep the velocity up in the pipes I take it. Now if I'm right about that, that's bloody clever and I love the idea! However I'm no exhaust expert, I'm just trying to make sense of it with my limited knowledge of physics
@@YouNameItGaming how does introducing outside air into the system that goes back against the flow increase velocity? Further more at that point you lose the draw of the hot exhaust pulling the burned gasses out of the cylinders and the valve overlap ..when both vales are open at the same time drawing fuel and air loses some of its effect ..well actually what happens is the lower pressure that is created internally or vacuum from escaping exhaust leaves a void that the atmospheric pressure above the air intake tries to equalize it forces its way in and if you have x about of space that has air moving thru it and then the space is reduced the air behind continues to push meaning in order for the air volume to vmcontinue it has to speed up ..the velocity effect ...
@@jamesgibson5876 "how does introducing outside air into the system that goes back against the flow increase velocity?" It doesn't. Nobody said anything about increasing the velocity! Like I said, I'm not an expert in exhaust, I'm just trying to make sense of how it would work if indeed it does, and the way I speculate that it would work is if the exhaust pulse carries momentum down the exhaust tube and follows a similar principle to a bullet in an insanely long barrel (expansion completes whilst bullet is still in barrel, the momentum of the bullet creates a partial vacuum behind it, bullet loses velocity) and so allowing air to enter behind it in such an event would in theory reduce the the partial vacuum behind the pulse and reduce the potential for lost velocity. Now to be fair it could lead to a reduction in scavenging, but I simply do not know Now once again, I'm no expert and I could be and probably are wrong, but you're clearly not looking at it the same way I am
As long as those headers seem I’d guess they are for around 4500-5000rpm at that diameter, often will try to incorporate two pulse per runner before the collector for higher rpms in some theories but using theory and formulas only goes so far, as nothing beats making it and testing it, the best I’ve seen is 8-1 system with an adjustable length collector it makes an ol gm v8 sound like a formula 1 engine
Yeah I saw a mini modified puller tractor back in the mid '80s with an 8 into 1 that screamed but seemed to do better than the 2x 4 into 1 tractors with the same capacity SBC
Most of the tuning I've done internally on my engines is cheap free horsepower take your pistons and balance them take your sharp edges in your motor & chamfer allow for good air flow allow for good oil flow run high Volume oil pump but the price of the pump is worth it saves you from losing a motor and the main thing port and polish you're intake it's simple get your sanding rolls and a long extension polish it out match it to your heads with dicem blue and you'll get free horsepower also make shore your rotating assembly is well balanced and it's real simple have a good day
Port.....but not polish lol If you get the intake verry smooth then that lets the fuel come out of suspension and puddle up along the port walls. On a carburated engine anyway.
@@newguysgarage6802 yeah it’s a complicated topic and it’s different for different parts of the port, and can be counter productive in the wrong place causing more fuel to come out of suspension than a completely polished port Eric weingartener has excellent porting videos and has done some testing with golf ball ports from memory should not be done on the port short side
Thanks for this video. This gives me ammo in my arsenal to send my buds who are just not educated on the science dynamics behind what exhaust actually does to performance.
Hey Buddy, in the 70s,I use to make, what us Kiwis called, freeflows,for various models of cars. Every pipe has to be the same length, no matter what room you have under the bonnet. When finished, I tested them by blowing air down each pipe, and holding a cigarette paper over each other hole, to make sure that they all sucked the paper out. Works everytime .Loved your presentation.
You are partially right ! The fuel/air mixture enters thru the intake valves scavanges the burned gasses, passes thru the exhaust valve and cools the exhaust valve on the way out. Valve overlap duration, header diameter and length, intake diameter and length needs to be all in tune. A portion of that fuel/air mix that is now partially in the exhaust reverses direction by the pulse of the next cylinder exhaust. That pushes back thru the exhaust valve and back into the cylinder along with the incoming fuel/air from the intake and will increase the cylinder volumetric efficiency. An open header will reduce the double charge efficiency of all the cylinder. Some back pressure is necessary to improve torque and hp.
I want a cold intake. Please use water to cool the stem and seat of the exhaust valve. Scavenging is to suck out the heat early and to suck on the piston surface while it moves up.
@@newguysgarage6802 Dragsters and funny cars have short, stubby individual pipes because they REALLY make power. Same for airplanes in WWII if they didn't turbos. *The KEY is matching the flow rates of the intake **_with the exhaust_** AT the most operated RPM.* Think about this - how often is a street driven hot rod operated at wide open throttle? Not too much, most of it is at cruising speed with some hard acceleration now and then. How often is a legit race car driven at half throttle? Almost never if it's a top fueler. For a V8 street car the _best_ option is not a '4-into-1' but a tuned crossover OR 'tri-Y' header with a dual plane intake because it has the best wide range of RPM flow characteristics ... unless you're literally drag racing from stop light to stop light but that's going to get you arrested.
.......you are misunderstanding why dragsters use zoomies. They are supercharged and running a high volume fuel. On supercharged engines air is getting forced into the combustion chamber and during overlap pushing the exhaust out. The reason scavenging makes power is because it is helping pull the intake charge into the cylinder during overlap. On a supercharged application that is not necessary and as such exhaust scavenging is less important. At a dragsters level were they are also running a high volume fuel along with that all they need is to get as much out as possible AKA zoomies. Now radial engines, they do not use headers as we in the car world would recognize because of packaging restraints in the airplane itself. They make about 1,200hp which seems like a lot until you realize they are 1,800 cubic inches..... thats like a 302 making 250hp....stock manifold territory....
In 76 I built a 390 4 barrel for a friend with a 66 mustang fastback and stuffed it in with headers for the exhaust i had a muffler shop where a friend of mine worked make up a custom dump gate aimed down and out you could either run standard duel exhaust or uncap the turn outs so he could make a LOT of noise .his neighbors hated that car but at night the fire coming out of those pipes and hitting the pavement at the local car hang out was something to see . O to be 18 again .
You can also add a High Flow Catalytic Convertor at the flange on the headers, they give the hot gases somewhere to expand in to in a similar way to the expansion volume on properly Tuned Headers, without restricting gas flow, and clean up the cancer causing gases in the exhaust.
I did this on my GTO and unfortunately that theory doesn't hold true. The car was completely gutless on the bottom without the catback. The converters are about 20-24 inches in length past the collector. Kooks 1 7/8 headers with Hi Flo cats. Put a 3 inch stainless works exhaust on with x pipe and it runs awesome.
@@prowler10393 'GTO,.. brain went 'what model GTO from the '60's/70's had cats,.... then went 'Ohhh, Commodores,...' Yeah, removing the Cats from the DunnyDoor is a bad idea, back to those Aromatic Organic molecules in the exhaust making people sick who breath them. As for performance, 'gutless without the catback',.. So it had power with the cats in place? High Flow cats have that funnel shape at both ends to expose the whole front face of the honeycomb to the incoming hot gases, which transfer a lot of heat in to the honeycomb, by the time the gases leave the cat they can fit down a pipe easier as they have been cooled by that heat transfer.
A guy giving me advice and insight on header and scavenging technology.......on a header.....on a motor.....on an engine stand in his kitchen. Thats pretty much a ''must subscribe'' in any gearheads book. In subbed.
That was actually one of the better explanations I´ve heard on the issue. Nice, very nice. If I may I would like to add something that might help. The pressure wave that is provoked by the escaping gas out of the exhaust port is just that, it´s a wave. Meaning there are peaks and valleys. Simple so far. If you have an open exhaust those peaks and valleys help scavenging but only a little bit, i.e. you do not generate as much power as you could be. By extending the collector and/or reducing the actual exhaust tip you provide a reflection point for that wave. This new wave has more restriction for the gas flow so the AVERAGE pressure of this wave is actually higher than an open header. But, BUT, this new wave has higher peaks and valleys. The valleys are actually a slight vacuum and as the new wave has a LOWER valley it´s pressure is actually lower than the valley of the open header. It is this lower pressure (valley) of the restricted wave that provides more of a pressure differential during valve overlap. This higher differential forces out more of the remaining spent gases and that leaves more room for a fresh charge of air/fuel mixture. In other words, if you want more power you need more air/fuel in the cylinder BUT before that can happen you must first evacuate the spent air/fuel from the last power cycle. Provoking a higher amplitude wave by restricting it a bit gives you higher peaks and valleys and that equates to more room in the cylinder, i.e. more power. So if you say you need back-pressure you are correct and wrong at the same time. There is no one, single pressure in an exhaust system at any one time. Rather, they are full of waves (peaks and valleys) and it just so happens that the wave with the HIGHER AVERAGE PRESSURE provides the LOWEST pressure. Hopefully that makes sense.
hi, i used to race on the Atacama desert with my nice patrol v8 and i always used long headers (not that long as in the video, because they didnt fit), but i did run a tube between both sides, joining left and right after the collector and the torque gain was huge. I think the old nascar cars made this too :) (im not an expert, but read that in an old hot rodders forum). That compensate both sides of the engine and it was very smooth, considering the cams i did use. Im kinda old school. :). it was a 2 main bolts 350, bored to 355 with 10.5 compresion, arp bolts, alu intake, rods, flat pistons , crower cam, lifters and a small edelbrock carb ( i thing it was between 500 and 600 or something like that) with an offroad kit (this kit was awesome). Very nice video explaining the scavenging effect. At the end it comes down to where do you need torque/hp in the powerband. I could bash 40 degrees dunes without having fuel issues and i didnt died, so i think it was a good combo :D.
Yep! Connecting both sides of the engine together is essentially a second collector allowing pulses from one side to help pull out the pulses from the other 😁
Er..... 5 inches over bore? I've never heard of such a thing on a small block ...hell you could get five inches with a hone...as for 500 or 600 ..what ? Horsepower? On a naturally aspirated engine your going to work very hard to do slightly better than one horse per inch and it won't be cheap. So 500 or 600 seems sorta uikley ..
@@jamesgibson5876 Hi, CFM, these numbers comes after Carb... :), the engine was .030 overbored. The engine was used and not in the best condition initially and the pistons where a gift from a friend :D. That was in Chile, where we cannot buy easy a v8. It was very difficult to get that motor. hp... well, 5 here, 5 there, at the end i wanted reliability and 320+ hp, from an engine that was originally 210 hp and the most important thing, it cannot die in the middle of the dessert with hi temps. Found an old video :D. Carb and suspension wasnt set yet. ruclips.net/video/5Fyns2gXMl0/видео.html found other video :) ruclips.net/video/0Jr8GKtPXoQ/видео.html
I used to run a 383 stroker motor dome Pistons basically a 350 with a 400 crank man great little motor get a lot of horsepower for the whole deal with basically stock parts you modifications but it was worth it I'm 69 years old & old school I worked in a machine but did most of my modification in my garage with simple hand tools have a good day
@@jamesgibson5876 I think he was saying .005 or .006 so before we used to run our bores a little bit loose not quite that loose we went more like three or four just to get the motor to run good without too much resistance on the cylinders have a good day
62 year old son of a former drag racer. I never ran open headers. I had a buddy of my Dad weld up a collector with a wedge to help scavenge an bolted a high flow glass pack to my 428 Cougar. Never noticed even a tenth at the track.
All engine combinations are different. My old supercharged sbc hated exhaust of any kind and didn't care about any length of extension on the headers. But I also know guys who pick up a tenth or so with extensions. Experiment to see what your motor likes.
I have a boss 302 engine in my 68 F 100. Makes plenty of torque with 5 inch diameter collectors made from a dodge drive line. Like you said. Every engine is different.
@@jesse75 Lol to let you know how crazy overkill that probably is the downpipe on my 600hp turbo Coyote is one 5in pipe and it's probably still overkill. But whatever turns your crank.
Good video. A heart murmur is similar and for similar reasons. If the flow becomes turbulent at the heart valve (exhausting), the result is poor flow. Poor flow robs efficiency and creates a loss of power and a suffering of output. Engines from air induction (air cleaner/filter housing/or air horn/hat etc) to the end of the exhaust pipe and everything in between needs to be built around each and the total. Not doing so is a crap shoot and ends up being mostly chance that you are not leaving power on the garage floor/workbench. It's a fine line between the art and science. It takes science, and the true artist, knows how to use the science to the fullest. Those are the folks that win consistently over time.
They used a cutout, which came close, but, they didn't test a 12 to 18 inch extention designed for scavenging...true extensions would have made the most torque...
They did an entire episode on extensions, ,conclusion, at least 18 inch stub. After 24 inches ,no significant gain on hp/torque, or backpressure increase. Need to rewatch. I do know this my 427 AFR Headed SB stroker, 60 fts a little quicker with stubs, as opposed to open headers. as well as a slightly better ET.
Thank you for this and it reassures that what they did at the garage where I got my open headers on my Chrysler 5th Avenue was the best set up! It's a very lean burning car with very little horsepower, but it just sounds amazing on the open road!
I agree with the comments below that say it depends on the setup, and also that long tube headers don't always make more power, thats why high rpm engines use short pipes and no collector. Long tubes are usually for low end torque... And I would also like to say that some engines do need back pressure if that is how they were tuned from the factory. Many engines will run too rich or too lean if you just change the exhaust and get rid of the back pressure. Just ask the people who've burned holes in their pistons shortly after getting rid of their back pressure.
.......change the jets in the carburetor then!? Running too rich or too lean is not a flow issue its a tuning issue! That is the worst excuse ive heard 😆 🤣 😂 Your talking about zoomies on NHRA drag cars they are supercharged. Supercharged engines do not rely on scavenging and vaccum to get exhust out and help pull fresh intake air into the cylinder on overlap. Long tube headers are for high rpm not low. Shortie headers and cast manifolds are for low end around town everyday driving, thats why they are short from the manufacturer.
@@newguysgarage6802 If you say so, I'm just really glad you're not tuning my motors. My 468 BBC at 8500 rpm told me it like shorties, and as a bonus we get to make snow cones with the frost from the tunnel ram.
@@newguysgarage6802 Then I guess you're running straight out of the block if that's your mentality we don't need any back pressure we don't need any collecting we don't need any stinking badges
I read an article about exhaust systems and it stated that a simple one pipe exhaust with no muffler would make more power but the length of the pipe would make it unfeasible for a vehicle as it would not be able to fit. Now this is for a stock application and the article was in a Popular Science or Popular Mechanics magazine back in the seventies.
Excellent video and explanation! I do agree this to my surprise is still filled with misconceptions and your video explains a lot real well :) length = helps scavenge I did a drawing w/ animation pertaining to Volumetric efficiency and stated that as soon as the exhaust column exits the tip of the exhaust? The length itself “pulls” the newer oncoming exhaust from the head hence helping “scavenge” Your words are perfect “you’re not taking advantage of what the header is capable of” Thank you for this love it!
And I do agree with Mr Meyer on the comments on the intake it’s the same but inverse or the opposite… prolly why “stacking” was used in the term “velocity stack”
Honestly have not done any kind of tuning on gas engines, and never heard of scavenging from exhaust, but I understand and it makes sense now. Nice vid.
Excellent video, I put header insert mufflers in my 3.5 collectors and got an extra 4 inches of length on a 3 inch system netting 18" before the bend and boosted low torque.
I've been building winning race engines for over 30 years...and everything this man is saying about collector length is 100% correct. We dyno tested different collector lengths and found that just 1" can make a big difference. Great video brother!
Tomorrow my Cutlass is finally going to the shop to get longtube headers installed, thanks for all the help and for checking out my video to see if they’d fit. You are awesome! ✌️
Contrary. I actually lost power running an exhaust over open headers. Fair. That being said, I run a supercharged motor. And Scavenging on a N/A motor is so much more important it can be considered second-nature at this point, to the end of Scavenging and Backpressure being used interchangeably, as in order to get scavenging, you need channeled/directed flow through a restrict or that creates fluid adhesion to create a vacuum. Additional. “Backpressure” in the 4-stroke world doesn’t mean the same thing as “Backpressure” in the 2-Stroke world, as 2-strokes need specialized exhausts that create actual restriction to create enough vacuum for scavenging to take place. Backpressure (referred to correctly), in both applications is just a way of directing and funneling flow to create a scavenging effect. I could go on all day about Camshafts and Lobe Separation/Overlap, but I’ll leave that for everyone to research into and make their own conclusions on. It’s real simple, the information is out there and it’s the sorta information that wins races when the finish line is determined by 1/10th of a second of acceleration, and it’s decades-old knowledge as well. Conclusive. The confusion comes from a mix of fundamental misunderstanding of fluid dynamics, a fundamental misunderstanding of 2-stroke motor operating principles conflated with 4-stroke motor operating principles, ego (on both sides to some degree), and the absolute fuckup that is the English Language.
I didn't really understand the wording but I understood that the manifold actually works collectively with the engine to pull the exhaust out. So I knew long tubes with longer straights after them worked better than short tubes or street long tubes with no extension. Couldn't explain it well to my friends so this video is going to them for the science!
The tube length is a frequency thing. The length can determine if you get a 2nd order harmonic, 3rd order, etc... (imagine stretching out a slinky between your hands, then twitching one side. You'll see a tight spot go back and forth until it runs out of energy and fizzles out. Same thing) The reason you need is collector extension, is because the collector can't do it's job, if an inch or so later, it dumps to atmospheric pressure. When that happens you no longer have a low pressure area at the other 3 tubes. When you have around 18" after the collector, that gives you about a foot of area to have a 'stretched spring' of air in there. And that 'stretched spring' is there pulling on the primary tubes.
Well described and beneficial for noobs but I have to partially disagree. You have two sonic waves occurring, one at the end of the long pipe where the wave bounces back to the valve, and then returns, and a second sonic wave bouncing back form the rear of the collectors next opening. That's why the collector (or expansion chamber) also benefits from being tuned length to the pipe diameter/volume, speed of sound and the required Nominal RPM. Obviously the length (tuned RPM) of stock long pipes cant be changed so you need to match the collector either to a short dump (Large longer pipe), or a long tuned exhaust at the end of the next stage usually at a muffler using the short adapter (in this case the second sound wave bounces off the tuned location of a muffler. The pipe size is also important as you need to time how much exhaust gas can be drawn through the pipe before the next sonic wave and vacuum cycle.. A full tuned exhaust will have multiple sound renascence points. A muffler will also act as an expansion chamber or resonance point. It's all about the sound length and total volume of each stage which is matched to the desired RPM. You can have 1 x resonance length, 2 x resonance length and so on. Long resonance length usually smaller diameter pipe, larger diameter pipe = shorter resonance length, but its all a balancing act. > It's complex stuff to work out but Phil Irvin(Engineer) describes all the formulas quite well. I think it was in "Tuning for speed".
I showed this video to my wife. She thought I was the only one that kept a hot rod motor in the living room. Had a S.b. 2.2 in front of my T. V. Till the rest of the ride was ready.😅.
I went through this with my wife's Mach 1 Mustang and Flowmasters vs Magnaflow and I can tell you there was a seat feel difference. The Flowmasters had more seat feel than the Magnaflow. We think it was from the back pressure from the baffles in Flowmasters. 🤔
That feeling that you were getting. Are you sure it wasn't that drone that Flowmasters are known for? Especially in a Mustang where they placed the muffler. Depending on the year I've seen many in the middle of the exhaust pipe. Normally we would expect to see them at the end. Not in the Mustangs that I've worked on back in 2002, 2003.
I owned an exhaust shop in Tn. For 17 years. You are exactly right. I use to tell people to run atleast a 12 inch extension off the collector. On our drag car we also scavenged off the valve cover to the backside of the collector.
1:14 No vacuum is created, just moving exhaust gases create a low pressure which helps the next pulse of exhaust to come in behind it. If it were a vacuum then the exhaust wouldn’t move down at all. It’s not correct to say the standard car exhaust manifold doesn’t scavenge, of course it does, it just can’t do it as good as extractors or high performance pipes will, is because the car manufacturer has to compromise between fuel economy, usable power at large rev ranges etc, a race setup has to forgo fuel economy naturally to achieve high hp, which is why these pipes will suit this style of driving. But you can’t have it both ways. A daily driver will have back pressure simply because of these compromises and the manufacturer has designed it for peak performance and economy for those conditions. Yes those pipes can be way shorter, top fuel dragsters have foot long pipes at most pointing upwards, whatever gets the result for that particular engine, the longer pipes aren’t better or worse, just depends on when you want that power range to be.
I read this in a book 50 years ago and the book was 30 years old at the time. The English had it all figured out and there was a magical number for the length of the pipes and for the life of me I can't remember. It was either 36 or 38 inches long for the open headers to give optimum power. Y'all probably know it though.
It changes with every engine. You have to take the total flow of the exhaust port and match total exhaust volume to it for optimal tube filling........................but for us that dont have the means to do that "18 is a good average for collector extension length. Its always better to be to long then to short. The power lose from to long is way way less that the power lose from to short.
Nonetheless there were still people that run any exhaust that makes their engine louder that's their reasoning the louder the better that's all they're concerned about not talking about everybody but there are many out there that believe this
@@newguysgarage6802 I got ya". I live in Canada and had my motorcycle in my place all winter a few years back. Why leave my baby outside? That lowers the resale value.
Yes you're 100% right my son and I used to race a Z28 1976 circle track that made a difference that little piece of pipe have a great day thank you very much
Just seeing that manifold is reminding me of an argument I had a with a guy about the difference between a manifold and a header. The guy didn’t know the difference and was trying to argue that it related more to how much power it made than the design of the part. Power is a byproduct of the design.
I have seen this happen on some cars, but Different combinations are different. Most guys uncork at the dragstrip because they have timeslips to prove it works, they may loose torque especially without an extension pipe, but most make up the difference in the top end of the 1/4 mile We ran a 440 six pack, HUGE cam, Open headers were worth a full second over high flow manifolds with cutouts. Removing the exhaust and running open headers no extension pipe, 3 tenths quicker than corked up with 2.5 inch glass packs. All my mopars had similar results, 383s, 440s and a 400. Even with 3" exhaust. Extension pipes would certainly have helped. But weren't easy to install around the torsion bars. In my many years of drag racing, none of my cars, my dads cars or my friends cars went quicker with exhaust on, and I ran straight thru mufflers dumping ahead of the axle. I now have 3.5 inch exhaust with 4" mufflers. Dropping the exhaust out just saves weight, but doesn't slow the car. But I would gain from tuned extensions. Alot of torque loss actually can come from leaning out the engine sans mufflers. We dialed in the timing and carb on open headers. Definitely ran rich on mufflers. I can prove on a dyno and at the pull track or dragstrips that tuned extension pipes work. Also, we went from dented, beat up $75 1-3/4 blackjack headers to $600 tuned length 2"primary tubes, 3.5 collectors and went 4 mph faster but 2 tenths slower! Lost all that torque in the first 60 feet. Should have had a 3" extension pipe.
If you think of each pulse as bingo ball bouncing off of each other in the short header and creating 'turbulence' verses each pulse escaping the pulse zone individually on the long tube. The part about creating a vacuum totally drove the image home for me as well.
Thanks for the reply, I am rebuilding my 460 motor payed for my new headers. So it’s going to have the power,it being a 460 and all well see ya next time see ya bye.
Next you should teach everyone how to get the optimal collector pipe length for power & torque. When I was in high school I read the hand written notes on how to do the procedure from Grumpy Jenkins. All engines are different and have different lengths.New sub. I’m old school and been a mechanic for 40 years and work on big trucks for a living.
The only true way is just trial and error lol Start long and chop a little off until you run your best ET The old paint trick dosnt work...so that is basically the best way of doing it is just by going out there and making runs 😅
This makes sence I have longtube headers on my 87 4Runner and they always come with that collector extension I figured it was just so you can bolt and unbolt the rest of your exhaust more easily it’s nice to know it actually helps scavenge the exhaust the headers alone with a 22re you can definitely feel every hp gain
That one I had is just for coupling the rest of the exhaust together 😅 You would want one that is 18" long (that seems to be the best average length) and have it the same diameter as your collector 🙂
While I knew everything that you explained, I really appreciate the simplicity of your explanation. An engine is an air pump. More in, more out, more power.
Open headers make more noise, noise=power. Lol Right out of high school I worked in a shop with chassis dynos. It became apparent that noise DOESN'T equal horsepower pretty fast. Great video!
A similar problem happens with motorcycle exhaust. It's called reversion. When you're running an open exhaust, we put a "lollipop" in the end. It stops the reversion, and you still get the flow and the power. Also, your house looks like the inside of my house. Instead of an engine on a stand, there are motorcycles.
While Engine Masters has taught us: *Theres a 1 to 2 hp difference between long and mid length headers. *Header extenders gain 3 to 4 hp more. *Theres a 1 to 2 hp difference between X and H pipes.
A trick that an old drag racing buddy taught me was to add an equal diameter tube onto that flange. say, 22 inches long. Paint it a light color with hi temp barbeque paint. After a few runs, cut the tube where the paint stopped burning up. It is now ideal length,
The paint trick is a bit dubious at best lol 😆
But will definitely get you in the ball park 👍
I have heard of that old trick!
its good for finding where to put h pipe or x pipe too. but go in a little before the paint stopped burning as the pipe picks up some of the heat too and its not the exhaust gas burning it. a line in crayon or china marker works too.
Grumpy Jenkins taught me this when I was in high school.
Nice!
I love how the engine on a stand is in the middle of the living room! Legendary my friend
Thanks 😁
This guy is 100% single,no woman is putting up with a garage full of stuff in the house,lol he’s living the life
Just me and the kido yep 😂
Well I certainly wouldn't expect him to store it outside in the cold garage.
Very good video. You are 100% correct about the scavenging effect and the power pulses. (Same goes for the intake, look at Chryslers ram induction). Our rule of thumb was to install a collector that was painted, run the engine at about 2500 rpm and see where the paint burned off on the collector. Then we would cut the collector at 3" past the paint burn off area. This was back in the '70's when we were doing this.
You know how many people are arguing with me over this? lol 😆
Here i thought it was common knowledge but hopefully it has helped some people 😂
100% agree with this video.
He's only saying half the story,!
There are positive and negative pulses.
One helps pull charge in during valve overlap and ex gas out.
It also reflects, positive pulse to prevent charge being wasted out of exhaust.
Shorter the pipe, sooner it occurs....ie high rpm
I'm going to leave the chat now, can't teach old dogs etc, just do some reading.
Sorry mate. Same for my other comments, the things you describe must be quirks of such engines ....long header Vs shitty cast ex is obviously better( mostly) but it's not because they're longer it's cos they just flow better etc.
Please research exhaust theory......I was going to say nowt else but it's so irritating...... you make your engine faster etc no doubt but you just guess why!
Sorry.
@@peterjohn3180 i know there are math involve and the length for the pulses. there is a spoon civic that the runner itself cost more than the car itself. its so long that the entire engine bay need to be refitted to include the engine relocated so the exhaust runner could fit in. ruclips.net/video/j9p24qIjWSQ/видео.html
This is literally the best explanation of exhaust scavenging I've heard. And I'm 53. You nailed the laymens terms explanation method.
I tried to make it easier to understand for the "New Guy" hence the channel name 😆
ruclips.net/video/1CzGFoXwrfo/видео.html
Did one for if you are running forced induction!
As a 65 year-old hotrodder, you explained this well and correctly. However, I never uncorked headers to gain power. I only have raising hell and making noise on my mind. Is that bad?
Absolutely not 😂
All good with that!
Bad? Not in my mind!
Only if you do it at 3:00 am after s night if drinking and then do a burnout in of a friends driveway. Not a good way to score points with the friends parents. 🤷♂️
@@danmyers9372 I like your style! At 65 I still raise hell but none of the parents are still alive. Come to think of it, almost all of the real hotrodders in this area aren’t either. But your idea is solid!
Hey, you know what youre all about and thats important. Some people dont know WHAT they want in life 🤣
You are 100% correct. Back around 1974 I took my street driven 1970 Mach 1 to a test n tune. I uncapped my street headers and fought with the car all day. It definitely lost torque and was running a good 2-3 tenths slower than what it ran on the street. Being an ignorant kid I tried rejetting the carb, switching carbs and changing the timing all to no avail. It was a turd, especially down low. If only I had had some bolt on collector extensions!
You dont know what you dont know lol 😆
Hopefully this video will help some people 👍
A turd sandwich or a giant douche
You are mostly correct but there is one part you're missing, scavenging occurs because of a pulse that is sent backwards whenever the exhaust pulse reaches the collector, think of it as a ripple in a pond bouncing back after hitting a dam. Basically you are trying to catch the vacuum on the bounce back, which pulls the air into the cylinder over exhaust and intake overlap, thus creating scavenging. This only happens over a short rpm band, and this rpm band is determined by the distance from the valve to to the collector, and the longer the header the higher up in the rpms you catch the scavenging effect. Now because it works like a wave there will probably be 4 or 5 peaks in torque that you will see in decreasing magnitude, but if you aren't running high enough rpm it is absolutely possible to have too long of headers and so you won't be catching the first and strongest pulse, instead youll be using the second, much weaker pulse. Anyway I hope this helps someone learn something.
Maybe people should give this a listen, each tube needs to be a specific length and diameter for a given cylinder, and horsepower/rpm range: ruclips.net/video/f72BMpmoGMY/видео.html
ruclips.net/video/FlubSHSFyGQ/видео.html
I did a video on that too 😅
Dang, world of knowledge going on here, this is very interesting.
Sounds very similar to the concept of 1st, 3rd, and 5th harmonics of a fundamental frequency where the 1st harmonic is larger in amplitude than the 3rd and 5th.
Would be interesting to see this on dyno testing
Type in "collector extension dyno test" and there are quite a few videos of it 🙂
That actually makes sense and explains why the H pipe exhaust is good
I can confirm this information is 100% true. My engine on my 73 ford makes more torque with mufflers but lacks the top end power of open headers. When I tried just running open headers I had great top end power but horrible bottom end torque. When I ran 18 inch collector extensions on my headers I got the best of both worlds. With the extensions I seemed to have way more torque than I did with the mufflers and just as much top end power as open headers and a better throttle response. My car is definitely faster with the collector extensions!😁
That's why I made longer collectors to my headers, tapering the pipe down to my exhaust pipes. Great breakdown and explanation of scavenging the exhaust pulses.
I knew this information only because I listened to 5-10 other videos. You, my man, made it almost too easy to comprehend. Very nice.
Thank you sir! Lol 😆
This is very well explained. Another thing here, when the exhaust (gas) scavenging is less efficient, so is the heat scavenging from the head (Referred to as waste heat, QC, in determining thermal efficiency of a heat source, n(efficiency)=W/Qn, or, (W/Qn)=((Qn-Qc)/Qn), or said, Work in Joules over Resevoir Heat (in) (Engine) (Joules) equals Resevoir Heat (in)(Engine)(Joules) minus Resevoir Cold (Header outlet)(Joules) over Resevoir Heat (in)(Engine)(Joules). Increasing exhaust efficiency with the longer header add on also increases heat transfer efficiency and therefore contributes to added power/torque. By increasing thermal efficiency, we can increase the Work (W) produced, and if we produce more Work in Watts...then we create more HP. 746Watts is approximately 1 horsepower.
Excellent description. I've seen older bikers tuning their bikes with a sliding exhaust listening to the tone change. Take an exhaust off a two stroke it virtually stops.
Two strokes need back pressure and scavenging otherwise they're a mess I used to have a Suzuki 250 Hustler X6 1970 it was a fun little bike I'm surprised I lived through it have a great day
When a fella has an engine on a stand in his living room, listen to everything he says about engine building. That’s hardcore. A guy who knows his shit
I've always been told that an 18" extension is the sweet spot on most headers... Thanks for the video!!
Somebody with short track experience would be worth listening to. From what I've read, most motors are happy with a collector in the 10-14" range.
Thanks for watching!
@@flinch622 n
It is all about your engine. There is a racing procedure to get the optimum collector pipe length. I actually read the real hand written instructions by Grumpy Jenkins.
Scavenging effect goes all the way up to the next intake charge (camshaft overlap). Also, you can use white fingernail polish to draw a line on the collector extension. Make a few full throttle passes and cut where the white turns brown.
ruclips.net/video/xfy9aQsIS3M/видео.html
Actually that trick dosnt work 😅
@@newguysgarage6802 Maybe we should meet up and I'll show you how to do it.
I mean im all ears 🙂
Did you watch my video? What did i get wrong? Genuinely curious 🤔
@@newguysgarage6802 Yes, I watched it. I simply added that those exhaust pulses also create a vacuum to pull the next intake charge into the cylinder. That's why camshafts are ground with "overlap" so that the exhaust valve and intake valve are open at the same time. The amount of overlap needed is dictated by the intended use. At the collector, pulses are merged from other cylinders to increase the "usefulness" of these pulses. However, as exhaust gas cools it slows down and becomes a restriction. Optimally we want to keep the fast/hot exhaust gasses and expell them quickly when they slow down. This is done by tuning the collector length. You can guess at optimal collector length or you can get a pretty good idea of optimal length my checking temps on the collector. Measuring temp on a long bare metal collector with FLIR would probably be the best method currently available. However, you can get close with white fingernail polish (the cheap stuff...not extended wear or anything) or you can use temp paint. It's not going to be a sharp line. Remember, even if you apply it on a dyno, we're seeing the result spanning across an RPM range. It'll be a gradient. So start at the beginning of the gradient and fine tune from there.
Yep i have other videos explaining overlap too lol.
But my point was with the paint stripe actually not working to find optimal collector length.
With the paint trick you will almost always cut it too short because exhaust dose not have to be hot enough to burn paint to still be hot enough to flow.
Only time paint trick is close is when using large primary tube diameters, because they naturally want a shorter collector length so the paint is closer to optimal simply by coincidence 🤔
You should check out the old school Mickey Thompson Super Scavenger headers with the long racing style collectors and mounting flanges for street exhaust systems. The best of both worlds.
That guy knew what he was doing in many aspects of engine tech.
Having an engine in your kitchen gives you more power
Back in the day I put a big block in my 68 Camaro and I had to run header mufflers for a couple weeks until I could save up the money to get the exhaust system done. I swear the car had twice as much bottom end torque after I got the full exhaust system installed. Back then you had to bring it to a muffler shop and have the system custom bent. I ran two and a half inch pipe with a set of Turbo mufflers. I miss that car so much, I should have never sold it!
Still have my 69 Camaro convertible I bought in late 1983. Been bringing it back to life the last couple years. Grandson and I rebuilt the engine last year. We also put in a new transmission , disc brake conversion, new suspension front to back and a new moser 12 bolt posi. Starting to shape up nicely. Been off the road for several years. Understand about missing it. Glad I never sold it.
"I should have never sold it." How many times have we heard someone say that? 😊
Why too many times lol 😆
That was a lesson I learned in my late teens when I bought mine. ALL of the older guys back then all said that same thing. They all wished they still had their “???” car from when they were younger. I learned from the older generation and said I was not going to be that guy. Now I get to pass it on to my
kids/grandkids.
Nice, mufflers and power, you should convince the HD crowd of this.
That's why when I built my own 3 inch exhast system for my 340 Dart it picked up a very large amount of power. The combination of 3" header collectors and 3" exhaust pipes to the mufflers extended the scavenging effect. Mandrel bends and good mufflers lowered back pressure to increase the flow in the exhaust system at all rpms. My previous exhaust system when really examined at its bends was pretty bad.
You got lucky. Today's exhausts are done on computer programs to give you the maximum performance depending on your engine and the setup you want
My friend had a 1972 Dodge demon we had a lot of fun with that Mickey Thompson 14s up front and 15s L60 15s in the rear with Craig SS all the way around man that was a fun car we had a lot of good times took it to connecting highway if you're from the East Coast you'll know where that's at have a good day
I agree, I ran long tubes and 3' exhaust on my FE 390 and it really woke up compared to what previous owner had them dumping into 2" all the way back. The old Indy cars ran extra long headers, essentially a very long collector. But I also think cam duration has a lot to do with how the exhaust is tuned after the initial dump into a street length collector. The old school high lift cams were not as technical with full duration as engines of today. So I can see why they got the good results they were after by simply measuring where mass heat ended vs newer engines need the math formula. Of coarse we know math formulas can be reliable to get us close but still advisable to play around with different set-ups behind the collector. The small exhaust ports gripe my ass on the Vortec V6 heads. I wish someone would make some 202 style heads for that little engine that could. I hate depending on boost for power. Freaking vacuum cleaner sounding POS that won't last 100,000 miles if you drive them hard. Just my opinion.
Great video! You should make another header video that describes the physics how exhaust manufacturers & many authors concluded short collectors are favored for horsepower and longer for torque.
Smokey Yunick mentioned in his book Power Secrets how tricky in his attempts with exhaust,
He actually figured out ways to find natural low atmospheric pressures under the chassis of moving race cars and "dump" header pipes there. He was genius in many "waste not want not" hp gains.
Its alwase better to be to long than to short with collectors.
The power lose from being to long is verry minimal but the power lose from being to short can kill all of your bottom end.
Not to many cases were you would give up 50 foot pounds below tourqe peak to gain 10 hp at the top 😅
I read his book. He did some good work.
Learned most to use the longest rod I could find.
Currently collecting the parts to build a rat rod, I appreciate that you not only identified the problem but also offered the solution, that info will be put to use on the build, thank you 🤙🏻
Hey I'm glad it was able to help out! 😃
Back in the day I ran my 69 Road Runner with full exhaust but where the headers met the collectors instead of a gasket I put a washer in between the bolts for a little gap. That seemed to work fine. A lot of Mopars in the Washington DC area back then ran like that.
Weird idea, but I think i can see how it works.
Velocity of exhaust pulse jumps straight past the breather gap, and if the vacuum behind the pulse is too great it draws air from outside to keep the velocity up in the pipes I take it. Now if I'm right about that, that's bloody clever and I love the idea! However I'm no exhaust expert, I'm just trying to make sense of it with my limited knowledge of physics
@@YouNameItGaming how does introducing outside air into the system that goes back against the flow increase velocity? Further more at that point you lose the draw of the hot exhaust pulling the burned gasses out of the cylinders and the valve overlap ..when both vales are open at the same time drawing fuel and air loses some of its effect ..well actually what happens is the lower pressure that is created internally or vacuum from escaping exhaust leaves a void that the atmospheric pressure above the air intake tries to equalize it forces its way in and if you have x about of space that has air moving thru it and then the space is reduced the air behind continues to push meaning in order for the air volume to vmcontinue it has to speed up ..the velocity effect ...
@@jamesgibson5876 "how does introducing outside air into the system that goes back against the flow increase velocity?"
It doesn't. Nobody said anything about increasing the velocity!
Like I said, I'm not an expert in exhaust, I'm just trying to make sense of how it would work if indeed it does, and the way I speculate that it would work is if the exhaust pulse carries momentum down the exhaust tube and follows a similar principle to a bullet in an insanely long barrel (expansion completes whilst bullet is still in barrel, the momentum of the bullet creates a partial vacuum behind it, bullet loses velocity) and so allowing air to enter behind it in such an event would in theory reduce the the partial vacuum behind the pulse and reduce the potential for lost velocity.
Now to be fair it could lead to a reduction in scavenging, but I simply do not know
Now once again, I'm no expert and I could be and probably are wrong, but you're clearly not looking at it the same way I am
@@jamesgibson5876 It doesn't. Using washers is just to make more noise without risking a ticket for not running an exhaust.
Round of applause for this man . Very good sir
As long as those headers seem I’d guess they are for around 4500-5000rpm at that diameter, often will try to incorporate two pulse per runner before the collector for higher rpms in some theories but using theory and formulas only goes so far, as nothing beats making it and testing it, the best I’ve seen is 8-1 system with an adjustable length collector it makes an ol gm v8 sound like a formula 1 engine
Yeah I saw a mini modified puller tractor back in the mid '80s with an 8 into 1 that screamed but seemed to do better than the 2x 4 into 1 tractors with the same capacity SBC
@@barryduff5058 yeah the few I’ve seen were pretty well tuned and were fastest of their class
Most of the tuning I've done internally on my engines is cheap free horsepower take your pistons and balance them take your sharp edges in your motor & chamfer allow for good air flow allow for good oil flow run high Volume oil pump but the price of the pump is worth it saves you from losing a motor and the main thing port and polish you're intake it's simple get your sanding rolls and a long extension polish it out match it to your heads with dicem blue and you'll get free horsepower also make shore your rotating assembly is well balanced and it's real simple have a good day
Port.....but not polish lol
If you get the intake verry smooth then that lets the fuel come out of suspension and puddle up along the port walls.
On a carburated engine anyway.
@@newguysgarage6802 yeah it’s a complicated topic and it’s different for different parts of the port, and can be counter productive in the wrong place causing more fuel to come out of suspension than a completely polished port Eric weingartener has excellent porting videos and has done some testing with golf ball ports from memory should not be done on the port short side
I love these type of presentations.
-Gas column velocity
-Scavenging
-Wave form tuning
Thanks for this video. This gives me ammo in my arsenal to send my buds who are just not educated on the science dynamics behind what exhaust actually does to performance.
You are welcome lol
Ya there seems to be a lot of that from what im reading in the comments lol 😆 😂 😅
Hey Buddy, in the 70s,I use to make, what us Kiwis called, freeflows,for various models of cars. Every pipe has to be the same length, no matter what room you have under the bonnet. When finished, I tested them by blowing air down each pipe, and holding a cigarette paper over each other hole, to make sure that they all sucked the paper out. Works everytime .Loved your presentation.
You are partially right ! The fuel/air mixture enters thru the intake valves scavanges the burned gasses, passes thru the exhaust valve and cools the exhaust valve on the way out. Valve overlap duration, header diameter and length, intake diameter and length needs to be all in tune. A portion of that fuel/air mix that is now partially in the exhaust reverses direction by the pulse of the next cylinder exhaust. That pushes back thru the exhaust valve and back into the cylinder along with the incoming fuel/air from the intake and will increase the cylinder volumetric efficiency. An open header will reduce the double charge efficiency of all the cylinder. Some back pressure is necessary to improve torque and hp.
I want a cold intake. Please use water to cool the stem and seat of the exhaust valve. Scavenging is to suck out the heat early and to suck on the piston surface while it moves up.
I learned something @ 44 yrs old. And I have been around hot rods my entire life thank you. I have so many more questions for you.
That is probably the best explanation of the scavenging effect I've ever seen...thank you for that...
Thank you for appreciating it! 😃
But its really inaccurate. There is a BIG difference between tuning and understanding fluid dynamics.
Its dyno proven lol 😆
@@newguysgarage6802 Dragsters and funny cars have short, stubby individual pipes because they REALLY make power. Same for airplanes in WWII if they didn't turbos. *The KEY is matching the flow rates of the intake **_with the exhaust_** AT the most operated RPM.* Think about this - how often is a street driven hot rod operated at wide open throttle? Not too much, most of it is at cruising speed with some hard acceleration now and then. How often is a legit race car driven at half throttle? Almost never if it's a top fueler. For a V8 street car the _best_ option is not a '4-into-1' but a tuned crossover OR 'tri-Y' header with a dual plane intake because it has the best wide range of RPM flow characteristics ... unless you're literally drag racing from stop light to stop light but that's going to get you arrested.
.......you are misunderstanding why dragsters use zoomies.
They are supercharged and running a high volume fuel.
On supercharged engines air is getting forced into the combustion chamber and during overlap pushing the exhaust out.
The reason scavenging makes power is because it is helping pull the intake charge into the cylinder during overlap. On a supercharged application that is not necessary and as such exhaust scavenging is less important.
At a dragsters level were they are also running a high volume fuel along with that all they need is to get as much out as possible AKA zoomies.
Now radial engines, they do not use headers as we in the car world would recognize because of packaging restraints in the airplane itself.
They make about 1,200hp which seems like a lot until you realize they are 1,800 cubic inches..... thats like a 302 making 250hp....stock manifold territory....
In 76 I built a 390 4 barrel for a friend with a 66 mustang fastback and stuffed it in with headers for the exhaust i had a muffler shop where a friend of mine worked make up a custom dump gate aimed down and out you could either run standard duel exhaust or uncap the turn outs so he could make a LOT of noise .his neighbors hated that car but at night the fire coming out of those pipes and hitting the pavement at the local car hang out was something to see . O to be 18 again .
You can also add a High Flow Catalytic Convertor at the flange on the headers, they give the hot gases somewhere to expand in to in a similar way to the expansion volume on properly Tuned Headers, without restricting gas flow, and clean up the cancer causing gases in the exhaust.
I did this on my GTO and unfortunately that theory doesn't hold true. The car was completely gutless on the bottom without the catback. The converters are about 20-24 inches in length past the collector. Kooks 1 7/8 headers with Hi Flo cats. Put a 3 inch stainless works exhaust on with x pipe and it runs awesome.
@@prowler10393 'GTO,.. brain went 'what model GTO from the '60's/70's had cats,.... then went 'Ohhh, Commodores,...' Yeah, removing the Cats from the DunnyDoor is a bad idea, back to those Aromatic Organic molecules in the exhaust making people sick who breath them.
As for performance, 'gutless without the catback',.. So it had power with the cats in place? High Flow cats have that funnel shape at both ends to expose the whole front face of the honeycomb to the incoming hot gases, which transfer a lot of heat in to the honeycomb, by the time the gases leave the cat they can fit down a pipe easier as they have been cooled by that heat transfer.
This is the best video I’ve seen unlike these other videos. You got straight to the point, Thanks man!
Thats what i do lol 😆
Thank your for watching!
Lots more content coming 😁
A guy giving me advice and insight on header and scavenging technology.......on a header.....on a motor.....on an engine stand in his kitchen. Thats pretty much a ''must subscribe'' in any gearheads book. In subbed.
Thank you!
Yep pretty much checked off all the boxes on that one 😆 🤣 😂
Some David Freiburger energy
I'm I the only one that knows this guy is being sarcastic ?
That was actually one of the better explanations I´ve heard on the issue. Nice, very nice. If I may I would like to add something that might help. The pressure wave that is provoked by the escaping gas out of the exhaust port is just that, it´s a wave. Meaning there are peaks and valleys. Simple so far. If you have an open exhaust those peaks and valleys help scavenging but only a little bit, i.e. you do not generate as much power as you could be. By extending the collector and/or reducing the actual exhaust tip you provide a reflection point for that wave. This new wave has more restriction for the gas flow so the AVERAGE pressure of this wave is actually higher than an open header. But, BUT, this new wave has higher peaks and valleys. The valleys are actually a slight vacuum and as the new wave has a LOWER valley it´s pressure is actually lower than the valley of the open header. It is this lower pressure (valley) of the restricted wave that provides more of a pressure differential during valve overlap. This higher differential forces out more of the remaining spent gases and that leaves more room for a fresh charge of air/fuel mixture. In other words, if you want more power you need more air/fuel in the cylinder BUT before that can happen you must first evacuate the spent air/fuel from the last power cycle. Provoking a higher amplitude wave by restricting it a bit gives you higher peaks and valleys and that equates to more room in the cylinder, i.e. more power. So if you say you need back-pressure you are correct and wrong at the same time. There is no one, single pressure in an exhaust system at any one time. Rather, they are full of waves (peaks and valleys) and it just so happens that the wave with the HIGHER AVERAGE PRESSURE provides the LOWEST pressure. Hopefully that makes sense.
hi, i used to race on the Atacama desert with my nice patrol v8 and i always used long headers (not that long as in the video, because they didnt fit), but i did run a tube between both sides, joining left and right after the collector and the torque gain was huge. I think the old nascar cars made this too :) (im not an expert, but read that in an old hot rodders forum). That compensate both sides of the engine and it was very smooth, considering the cams i did use. Im kinda old school. :). it was a 2 main bolts 350, bored to 355 with 10.5 compresion, arp bolts, alu intake, rods, flat pistons , crower cam, lifters and a small edelbrock carb ( i thing it was between 500 and 600 or something like that) with an offroad kit (this kit was awesome). Very nice video explaining the scavenging effect. At the end it comes down to where do you need torque/hp in the powerband. I could bash 40 degrees dunes without having fuel issues and i didnt died, so i think it was a good combo :D.
Yep!
Connecting both sides of the engine together is essentially a second collector allowing pulses from one side to help pull out the pulses from the other 😁
Er..... 5 inches over bore? I've never heard of such a thing on a small block ...hell you could get five inches with a hone...as for 500 or 600 ..what ? Horsepower? On a naturally aspirated engine your going to work very hard to do slightly better than one horse per inch and it won't be cheap. So 500 or 600 seems sorta uikley ..
@@jamesgibson5876 Hi, CFM, these numbers comes after Carb... :), the engine was .030 overbored. The engine was used and not in the best condition initially and the pistons where a gift from a friend :D. That was in Chile, where we cannot buy easy a v8. It was very difficult to get that motor. hp... well, 5 here, 5 there, at the end i wanted reliability and 320+ hp, from an engine that was originally 210 hp and the most important thing, it cannot die in the middle of the dessert with hi temps.
Found an old video :D. Carb and suspension wasnt set yet. ruclips.net/video/5Fyns2gXMl0/видео.html
found other video :) ruclips.net/video/0Jr8GKtPXoQ/видео.html
I used to run a 383 stroker motor dome Pistons basically a 350 with a 400 crank man great little motor get a lot of horsepower for the whole deal with basically stock parts you modifications but it was worth it I'm 69 years old & old school I worked in a machine but did most of my modification in my garage with simple hand tools have a good day
@@jamesgibson5876 I think he was saying .005 or .006 so before we used to run our bores a little bit loose not quite that loose we went more like three or four just to get the motor to run good without too much resistance on the cylinders have a good day
62 year old son of a former drag racer. I never ran open headers. I had a buddy of my Dad weld up a collector with a wedge to help scavenge an bolted a high flow glass pack to my 428 Cougar. Never noticed even a tenth at the track.
All engine combinations are different. My old supercharged sbc hated exhaust of any kind and didn't care about any length of extension on the headers. But I also know guys who pick up a tenth or so with extensions. Experiment to see what your motor likes.
I have a boss 302 engine in my 68 F 100. Makes plenty of torque with 5 inch diameter collectors made from a dodge drive line.
Like you said. Every engine is different.
You are exactly correct!! 💯
@@jesse75
Lol to let you know how crazy overkill that probably is the downpipe on my 600hp turbo Coyote is one 5in pipe and it's probably still overkill. But whatever turns your crank.
@@177SCmaro I've got them hooked up to motor home mufflers. It's pretty quiet. All you hear is the motor..
Been in my truck now 35 years.
@@jesse75 nice
Good video.
A heart murmur is similar and for similar reasons. If the flow becomes turbulent at the heart valve (exhausting), the result is poor flow. Poor flow robs efficiency and creates a loss of power and a suffering of output.
Engines from air induction (air cleaner/filter housing/or air horn/hat etc) to the end of the exhaust pipe and everything in between needs to be built around each and the total. Not doing so is a crap shoot and ends up being mostly chance that you are not leaving power on the garage floor/workbench.
It's a fine line between the art and science.
It takes science, and the true artist, knows how to use the science to the fullest.
Those are the folks that win consistently over time.
If u watch engine master they proven open header make more power on the dyno. If you not seen it u should. Just my two cents
They used a cutout, which came close, but, they didn't test a 12 to 18 inch extention designed for scavenging...true extensions would have made the most torque...
S5 ep.69 they did extension testing
They did an entire episode on extensions, ,conclusion, at least 18 inch stub. After 24 inches ,no significant gain on hp/torque, or backpressure increase. Need to rewatch. I do know this my 427 AFR Headed SB stroker, 60 fts a little quicker with stubs, as opposed to open headers. as well as a slightly better ET.
Thank you for this and it reassures that what they did at the garage where I got my open headers on my Chrysler 5th Avenue was the best set up! It's a very lean burning car with very little horsepower, but it just sounds amazing on the open road!
WHY do people keep mis-spelling 'lose'?
The opposite of 'lose' is win, or gain.
The opposite of 'loose' is tight.
Lesson over.
I agree with the comments below that say it depends on the setup, and also that long tube headers don't always make more power, thats why high rpm engines use short pipes and no collector. Long tubes are usually for low end torque... And I would also like to say that some engines do need back pressure if that is how they were tuned from the factory. Many engines will run too rich or too lean if you just change the exhaust and get rid of the back pressure. Just ask the people who've burned holes in their pistons shortly after getting rid of their back pressure.
.......change the jets in the carburetor then!?
Running too rich or too lean is not a flow issue its a tuning issue! That is the worst excuse ive heard 😆 🤣 😂
Your talking about zoomies on NHRA drag cars they are supercharged.
Supercharged engines do not rely on scavenging and vaccum to get exhust out and help pull fresh intake air into the cylinder on overlap.
Long tube headers are for high rpm not low.
Shortie headers and cast manifolds are for low end around town everyday driving, thats why they are short from the manufacturer.
@@newguysgarage6802 If you say so, I'm just really glad you're not tuning my motors. My 468 BBC at 8500 rpm told me it like shorties, and as a bonus we get to make snow cones with the frost from the tunnel ram.
Me too.
I've tried to tell that to so many people that enjoy the sound of back pressure backfiring whatever you want to call it I'm tired of doing it already
@@newguysgarage6802
Then I guess you're running straight out of the block if that's your mentality we don't need any back pressure we don't need any collecting we don't need any stinking badges
Thank you!!! I FINALLY have the explanation I’ve been looking for. This question has bothered me for years. Great Job 👏
You're welcome 😁
I read an article about exhaust systems and it stated that a simple one pipe exhaust with no muffler would make more power but the length of the pipe would make it unfeasible for a vehicle as it would not be able to fit. Now this is for a stock application and the article was in a Popular Science or Popular Mechanics magazine back in the seventies.
You a tutor for comon sense that was well explained and a golden nugget of true tuning thank you 😊
Thanks for listening to it! 😀
well explained, makes perfect sense and there is always those that "know everything".
Thanks! 😁
Excellent video and explanation!
I do agree this to my surprise is still filled with misconceptions and your video explains a lot real well :) length = helps scavenge I did a drawing w/ animation pertaining to Volumetric efficiency and stated that as soon as the exhaust column exits the tip of the exhaust? The length itself “pulls” the newer oncoming exhaust from the head hence helping “scavenge”
Your words are perfect “you’re not taking advantage of what the header is capable of”
Thank you for this love it!
And I do agree with Mr Meyer on the comments on the intake it’s the same but inverse or the opposite… prolly why “stacking” was used in the term “velocity stack”
ruclips.net/video/1CzGFoXwrfo/видео.html
Thank you for watching!
Also when you add forced induction into the mix everything changes lol 😆
@@newguysgarage6802 that’s soooooo true on Forced Induction suddenly mr Plenum is worth a minute 🤣
Honestly have not done any kind of tuning on gas engines, and never heard of scavenging from exhaust, but I understand and it makes sense now. Nice vid.
That’s great info! I’ve always wondered why open headers lose power but cut-outs we’re fine!
Excellent video, I put header insert mufflers in my 3.5 collectors and got an extra 4 inches of length on a 3 inch system netting 18" before the bend and boosted low torque.
Gotta love a guy who has an engine on a stand in his kitchen! 😂
I've been building winning race engines for over 30 years...and everything this man is saying about collector length is 100% correct. We dyno tested different collector lengths and found that just 1" can make a big difference. Great video brother!
18” is the ideal length, dyno proven for collector extension great explanation of exhaust pulse and pressure waves
Excellent video... out of the many attempts I've seen in here how to explain.. this was the best I've seen... 👍
Thank you! 😁
I'm glad to see I'm not the only one with engine parts and rims/tires in my kitchen.
That is were they belong when not in use, that way they are on display 🤣
Tomorrow my Cutlass is finally going to the shop to get longtube headers installed, thanks for all the help and for checking out my video to see if they’d fit. You are awesome! ✌️
Awesome!! Im glad your making progress man 😃
Finally a smart man, I've been arguing all the old heads I know that you don't need back pressure since I was 16 and straight piped my Chevy
Nope no backpressure at all lol 😆
People confused longer pipes with backpressure when really its scavenging!
Contrary. I actually lost power running an exhaust over open headers.
Fair. That being said, I run a supercharged motor. And Scavenging on a N/A motor is so much more important it can be considered second-nature at this point, to the end of Scavenging and Backpressure being used interchangeably, as in order to get scavenging, you need channeled/directed flow through a restrict or that creates fluid adhesion to create a vacuum.
Additional. “Backpressure” in the 4-stroke world doesn’t mean the same thing as “Backpressure” in the 2-Stroke world, as 2-strokes need specialized exhausts that create actual restriction to create enough vacuum for scavenging to take place. Backpressure (referred to correctly), in both applications is just a way of directing and funneling flow to create a scavenging effect. I could go on all day about Camshafts and Lobe Separation/Overlap, but I’ll leave that for everyone to research into and make their own conclusions on. It’s real simple, the information is out there and it’s the sorta information that wins races when the finish line is determined by 1/10th of a second of acceleration, and it’s decades-old knowledge as well.
Conclusive. The confusion comes from a mix of fundamental misunderstanding of fluid dynamics, a fundamental misunderstanding of 2-stroke motor operating principles conflated with 4-stroke motor operating principles, ego (on both sides to some degree), and the absolute fuckup that is the English Language.
You are absolutely right brother right on I had arguments over this issue a while back thank you old school
Im having arguments over it now lol 😆 😂 😅 🤣
But hopfully this will help more people get more power out of there hotrods!
Thank you for watching! 👍
The engine in the living room tells me this man knows what he is talking about. Great video
Thank you sir! 😁
And thanks for watching 😃
I didn't really understand the wording but I understood that the manifold actually works collectively with the engine to pull the exhaust out. So I knew long tubes with longer straights after them worked better than short tubes or street long tubes with no extension. Couldn't explain it well to my friends so this video is going to them for the science!
Nice! 👌
Ya sorry about my vanacular why of speaking lol 😆
Its harder in front of the camera 😅
The tube length is a frequency thing. The length can determine if you get a 2nd order harmonic, 3rd order, etc... (imagine stretching out a slinky between your hands, then twitching one side. You'll see a tight spot go back and forth until it runs out of energy and fizzles out. Same thing)
The reason you need is collector extension, is because the collector can't do it's job, if an inch or so later, it dumps to atmospheric pressure. When that happens you no longer have a low pressure area at the other 3 tubes. When you have around 18" after the collector, that gives you about a foot of area to have a 'stretched spring' of air in there. And that 'stretched spring' is there pulling on the primary tubes.
Thanks for finally doing a video on a topic covered in Hot Rod magazine in 1984.
Your welcome lol
Good advice. Header collector extensions are a proven way to increase power.
I did a similar thing with my 2 stroke motorbike, i extended the pipe and narrowed it down!
It lost low down torque but loves the high revs now!
Wow, thanks for sharing your knowledge. What happens if you have that open head without any header or manifold?
Will barley run, and you can actually burn the exhaust valves doing it 😅
Clear explanation with no fumbling and stumbling. Good job.
Thank you sir! 😃
Well described and beneficial for noobs but I have to partially disagree. You have two sonic waves occurring, one at the end of the long pipe where the wave bounces back to the valve, and then returns, and a second sonic wave bouncing back form the rear of the collectors next opening. That's why the collector (or expansion chamber) also benefits from being tuned length to the pipe diameter/volume, speed of sound and the required Nominal RPM. Obviously the length (tuned RPM) of stock long pipes cant be changed so you need to match the collector either to a short dump (Large longer pipe), or a long tuned exhaust at the end of the next stage usually at a muffler using the short adapter (in this case the second sound wave bounces off the tuned location of a muffler. The pipe size is also important as you need to time how much exhaust gas can be drawn through the pipe before the next sonic wave and vacuum cycle.. A full tuned exhaust will have multiple sound renascence points. A muffler will also act as an expansion chamber or resonance point. It's all about the sound length and total volume of each stage which is matched to the desired RPM. You can have 1 x resonance length, 2 x resonance length and so on. Long resonance length usually smaller diameter pipe, larger diameter pipe = shorter resonance length, but its all a balancing act.
>
It's complex stuff to work out but Phil Irvin(Engineer) describes all the formulas quite well. I think it was in "Tuning for speed".
Never learned exhaust theory this way. Thanks.,😂
Greg---'63
I showed this video to my wife. She thought I was the only one that kept a hot rod motor in the living room. Had a S.b. 2.2 in front of my T. V. Till the rest of the ride was ready.😅.
Nice! 🤣
I went through this with my wife's Mach 1 Mustang and Flowmasters vs Magnaflow and I can tell you there was a seat feel difference. The Flowmasters had more seat feel than the Magnaflow. We think it was from the back pressure from the baffles in Flowmasters. 🤔
Probably!
That feeling that you were getting. Are you sure it wasn't that drone that Flowmasters are known for? Especially in a Mustang where they placed the muffler. Depending on the year I've seen many in the middle of the exhaust pipe. Normally we would expect to see them at the end. Not in the Mustangs that I've worked on back in 2002, 2003.
Thankyou for explaining what I couldn’t quite get my head around I thought this was the case with open headers but wasn’t 100%
I owned an exhaust shop in Tn. For 17 years. You are exactly right. I use to tell people to run atleast a 12 inch extension off the collector. On our drag car we also scavenged off the valve cover to the backside of the collector.
Nice!
Ya ive been getting a lot of push back on this one lol 😆
Thanks for watching 👍
1:14 No vacuum is created, just moving exhaust gases create a low pressure which helps the next pulse of exhaust to come in behind it. If it were a vacuum then the exhaust wouldn’t move down at all. It’s not correct to say the standard car exhaust manifold doesn’t scavenge, of course it does, it just can’t do it as good as extractors or high performance pipes will, is because the car manufacturer has to compromise between fuel economy, usable power at large rev ranges etc, a race setup has to forgo fuel economy naturally to achieve high hp, which is why these pipes will suit this style of driving. But you can’t have it both ways. A daily driver will have back pressure simply because of these compromises and the manufacturer has designed it for peak performance and economy for those conditions. Yes those pipes can be way shorter, top fuel dragsters have foot long pipes at most pointing upwards, whatever gets the result for that particular engine, the longer pipes aren’t better or worse, just depends on when you want that power range to be.
I read this in a book 50 years ago and the book was 30 years old at the time. The English had it all figured out and there was a magical number for the length of the pipes and for the life of me I can't remember. It was either 36 or 38 inches long for the open headers to give optimum power. Y'all probably know it though.
It changes with every engine.
You have to take the total flow of the exhaust port and match total exhaust volume to it for optimal tube filling........................but for us that dont have the means to do that "18 is a good average for collector extension length.
Its always better to be to long then to short.
The power lose from to long is way way less that the power lose from to short.
Nonetheless there were still people that run any exhaust that makes their engine louder that's their reasoning the louder the better that's all they're concerned about not talking about everybody but there are many out there that believe this
Hat's off for taking motorsports so seriously that you have an engine in your home. Respect.
Lol 😆
Well its the warmest place ive got here in MN 😁
@@newguysgarage6802 I got ya". I live in Canada and had my motorcycle in my place all winter a few years back. Why leave my baby outside? That lowers the resale value.
Yep 😁
Yes you're 100% right my son and I used to race a Z28 1976 circle track that made a difference that little piece of pipe have a great day thank you very much
Thank you for taking time to watch it 😁
Great video. Would also like to add that when exhaust gases rapidly expand they cool down therefore slowing down.
Yep!
Add the correct exhaust makes a huge amount of power. Just like expansion chambers turn a 2 stroke engine into a beast. 😅👍👍😍
I'd say Engine Masters did a video that handles this by actually demonstrating with real numbers to answer this topic.
Just seeing that manifold is reminding me of an argument I had a with a guy about the difference between a manifold and a header. The guy didn’t know the difference and was trying to argue that it related more to how much power it made than the design of the part. Power is a byproduct of the design.
I have seen this happen on some cars, but Different combinations are different. Most guys uncork at the dragstrip because they have timeslips to prove it works, they may loose torque especially without an extension pipe, but most make up the difference in the top end of the 1/4 mile We ran a 440 six pack, HUGE cam, Open headers were worth a full second over high flow manifolds with cutouts. Removing the exhaust and running open headers no extension pipe, 3 tenths quicker than corked up with 2.5 inch glass packs. All my mopars had similar results, 383s, 440s and a 400. Even with 3" exhaust. Extension pipes would certainly have helped. But weren't easy to install around the torsion bars. In my many years of drag racing, none of my cars, my dads cars or my friends cars went quicker with exhaust on, and I ran straight thru mufflers dumping ahead of the axle. I now have 3.5 inch exhaust with 4" mufflers. Dropping the exhaust out just saves weight, but doesn't slow the car. But I would gain from tuned extensions. Alot of torque loss actually can come from leaning out the engine sans mufflers. We dialed in the timing and carb on open headers. Definitely ran rich on mufflers. I can prove on a dyno and at the pull track or dragstrips that tuned extension pipes work. Also, we went from dented, beat up $75 1-3/4 blackjack headers to $600 tuned length 2"primary tubes, 3.5 collectors and went 4 mph faster but 2 tenths slower! Lost all that torque in the first 60 feet. Should have had a 3" extension pipe.
Open header is better than an actual exhaust system ya!
But this was more comparing collector extensions vs open headers 😅
If you think of each pulse as bingo ball bouncing off of each other in the short header and creating 'turbulence' verses each pulse escaping the pulse zone individually on the long tube. The part about creating a vacuum totally drove the image home for me as well.
You can always tell how happy a man's marriage is going by the number of motors he has in the kitchen.
Thanks for the reply, I am rebuilding my 460 motor payed for my new headers. So it’s going to have the power,it being a 460 and all well see ya next time see ya bye.
Next you should teach everyone how to get the optimal collector pipe length for power & torque. When I was in high school I read the hand written notes on how to do the procedure from Grumpy Jenkins. All engines are different and have different lengths.New sub. I’m old school and been a mechanic for 40 years and work on big trucks for a living.
The only true way is just trial and error lol
Start long and chop a little off until you run your best ET
The old paint trick dosnt work...so that is basically the best way of doing it is just by going out there and making runs 😅
If everyone explained stuff like you it would be much easier to learn things.
Dang! Thanks man I truly appreciate it 😃
Thanks for watching 😁👍
NICE VIDEO!! I think this video has to be the best clear explanation if've ever heard on this subject. Awesome job. Thanks
Thank you for watching 😁
I appreciate it! 👍
You know it’s real when the guy has the motor in the living room
Thats right 😁
In one of the books that hot rod published in the 60s they have a chapter on how you calculate your exhaust system
This makes sence I have longtube headers on my 87 4Runner and they always come with that collector extension I figured it was just so you can bolt and unbolt the rest of your exhaust more easily it’s nice to know it actually helps scavenge the exhaust the headers alone with a 22re you can definitely feel every hp gain
That one I had is just for coupling the rest of the exhaust together 😅
You would want one that is 18" long (that seems to be the best average length) and have it the same diameter as your collector 🙂
Just on your excellent explanation on exhaust scavenging, I subscribe to your channel.
And you are right.
Those of us that know....know...lol😂
Thanks man! Welcome aboard 😃
While I knew everything that you explained, I really appreciate the simplicity of your explanation. An engine is an air pump. More in, more out, more power.
From what a pro drag racer told me, there's a lot of math goes into all that depending on several engine parameters, chiefly engine speed.
Open headers make more noise, noise=power. Lol
Right out of high school I worked in a shop with chassis dynos. It became apparent that noise DOESN'T equal horsepower pretty fast.
Great video!
Thanks! Lol 😆
Yes way back I saw a car take off at the park who was making all kinds of noise but he wasn't moving very fast. I think it was a 68 gto
A similar problem happens with motorcycle exhaust. It's called reversion. When you're running an open exhaust, we put a "lollipop" in the end. It stops the reversion, and you still get the flow and the power. Also, your house looks like the inside of my house. Instead of an engine on a stand, there are motorcycles.
I consider myself a fairly competent car guy until you bring math and physics into my garage. Great explanation, it does make sense
Thanks 😁
They can fight all they want but they can't fight against information that makes sense.
While Engine Masters has taught us:
*Theres a 1 to 2 hp difference between long and mid length headers.
*Header extenders gain 3 to 4 hp more.
*Theres a 1 to 2 hp difference between X and H pipes.