This really only explains the piston speed limit, though. In most cases, the actual limiting factor is valve float. For the bottom end, the limiting factor is ring flutter. If your piston changes direction too rapidly or your rings are too heavy, they lose their ability to conduct heat because they lose contact. They overheat and swell, which reduces ring gap. Once your gap hits zero, you seize and break stuff. Lighter rings and wider gaps can help you exceed the conventional 4k fpm rule. For the top end, the reciprocating mass of the valvetrain, aggressiveness of the cam profile, and strength of the valvespring determine the float RPM. This will usually hit before the bottom end RPM limit in a SBC because lifters and pushrods are so heavy.
I am 62,,,been master tech most of my life. But I have to say I really enjoy ur videos. I'm thinking I learn something every time I watch one. I thought I knew everything about RAT motors cylinder heads. But I learned something from that video as well. Thanks,
I saw this video about a month ago. Great information. Thanks! HOWEVER.....I thought, "Where did the magical divisor of "6" come from and what is its unit of measure"? To go from inches to feet, you MUST divide by 12 (12" in a foot) not; 6. Then, it hit me last night. "Revolutions per minute". A revolution is a full cycle, both up and down of the piston. So....you really must add the stroke up to the stroke down. For the 302, it's 3"+3"= 6". Then, multiply by 7,000 RPM to get 42,000 inches of travel per minute. Now, convert from inches to feet using the divisor of 12. You get 3,500 Feet per Minute....not Inches per Minute. Yes, it's the same answer but, that's the correct way, in my humble opinion, to follow the units of measure. He used 6 (half of a foot) because he only used half the cycle (the up stroke). Now, why is 4,000 FPM the magical number? It seems to be factual but, why? I can't see my 1973 302 turning 7,000 RPM.
Awesome, thank you. I've asked all over the place for a max RPM on my Ford 400 that I'm building, I went with my gut of 5900 max with a stock bottom end (4" stroke) and hypereutectic pistons. With this calculation, 6000rpm is exactly 4000fpm. Subscribed, thank you.
Joe cook, Joe, what engine are we talks about? How many cylinders? Valve train design? Overhead valve overm? Has the rotating assembly been balanced to +/- 1 gram? If you have an oversquare engine you can achieve a higher piston speed before catastrophic failure. This will also depend on if your using cast or forged crankshaft.
I really like your videos; A++. They are packed full of information. I hate going to watch a video for information, and the guy takes up half the video watching him eat breakfast, and then going to visit his Uncle Bob.
Very good info. I've been asked many times, How do you know if you've over revved an engine. My definition is, localized pains in and around the left hip pocket and the realization that your engine will now fit loosly in a 5 gallon bucket. lol!
You just earned yourself a subscriber. Awesome video man. There is a lot of information in this video, but it's not spoken like it's being read from a book. It's broken down into "laymens" terms and it allows almost anyone to understand it. Awesome video.
Believe it or not there is a rule of the thumb that requires almost no calculation at all. Some extrapolation is required as the rule of the thumb part only works for 6000rpm. So all one has to do is know the stroke length in decimal inches, add a zero to the end and voila! 3.00" stroke = 3000 fpm MPS @ 6000rpm 3.50" stroke = 3500 fpm MPS @ 6000rpm 3.75" stroke = 3750 fpm MPS @ 6000rpm I am confident the 4000fpm could be easily exceeded in small motors with low reciprocating mass. An example, for the road going Honda 250cc 4 cylinder Learner motorcycle - the CBR250RR has a 1.33" stroke (33.8mm) and can turn 20 000+rpms. So 1330fpm @ 6000rpm will equal 1330X3 which is 3990 fpm MPS @ 18000rpm (1330x3 as there are three sixes in eighteen - puts you in the ballpark of 20 000rpm. This is the extrapolation bit) I told a mechanical engineer of this and he scoffed. I taunted him to run the numbers which he did there and then and looked up in puzzlement at me and announced "You're absolutely correct." Your equation is ideal for knowing the exact mean piston speed mine is just a simple rule of the thumb one could apply to say talking to a customer over the phone. Great informative vid BTW :)
This video and the one covering camshaft selection are priceless additions to my future engine build. I was given an LS1 from an '98 Camaro and want it to both make good TQ/HP numbers but also give me half decent mileage. I know you can't have both high peformance and high mileage, but there is a sweet spot one can achieve w/ careful planning. Its going to be a challenge w/ the lack of bore-ability of the block, but I should easily be able to hit the milestone of one HP per C.I. w/ a proper balance and assembly. My goals are maximum torque while maintaining emissions compliance, as its my daily driver.
Im slowly working through your videos,and i damn well wish i could actually buy you a few beers,because they are fantastic! I live in the UK,& us chevy lovers are few & far between! Im just considering putting a Gen 5 454 into my 1980 Z 28 Camaro.Thanks again for such great info & videos!
Very good video.....good explanations. I used a 350 Chevy for brackets back in the day with a built motor...good rods, crank, forged pistons, ported heads, bigger headers, good collectors with open exhaust, 5:56 gears, etc. Depending on track conditions I used Victor or aluminum Corvette/Edelbrock 180 degree intake..... If I recall I used a 30-30 Duntov with solids.....it was a good cam because I could open or close the clearance to vary how "big" the cam would be. I would run about 7000 rpm and go thru the eyes at 7200. It held together forever but I watched the tach like a hawk. The car was not licensed for the street. I guess I could have been more radical but this was before all the aluminum heads, etc came into being. I think in those days we understood more about how enginces, etc worked because we HAD to figure it out for ourselves with the machinist. Today, guys can open their wallets with little knowledge and end up with a pretty good engine.
This might give you an idea of how old I am. When I was young I had a Nova that I played with. I liked the 283 over the 327, with low fives in the rear end I would run out of motor just before the traps. The 327's would not survive this treatment a couple of dozen times. Here's the age part, before all these fancy head I had double humps on the 283's. After each run I would pull the pushrods and roll them to see which ones were bent and hammer the studs back in the head from the rocker arms pushing them out. The 283's never reached the speed on the piston to destroy its self or throw the rod and the extra weigh from the 327's piston would grenade the rods. Your explanations over the last few weeks is the best example of why this happened. I really like what you are doing for the, shall we say less experienced persons like my self. Keep up the good work, and yes I grumbled to about the machine work. But the better it is engineered the longer it lives. BEST OF LUCK FROM SOUTH FLORIDA...
Aaaa yes I remember those days my first drag car was also a nova I built a 307 bored it .060 over and ran camel hump heads with a 310 duration Isky cam hooker headers and a big Holly carb I never had good power brakes because of the cam no vacuum booster! I know it sounds silly to build something like that now but at the time it was all I had and it ran pretty good for what it was I ran mid 14's all night long and never hurt the engine my gear was a 456 and I would hit 6200 RPM at the traps I've since had much faster cars and much more powerful engines but that 307 nova is somehow still my favorite car there was just something about Friday night drags back then lots of garage built Ford's and Chevy's, Pretty girls, and not an import within 50 miles those were the days thanks for this post you just made my day!
Myvintageiron7512 Wow that seems like the hard way to run 14's. My Nova has a rebuilt 350 (actually a 355) with 882 heads, dual plane aluminum intake, quadrajet, and a .435/.435 270 duration performance "RV" style camshaft that runs 14s with the factory 2.73 gears in it. Those gears also allow me to take it on the freeway unlike those 4.56s. Also runs in -10*F and +100*F ambient temps without issue. Oh and I still have plenty of vacuum for stop and go traffic ;)
well you see back then I didn't really know what I was doing and building a 307 was proof of that the thing is I was 17 and I honestly think I had more fun with that car than any other car I've owned or built even though I moved on to much bigger engines and serious drag race cars The Nova was my first and there is just something about the first time.
Myvintageiron7512 The best way to learn is through experience! I also here you about the first time. I made the mistake of just bolting on a single plane intake manifold and mechanical secondary 4 barrel carb on the inline 6 in my first car. It was impossible to tune. Sometimes it would shoot off like a rocket but often it would bog, never could get it to run quite right. But when it did go my little four door could blow the doors off 5.0 mustangs and most older fbodys through the 1/8mi. I've learned from my mistakes and that's why my Nova has a dual plane (Weiand) intake and a vacuum secondary carb (quadrajet). Ok, so there was a lot of engine building theory studying going on between then and now too. Keep up the great work on this channel! You've been verifying I built the motor up in my Nova correctly. I'm looking forward to hearing this stroker motor run.
@@Myvintageiron7512 Yep, I was drag racing at 20 years old in my own car. I left home at 15, got myself a job at the local garage and never looked back. It was 40 years of automotive. I'm still mad at myself for not building a serious Nova.
thanks to reducing equations we can simplify (r*s)/6=4000 for the purpose of finding a target redline speed into 24000/s=rpm so simply divide 24000 by your stroke in inches to get the exact redline rpm.
Exact stroke for max rpm of 7000 is 3.4285. What's cool is I just got my hands on an engine only made for 4 years 5 if you want to get technical. The stroke on this 383 is 3.380. So I have 0.048 to work with. Gets me thinking about the engineers and what they were really after. How about something that can be mass produced for intended use but, with a little modern (modern being used broadly, modern is just the time) technology for final touch up work. Can just sit happy right where a street RPM band engine should be for a V-8.
The issue is most production V8's are cammed/intaked to make power between 2-5k, after that they fall flat. If you change an engine to make peak power 5-8k customers would think its too sluggish or too much power pickup in the top range making it dangerous for inexperienced drivers. Its a tradeoff they had to choose reliability and fuel consumption rather then power
Ariel Lezen So since the tach is driven by the cam, every cam rotation the distributor tells the tach to double the amount of revoltions because the crank is 2x the speed of the cam ?
Great info that is data based. This equation takes the guess work out of what people assume is safe. Great articulation and explanation. Great job on the video. Thanks for taking time to offer this research.
Until I had watched your video I had naively assumed that the connecting rod length was almost entirely a side load issue. I had not realised that it also had an effect on dwell time.. you are right of course. It is a shame that people don't always pay proper attention, I cannot fault the information you provide. I think that rather than disputing the facts people should perhaps watch the video a second time, well done on a well put together video.
You're missing the reason for the longer rod!! You understand the higher RPM and stroke reasoning, but the advantage of the longer rod is entirely geometric! A greater advantage is achieved with a longer and more angular focus on the crank increasing the leverage and advantage!
He didn't miss it. All he was talking about was the components and if they can take the speed you are wanting to spin the engine to. The advantage means dick if the internals can't take the forces and become separate pieces.
Good day I am looking forward to rebuilding my 4.0l Jeep motor this summer. Following the formula to figure out my RPM I should be able to build my motor to match the drive train. Thanks for the information and the simple way of explaining things.
When I was younger my dad built a 351W with Cleveland heads, and he swapped over to a solid cam, adjustable valvetrain setup with a lumpy cam. He always told me that a 351 could pull 7000, but I really wasn't sure how that was possible since the 4 cyl in our Focus barely did 7000. Now that I'm following suit and getting into cars, and that I have more knowledge, it's easy to see how to squeeze revs out of an engine. As always, well explained video.
+Ryan Eyster A 351W will turn 7000 it is feesable to go above the piston speeds I have laid out race engines do it all the time you just need stronger internal parts and a much better balance job 4000 FPM is a good safe max piston speed for a stock engine
The Cleveland will do 7000 more reliably because of the smaller crank journals. One of the other things that affects the rev potential of an engine is its ability to reliably supply oil to the journals, and larger journals require a better oiling system to supply enough volume due to the cast-off created by higher surface speeds.
ThePaulv12, no, the Windsor is a wedge head engine, like the 302, that was never as popular for performance as the Cleveland. The Cleveland is a canted valve head, like the big block Chevs. It also has a shorter deck height and smaller main bearing diameter than a Windsor. A 2bbl Cleveland had heads that were more than adequate for most street and racing, but, the 4bbl heads had huge ports that are said to outflow a 427 rectangular port Chevy. These were the same heads used on the Boss 302 and had a very high rev capability due to the flow.
I've seen dirt track racers consistently run 350 Chevy's with stock bottom ends to 7000 RPM but on a few drag race cars I've always played it safe to 6500. Had a 396 once that I would turn to 6000 RPM. But I'm a cautious guy. Great video and thanks for explaining the numbers.
my 409 and 348 both topped out at 4300 RPM. 327-375hp slightly built about eight. But no matter what an engine was rated for I usually drove by ear and feel. Great video's, thanks.
Equation works! My mercury v8 outboard has a stroke of 3.4in, so that means theoretical redline of 7000. Factiry redline is 6200, but the "race" version is 6500.
With this math my Olds 403 could rev to 7,000 rpm. Unfortunately the weak windowed block can handle that. Kinda wish I went for the full monte J&S Halo girdle (did install the 4 main girdle) I'll keep it to 5500 and less and hopefully I don't blow the thing to bits. The 403 bore stroke ratio theoretically is great for a high revving engine, but the block strength holds it back.
Strong internals go a long way here. 4340 crank and fully forged pistons and rods @ 4.25 inch stroke hasn't cared about 7500 rpm in my little hotrod...Yet... Pettis performance builds 598 Chevy (race motors) with 4.5inch stroke that make peak power at 9k. Very informative video!
Hmm, with this formula, the Olds 350 and 403 appear to have a slight advantage over their Chevy cousins with the same cid. The 350 rocket is a highly under estimated engine. Early 350 rockets can be bored to the 4.125 bore the 425 and 455 share, but have a 3.385 stroke, They can also use the big block heads as a upgrade. Even with windowed mains, the 403 can produce some insane numbers.
Thanks, this was a great explanation on how to find an engines recommended redline and performance capabilities. As a side note what is the stroke length of a 5.3L LS engine or would a 4.8L LS engine possibly be a better option? I would like to use a M122 GT500 Roots style supercharger and possibly even use a turbocharger as well.
R.P.M's, i knows MANY mechanics/technicians use plural on minute. I have 2-96 Roadmasters with the LT1 cast iron head, I have no idea of the casting numbers but 2000 R.P.M's with the rowing package gets me 80 MPH all day. I bought one of those tuners to tweak dis n dat and raised the governor from 108 to lotz more and put higher speed rated tires on one of them and now I've been to 3500 R.P.M'$ which is/was north of 130 M.P.H'$ on highway 99. Built a few engines and enjoyed the few videos of yours I've watched. Gene from the left coast near the state Crapitol
351cleavland usually the failure of the end cap or connecting rod bolts ... i.e. ..flies out .. other sources of failures can contribute too .. lack of oil psi to the bearings , cause the bearing to fail .. excessive clearance leads to the "knocking " then excessive heat , gaulling , seizure , boom ... the rod is the last to get oil ..
randysengine service Sure, I did that and a week later a piston flies out the engine compartment into the cabin and up and out through the sunroof! I am 50% sure its not going to bre covered by warranty!
Thank you for your Chevy 350 Video Series. These videos have helped me improving my technical understanding of the 350. Im saving up for my first engine Rebuild or Engine Build right now. ....Best Case scenario.... I'd LIKE to see 600 hp/ 550 Torque out of my current 350. either in the 383ci or 400 ci. but since I still need to iron out other details on the truck. I'm probably just going to do a HO 350 rebuild for now. so I can drive it while I get the other details fixed as I go. I'm considering buying a built crate Engine or sourcing a LS Engine later. the problem I have with the LS Option is. all the little stuff im going to need in order to make the LS work in my 94 S10. Wiring. Engine Mounts. power train. Computers. transmission linkage. cooling systems. yada Yada yada.
I have a 92 S10 myself. As well as a 1970 350/300 4bolt along with a good 350TH to use if I wanted. Same problem as you. The LS option is for sure going to require extensive wiring and what the heck, the speed it is going to generate might as well figure in a suspension as well. Lord knows the flimsy shocks that you get for the S10's isn't going to handle the corner speeds... I'd like to do anything/everything to the 350 and sit it in it, but hate to think that it will be just a putt putt truck...
@LORDdeath Gaming You're making more out it than necessary for an LS swap. The wiring is a simple affair that you just lay on top of the engine, once installed, and start making connnections - it falls together like falling dominoes. I was intimidated by the prospect as well, but it went quite smoothly, once I hunckered down and started the process. As for your plans for your SBC, just remember speed costs money, so get rready to spend a pretty penny for an engine w/ those specs. Just sayin' those are big block numbers. Best of luck.
Reliability/durability of the crank and bearings are what limits rpm, right? They the failing components of high rpms, right? Can you increase rpm and/or add stability/reliability to the exicting redline by using a higher viscosity oil or some kind of racing oil?
Very informative especially for someone who is not a mechanic, but I have a question- If I have a neo vvl St 20 will installing a vvl controller and setting it before 5000 rpm harm the engine? Thanks
Great video, I have a 2003 Toyota Matrix XRS which has a 2ZZ-GE engine that red-lines at 8200 RPM with a stroke of 3.35". By your formula my pistons are traveling at ~4575 FPM. But I guess that is what you do when you are a large corporation and reuse and engine that you put in a Lotus Elise/Exige.
Not to mention, bearing surface speed with longer stroke requiring a better oil delivery to cool the bearing surface. With oil temperature being more critical to making power, the window narrows significantly. The old rule of 10 psi per 1000 RPM may not be sufficient.
I have a friend randy that built a Chevy small block back in the late 80s that saw the far side of 8700 rpms and that thing was a beast, it never came apart , it was in a 69 Camaro, I saw that car beat built 600 hp big blocks , one guy he raced and beat said i heard the horse power screaming out of your grill when you passed me
Here is an interesting fact you may not know. The piston moves faster closing in on and moving away from the top of the stroke versus closing in on and moving away from the bottom of the stroke. The reason why is because of rod angle effectively acting like it's growing the rod in length as it approaches TDC and in effect shortening in length as it draws away past TDC. The distance between crank throw and wrist pin varies with the angle of the rod. Growing in length while approaching BDC, bottom dead center actually slows piston speed down. It may be hard to fathom but the net effect is that there is more dwell time at the bottom for cylinder filling and less dwell time at the top to take advantage of chamber pressure. Learned this phenomenon at the tender age of 70.
Would be cool if you did a video on the effect the connecting rod length to stroke ratio has on the hp and torque of an engine. I've always wanted to build a Bug engine with a 1300 crank and the biggest bore pistons the bore centers would support and then have the cylinders long enough to support 2.3 x stroke ratio. Billet heads with the biggest valves that would fit without shrouding in the bores, and as close to a 14:1 compression ratio with closed chambers and D cup pistons. The camshaft would be tuned to the dwell time of the pistons at the top of the bore. The next thing would be a single plane pyramid intake with a tuned plenum and runners along with a Holley 660 center squirter carb. I know the Euro guys like the weber carbs for throttle response, but a single plane intake with a combined tuned exhaust makes more power overall.... Anyway, would be fun to build such an engine.
+Ray Main You're even getting me excited. Remember high compression = pumping loss. There have actually been a number of very high compression production engines over the years and after the first run they were always backed down to around a still high 11:1. Another thing, by my way of thinking, very high compression is only worthwhile (on the street) if the ignition timing is
how do you determine what the piston speed should be for a engine? example. hp rods and a low rpm high torque cam. over a stock cam and rods. or a high rpm cam and rods.
Now that was informative thanx bud. Ive got a 355 Id say a lil bit more than moderately built .i twisted it to 7500 and 3 of my harland sharps started clacking pulled covers off and had 3 backed off to abot .050 .supposed to be .021 wp heads,1.555 springs,doubles with dampers. Cam .600 in .625ex..rockers actuall hit stud girdles.ALMOST A CATASTROPHIC.
just an educated guess but the reason why you use 6 instead of 12 to go from inches to feet per minute is because the piston travels the length of the stroke twice for every revolution . so really what you are doing is ( stroke/12 ) x 2 which is the same thing as dividing it by 6
I am spinning a 4.6" stroke at 7400 RPM. But as he says, much must be done to be strong enough to do it. Billet crank, rods and main caps to start. This is in a one off tall-deck LS race block. (LS blocks have fully girdled main caps unlike SBC, so that helps too) But that give you an idea of where things can be taken if you want it bad enough.
Sort of off subject but could you explain briefly the designation of Chevy engines. I see references to LT1, LS, Gen1, Gen2. Pretty confusi g when looking for parts.
What I was hoping would be covered in this video was the effect of longer rods on the same stroke...I've seen a lot of guys build "long rod" engines, but are the gains worth the time and effort? I've also read that long rod motors make much better use of small valves and ports, but I haven't come across very many A-to-B comparisons.
Cool information my stroke is 3.6 so it seems as 6500 is the max safest rpm I can go on my engine which is 3900 fpm. And you said the longer stroke gives more torque which is interesting as I could tell my engine was a lot more torquey than my 3800 L36 powered car which according to this formula the L36 can easily do 7000 rpm and would probably max around 7200 rpm which gives me 4080 fpm on that engine. This video made me subscribe thanks for the info.
I was just watching you talk about this subject in your new How To Pick A Cam video and it seems like it would make more sense to pick a piston speed and calculate for RPM. With a desired piston speed of 4000 and a stroke of 3.5 inches it would look like this 4000 X 6 = 24,000 ÷ 3.5 = 6,857 Then you just round down to the nearest hundred just for safety, 6800 is the right RPM. If I'm wrong let me know.
Great video. Not sure where the 4000 fpm number comes from, but definitely gave me something to consider. I used your equation in reverse to determine the theoretical redline on my Buick 455: ((4000 fpm) x (6 factor)) / (engine stroke) = (theoretical redline) (4000x6)/3.9=6,150 rpm. 👍
yeah I wouldn't run a 455 to 6,150 for very long though, the oil system just won't doesn't support prolonged revs. The Buick, Olds and Caddy engines suffer from pumping oil to the top end and not draining back to the pan resulting in bearings not receiving adequate oil. This can all be "fixed" but be careful in a stock application.
great video, came at a really good time, I am putting my 283 short block together soon. really want it for a RPM grabber for no good reason at all, just to have fun with... I am deciding on heads, I have flat top forged pistons, stock rods with ARP bolts in them. Q: stock heads fully ported( non humps) or newer style "vortec" head (305ci) or something else. any advice would be awesome, thanks!
I have video of the 283 with vortec 350 heads and I loved it but they ended up being cracked and that is why I am redoing it. just looking professional advice as I am about 35 years old and this is the first 283 I have messed with. thanks
So with the factory nodular crank, properly conditioned rods, forged pistons (.030"), good oil circulation and quality bearings and fasteners my 350 Oldsmobile should be Ok at 6000 RPM? The original (#6) heads are filled with bigger valves and with the bowls and porting work, which included removing the EGR bumps from the exhaust passages they flow just over 230 CFM @.500" on the intake side and around 200 CFM for the exhaust. Compression ratio is near 10.6:1. The cam is hydraulic flat tappet design. I am using the manufacturers recommended springs. They rate the power curve between 2000 and 6000 RPM for the cam grind. The intake is also rated between 1500 and 6500 RPM. I will be running 1 3/4" primary headers with 3" collectors then reduced into an 2 1/2" exhaust pipe with an X cross-over and full mufflers. DO you think if I keep it cool, have plenty of spark and feed her with a 770 CFM carb, It will still be safe to 6000 RPM? This is a street engine that may never be raced but I like a little extra rumble for character.
It sounds like your on the right track 6000 should be fine with those components 230 is decant flow for a factory casting that's about what the vortec sbc head flows and they perform very well on the street keep your piston speed at 3900 or below and you will be fine I think the 350 olds has around 3.500 stroke that puts you a 3500 FPM at 6000 watch your total timing use good fuel and bullet proof the cooling system should make gobbs of power Olds engines are very strong runners sounds like your having allot of fun Good luck
3.385" stroke for all small block Olds. The 350 started with 4.057" bore (now 4.087 of course). This is my first Oldsmobile build. I have done a few Chevy and Ford engines in the past. A lot of research went in. Like most things, there are a lot of different opinions on what works and what doesn't. It seems the #6 factory heads (1970) had the greater potential. So exploited that. I had been watching a lot dyno videos and I liked they way most of the Oldsmobile small blocks seem to build more consistent torque over a much broader RPM range than a comparable Chevy, but really I chose it because the car is an Oldsmobile (1985 Cutlass Supreme) and every one builds Chevy. If easy big power was all I wanted I probably would have found an LS engine. The cooling system is in the works. I know the compression ratio is a little high for street use so I will be using a ram-air set up and most likely an E85/ Gasoline mix. That seems to work for everyone else I know running high compression or high boost. They mix at the pump for street driving and buy race fuel at the track, but I am not going to the track. I just want that old school V8 feeling. Some day I will post videos. Thank you for your input and for sharing your education.
It's really a function of thermodynamics and friction...with the mechanical design being adapted to address the dynamic metallurgical structural weaknesses (a multi degreed Aerospace Engineer who works for a large American defense contractor.
I was getting 7 grand shifts out of my 68 327 Camaro until the drive shaft came through the floor board. And that was with points not electronic ign. A 4speed trans and 3:08 rear.
I don't understand why the piston travels faster if it has a longer stroke. To me it appears, according to your formula, that the speed(rpm) is remaining constant but the distance covered is increasing with stroke. The stroker is not traveling faster but moving further therefore momentum plays a bigger role. What am I missing?
Great explaination. Just hope you can tackle cam design for the other unemformed some time, especially the part on advertised duration (SAE measures @ .004, where Crane Cams measures their cams), Comp Cams ( at .006s), and others and how this affects actual cam duration and how this affects power.
Could you add what would help turn more rpm I build alot of dirt track engines in many classes alot of people need to understand what helps engines live at rpm , great video thank you .
I got a small block Chevy 327 , it has 12:1 forged pistons , steel Vette crank in a 4 bolt main block , It cranks 11,000rpm before the valves start to float
Due to rod geometry, the fastest piston speed is usually in the top 1/3 of the cylinder. In the center of the cylinder, the piston is starting to decelerate as the crank comes the 90 degree point, actually starts decelerating at about 60 to 80 degrees, and decelerates the most as the journal starts to swing back in the bottom half of the stroke, stopping again at BDC. Also, a short rod engines like the Ford 302W or Chev 400 small block have faster acceleration away from TDC, once again due to rod geometry, than a longer rod engine, like the Ford Boss 302 or Chev 350, which can cause a piston to pull apart easier at the same RPM.
That depends on rod/stroke ratio Most engines peak out at dead middle of the stroke Engine with short rods and long stroke will have 2 peak pistons speeds near 1/3 down and 2/3, but actually slow down some in the middle of the stroke. that's because rod angularity accelerates the piston against the cylinder wall, but this increases runner air velocity and can be used to increase volumetric efficiency Peak piston speed at redline for a 5.0L is 82.5, while LS3 is around 72mph
The rod/stroke ratio will dictate piston accelerations and decelerations, but geometry dictates speeds in any part of the cylinder. Short rod will have quicker acceleration/deceleration, but, as the crankpin nears the halfway (90 degree) of stroke, piston speed starts to decrease as the rod angle change slows, no matter what rod length, usually around roughly the 30 - 45 degree range of stroke which has the piston in the top 1/3 of the cylinder. A shorter rod may have the piston farther down the cylinder, but not usually at 1/2. The difference between short rod, such as a 302 Windsor and longer rod, like a Boss 302, also dictates the cam requirements of an engine. Shorter rod engines like fast valve opening and higher lift at TDC to make use of the quicker piston acceleration away from TDC. Also makes use of larger carbs, valves and ports to allow less restriction to airflow acceleration as the piston moves from TDC. An easy way to study rod length on piston movement is to make a 2-d cardboard replica of a crank and cylinder. Make a circle to show the crankpin rotation and use a ruler for the rod. Pick points around the crank stroke and then match the ruler to the centre of the cylinder at different lengths from the same point in the stroke. You will see how the piston is higher or lower in the cylinder as rod length changes. The fun thing with this is that you can use rod to stroke ratios that would be impossible in real life to exaggerate the results and get a very good indication of how they affect each other.
Hi, In AU. The last ford 5ltr w XR 8 had the GTP aswell. Would you agree for the street. Leave the happy stroke, but bore to 40" - 60" 220, 512.110 grind, and change nothing else, i think would sound better, good horsepower, std dwell for the injection and timming curve, good on fuel. Has anyone compare this insead of some stroke increase . Mike
hi great vid , does this same rule apply to the 366 gm big block truck engine ? or are all stock engines built to a certain standard or envelope that all stock engine engineering fall into ? .the reason i ask is because the 366 has extra heavy 4 ring pistons and planing to build one for towing , redline under 5500 rpm , Thanks
1968 Corvette 327/350hp, rebuilt double hump heads (new hard seats, new springs, new 1.94"/1.50" valves), flat-top pistons, Edelbrock 2101 Performer, Holley 600CFM vacuum secondary, 488 lift comp cam, headers have 1.5" tubes & 3.0" collector, 4.030" bore/3.25" stroke, and approx 9.57:1 compression ratio -------- Let's do the math...3.25 stroke x 6000 RPM = 19,500 / 6 = 3250 ft/min....do you think 6000 RPM makes sense and is a safe number? By the way, this was a 327/300hp from the factory with a 5300 RPM redline. Thanks!
@myvintageiron7512 You do a great job explaining how things work! Your videos are the best. I wish Google would link to more of your info in the search results.
what would be the flow numbers of a set of heads that had the same size valves "175 intake 175" exhaust valves always see bigger intake valve but exhaust is always smaller ???
That is why I love the 302 Engines because they are Short Stroke Wide Bore and you can wrap them out even stock I nailed 5500RPM in my Bronco few times and it felt smooth at that high RPM Also Short Stroke wider bore engine have much better Throttle response in my Opinion.
Im planning on building a 355 chevy small block, got my 350 LT-1 in my 94 Caprice 9C1. What would be a rod to use with the hyper pistons and what kind of crank should i use? Im planning on using GM HotCam LT-4 cam and roller lifters. I am planning on getting heads ported and polished and port matched with intake manifold and Hooker street force headers. Already have headers and true duals on the car and Flowmaster muffs 50 series 3 chamber muffs, 2 and half inch exhaust. Will add 52mm throttle body and PCM modified chip. What kind of HP do you think I will get out of her? I know its 300hp stock.
So bore and stroke is 3.70 x 3.28 in. On my tacoma. So it would be 3.280x7000/6 ? If so I got 3,826 FPM. I hope I did this correct 🙏 this would be awesome. Thank you.
please respond to my question. i have a 1992 toyota celica gts 4cyl 2.2l manual says 135 @5400rpm peek hp and toque 145 @4400rpm is it safe to winds it out at those rpms every day ?
What I heard besides the piston speed (mine at 7k is 4567.5) is that rod ratio is a big factor for cylinder filling & exhaust depending on induction. Is 1.75 r.r perfect or as close for maximizing all the induction?
Im 53 and been a mechanic most of my life. I`ve learned something new again.
Same here.
Just an outstanding series if videos.
63 : physically retired, THE day you do not learn something is a wasted day. MY personal motto that I live by .
really?
red line has different things, not only piston speed.
@Randy Wiesendanger until you learn that the word "cannot" and "can't" are not actually words at all.
@@jamessmith489 I have wasted many days as a trucker.
This really only explains the piston speed limit, though. In most cases, the actual limiting factor is valve float. For the bottom end, the limiting factor is ring flutter. If your piston changes direction too rapidly or your rings are too heavy, they lose their ability to conduct heat because they lose contact. They overheat and swell, which reduces ring gap. Once your gap hits zero, you seize and break stuff. Lighter rings and wider gaps can help you exceed the conventional 4k fpm rule.
For the top end, the reciprocating mass of the valvetrain, aggressiveness of the cam profile, and strength of the valvespring determine the float RPM. This will usually hit before the bottom end RPM limit in a SBC because lifters and pushrods are so heavy.
Thank you for this!
I am 62,,,been master tech most of my life. But I have to say I really enjoy ur videos. I'm thinking I learn something every time I watch one. I thought I knew everything about RAT motors cylinder heads. But I learned something from that video as well. Thanks,
Glad to hear it
I saw this video about a month ago. Great information. Thanks!
HOWEVER.....I thought, "Where did the magical divisor of "6" come from and what is its unit of measure"? To go from inches to feet, you MUST divide by 12 (12" in a foot) not; 6.
Then, it hit me last night. "Revolutions per minute". A revolution is a full cycle, both up and down of the piston.
So....you really must add the stroke up to the stroke down. For the 302, it's 3"+3"= 6". Then, multiply by 7,000 RPM to get 42,000 inches of travel per minute. Now, convert from inches to feet using the divisor of 12. You get 3,500 Feet per Minute....not Inches per Minute.
Yes, it's the same answer but, that's the correct way, in my humble opinion, to follow the units of measure.
He used 6 (half of a foot) because he only used half the cycle (the up stroke).
Now, why is 4,000 FPM the magical number? It seems to be factual but, why?
I can't see my 1973 302 turning 7,000 RPM.
Awesome, thank you. I've asked all over the place for a max RPM on my Ford 400 that I'm building, I went with my gut of 5900 max with a stock bottom end (4" stroke) and hypereutectic pistons. With this calculation, 6000rpm is exactly 4000fpm.
Subscribed, thank you.
Accelerate until catastrophic failure, then reduce RPMs by 11.7%.
Hey what do you know, it works!!! 🤔🤔🤔
Absaalookemensch, I always built my engines with a rotating assembly that wasn’t the limiting factor. I used valve float as the redline.
I did it, but I'm struggling to only reduce engine speed by 11.7 percent. Suggestions?
Joe cook, Joe, what engine are we talks about? How many cylinders? Valve train design? Overhead valve overm? Has the rotating assembly been balanced to +/- 1 gram? If you have an oversquare engine you can achieve a higher piston speed before catastrophic failure. This will also depend on if your using cast or forged crankshaft.
@@arttafil6792 haha it was just a joke man just having a laugh
I really like your videos; A++. They are packed full of information. I hate going to watch a video for information, and the guy takes up half the video watching him eat breakfast, and then going to visit his Uncle Bob.
Very good info. I've been asked many times, How do you know if you've over revved an engine. My definition is, localized pains in and around the left hip pocket and the realization that your engine will now fit loosly in a 5 gallon bucket. lol!
Lmao!
When the Gremlins start playing death metal in the oil pan. You will know.
Didn’t Richard Petty say: we had an oil pan failure at 6800rpm
That was the best most informative video I've seen on RUclips. Thank you and keep doing what you're going
Interesting technical advice, after tinkering on engines all my life I always wondered how engine manufacturer's calibrated an engine's redline.
You just earned yourself a subscriber. Awesome video man. There is a lot of information in this video, but it's not spoken like it's being read from a book. It's broken down into "laymens" terms and it allows almost anyone to understand it. Awesome video.
Believe it or not there is a rule of the thumb that requires almost no calculation at all. Some extrapolation is required as the rule of the thumb part only works for 6000rpm.
So all one has to do is know the stroke length in decimal inches, add a zero to the end and voila!
3.00" stroke = 3000 fpm MPS @ 6000rpm
3.50" stroke = 3500 fpm MPS @ 6000rpm
3.75" stroke = 3750 fpm MPS @ 6000rpm
I am confident the 4000fpm could be easily exceeded in small motors with low reciprocating mass. An example, for the road going Honda 250cc 4 cylinder Learner motorcycle - the CBR250RR has a 1.33" stroke (33.8mm) and can turn 20 000+rpms. So 1330fpm @ 6000rpm will equal 1330X3 which is 3990 fpm MPS @ 18000rpm (1330x3 as there are three sixes in eighteen - puts you in the ballpark of 20 000rpm. This is the extrapolation bit)
I told a mechanical engineer of this and he scoffed. I taunted him to run the numbers which he did there and then and looked up in puzzlement at me and announced "You're absolutely correct."
Your equation is ideal for knowing the exact mean piston speed mine is just a simple rule of the thumb one could apply to say talking to a customer over the phone.
Great informative vid BTW :)
This is actually pretty good! I'll remember this forever, without even trying. Thanks for sharing it👍
Another method which is very simple. 24000 / stroke = redline. (This works if you are aiming for a 4000 feet per minute max)
You should not use the term "rule of thumb" if you knew the history behind that "saying" I dont think you would say it. I do not.
@@DavidStirm I wish someone would use the rule of thumb on you and beat that politically correct nonsense out of you...
Thank you Tom Hanks
lol
HA!
bro, I wasn't ready for that comment 😂
Vicente Bianchini 😂😂😂😂
Vicente Bianchini where you going Jenny😂
This video and the one covering camshaft selection are priceless additions to my future engine build. I was given an LS1 from an '98 Camaro and want it to both make good TQ/HP numbers but also give me half decent mileage. I know you can't have both high peformance and high mileage, but there is a sweet spot one can achieve w/ careful planning. Its going to be a challenge w/ the lack of bore-ability of the block, but I should easily be able to hit the milestone of one HP per C.I. w/ a proper balance and assembly. My goals are maximum torque while maintaining emissions compliance, as its my daily driver.
Im slowly working through your videos,and i damn well wish i could actually buy you a few beers,because they are fantastic! I live in the UK,& us chevy lovers are few & far between! Im just considering putting a Gen 5 454 into my 1980 Z 28 Camaro.Thanks again for such great info & videos!
Very good video.....good explanations. I used a 350 Chevy for brackets back in the day with a built motor...good rods, crank, forged pistons, ported heads, bigger headers, good collectors with open exhaust, 5:56 gears, etc. Depending on track conditions I used Victor or aluminum Corvette/Edelbrock 180 degree intake..... If I recall I used a 30-30 Duntov with solids.....it was a good cam because I could open or close the clearance to vary how "big" the cam would be. I would run about 7000 rpm and go thru the eyes at 7200. It held together forever but I watched the tach like a hawk. The car was not licensed for the street. I guess I could have been more radical but this was before all the aluminum heads, etc came into being. I think in those days we understood more about how enginces, etc worked because we HAD to figure it out for ourselves with the machinist. Today, guys can open their wallets with little knowledge and end up with a pretty good engine.
This might give you an idea of how old I am. When I was young I had a Nova that I played with. I liked the 283 over the 327, with low fives in the rear end I would run out of motor just before the traps. The 327's would not survive this treatment a couple of dozen times. Here's the age part, before all these fancy head I had double humps on the 283's. After each run I would pull the pushrods and roll them to see which ones were bent and hammer the studs back in the head from the rocker arms pushing them out. The 283's never reached the speed on the piston to destroy its self or throw the rod and the extra weigh from the 327's piston would grenade the rods. Your explanations over the last few weeks is the best example of why this happened. I really like what you are doing for the, shall we say less experienced persons like my self. Keep up the good work, and yes I grumbled to about the machine work. But the better it is engineered the longer it lives. BEST OF LUCK FROM SOUTH FLORIDA...
Aaaa yes I remember those days my first drag car was also a nova I built a 307 bored it .060 over and ran camel hump heads with a 310 duration Isky cam hooker headers and a big Holly carb I never had good power brakes because of the cam no vacuum booster! I know it sounds silly to build something like that now but at the time it was all I had and it ran pretty good for what it was I ran mid 14's all night long and never hurt the engine my gear was a 456 and I would hit 6200 RPM at the traps I've since had much faster cars and much more powerful engines but that 307 nova is somehow still my favorite car there was just something about Friday night drags back then lots of garage built Ford's and Chevy's, Pretty girls, and not an import within 50 miles those were the days thanks for this post you just made my day!
Myvintageiron7512 Wow that seems like the hard way to run 14's. My Nova has a rebuilt 350 (actually a 355) with 882 heads, dual plane aluminum intake, quadrajet, and a .435/.435 270 duration performance "RV" style camshaft that runs 14s with the factory 2.73 gears in it. Those gears also allow me to take it on the freeway unlike those 4.56s. Also runs in -10*F and +100*F ambient temps without issue. Oh and I still have plenty of vacuum for stop and go traffic ;)
well you see back then I didn't really know what I was doing and building a 307 was proof of that the thing is I was 17 and I honestly think I had more fun with that car than any other car I've owned or built even though I moved on to much bigger engines and serious drag race cars The Nova was my first and there is just something about the first time.
Myvintageiron7512 The best way to learn is through experience! I also here you about the first time. I made the mistake of just bolting on a single plane intake manifold and mechanical secondary 4 barrel carb on the inline 6 in my first car. It was impossible to tune. Sometimes it would shoot off like a rocket but often it would bog, never could get it to run quite right. But when it did go my little four door could blow the doors off 5.0 mustangs and most older fbodys through the 1/8mi.
I've learned from my mistakes and that's why my Nova has a dual plane (Weiand) intake and a vacuum secondary carb (quadrajet). Ok, so there was a lot of engine building theory studying going on between then and now too.
Keep up the great work on this channel! You've been verifying I built the motor up in my Nova correctly. I'm looking forward to hearing this stroker motor run.
@@Myvintageiron7512 Yep, I was drag racing at 20 years old in my own car. I left home at 15, got myself a job at the local garage and never looked back. It was 40 years of automotive. I'm still mad at myself for not building a serious Nova.
thanks to reducing equations we can simplify (r*s)/6=4000 for the purpose of finding a target redline speed into 24000/s=rpm so simply divide 24000 by your stroke in inches to get the exact redline rpm.
Ariel Lezen I have 72.0mm stroke and I go to 7000 rpm can you calculate my engine redline
Exact stroke for max rpm of 7000 is 3.4285. What's cool is I just got my hands on an engine only made for 4 years 5 if you want to get technical. The stroke on this 383 is 3.380. So I have 0.048 to work with. Gets me thinking about the engineers and what they were really after. How about something that can be mass produced for intended use but, with a little modern (modern being used broadly, modern is just the time) technology for final touch up work. Can just sit happy right where a street RPM band engine should be for a V-8.
The issue is most production V8's are cammed/intaked to make power between 2-5k, after that they fall flat. If you change an engine to make peak power 5-8k customers would think its too sluggish or too much power pickup in the top range making it dangerous for inexperienced drivers. Its a tradeoff they had to choose reliability and fuel consumption rather then power
Ariel Lezen So since the tach is driven by the cam, every cam rotation the distributor tells the tach to double the amount of revoltions because the crank is 2x the speed of the cam ?
Great info that is data based. This equation takes the guess work out of what people assume is safe. Great articulation and explanation. Great job on the video. Thanks for taking time to offer this research.
Until I had watched your video I had naively assumed that the connecting rod length was almost entirely a side load issue.
I had not realised that it also had an effect on dwell time..
you are right of course. It is a shame that people don't always pay proper attention, I cannot fault the information you provide.
I think that rather than disputing the facts people should perhaps watch the video a second time, well done on a well put together video.
Been around cars a long time and never heard of this formula before. Building a BBC and wondered about max RPM. Thanks for the info.
I learned a lot just from this video, very well explained
You're missing the reason for the longer rod!! You understand the higher RPM and stroke reasoning, but the advantage of the longer rod is entirely geometric! A greater advantage is achieved with a longer and more angular focus on the crank increasing the leverage and advantage!
He didn't miss it. All he was talking about was the components and if they can take the speed you are wanting to spin the engine to. The advantage means dick if the internals can't take the forces and become separate pieces.
Good day I am looking forward to rebuilding my 4.0l Jeep motor this summer. Following the formula to figure out my RPM I should be able to build my motor to match the drive train. Thanks for the information and the simple way of explaining things.
what ?? are you afraid your engine reach 11.000» kekeke
try it first, then try to control it...
When I was younger my dad built a 351W with Cleveland heads, and he swapped over to a solid cam, adjustable valvetrain setup with a lumpy cam. He always told me that a 351 could pull 7000, but I really wasn't sure how that was possible since the 4 cyl in our Focus barely did 7000. Now that I'm following suit and getting into cars, and that I have more knowledge, it's easy to see how to squeeze revs out of an engine. As always, well explained video.
+Ryan Eyster A 351W will turn 7000 it is feesable to go above the piston speeds I have laid out race engines do it all the time you just need stronger internal parts and a much better balance job 4000 FPM is a good safe max piston speed for a stock engine
The Cleveland will do 7000 more reliably because of the smaller crank journals. One of the other things that affects the rev potential of an engine is its ability to reliably supply oil to the journals, and larger journals require a better oiling system to supply enough volume due to the cast-off created by higher surface speeds.
You mean Windsor don't you? Cleveland is ordinary by design.
ThePaulv12, no, the Windsor is a wedge head engine, like the 302, that was never as popular for performance as the Cleveland. The Cleveland is a canted valve head, like the big block Chevs. It also has a shorter deck height and smaller main bearing diameter than a Windsor. A 2bbl Cleveland had heads that were more than adequate for most street and racing, but, the 4bbl heads had huge ports that are said to outflow a 427 rectangular port Chevy. These were the same heads used on the Boss 302 and had a very high rev capability due to the flow.
Best explanation I've heard on the subject, great teacher.
Thanks a lot, things are always more complicated then they appear. Keep these videos coming.
I've seen dirt track racers consistently run 350 Chevy's with stock bottom ends to 7000 RPM but on a few drag race cars I've always played it safe to 6500. Had a 396 once that I would turn to 6000 RPM. But I'm a cautious guy. Great video and thanks for explaining the numbers.
my 409 and 348 both topped out at 4300 RPM. 327-375hp slightly built about eight. But no matter what an engine was rated for I usually drove by ear and feel. Great video's, thanks.
Again thank you. Your totally right if your going to beef up the bottom end as to run high RPM it's wise to put money into valves, springs, Cam etc.
4000/(stroke/6)=max RPM. Gives a definite safe answer that results in exactly 4000 FPM of the piston. Thanks for the info!
Equation works! My mercury v8 outboard has a stroke of 3.4in, so that means theoretical redline of 7000. Factiry redline is 6200, but the "race" version is 6500.
Terrific videos. Please keep up the good work. I learn every time I watch.
With this math my Olds 403 could rev to 7,000 rpm. Unfortunately the weak windowed block can handle that. Kinda wish I went for the full monte J&S Halo girdle (did install the 4 main girdle) I'll keep it to 5500 and less and hopefully I don't blow the thing to bits. The 403 bore stroke ratio theoretically is great for a high revving engine, but the block strength holds it back.
Strong internals go a long way here. 4340 crank and fully forged pistons and rods @ 4.25 inch stroke hasn't cared about 7500 rpm in my little hotrod...Yet... Pettis performance builds 598 Chevy (race motors) with 4.5inch stroke that make peak power at 9k. Very informative video!
Hmm, with this formula, the Olds 350 and 403 appear to have a slight advantage over their Chevy cousins with the same cid. The 350 rocket is a highly under estimated engine. Early 350 rockets can be bored to the 4.125 bore the 425 and 455 share, but have a 3.385 stroke, They can also use the big block heads as a upgrade. Even with windowed mains, the 403 can produce some insane numbers.
Thank you for this video. I've been wondering about all of this for years.
Question: To what degree does the width/resistance of piston rings and the weight of the pistons (in after market situations) play a role?
Excellent video. Makes this pretty understandable for us dummies.
Thanks, this was a great explanation on how to find an engines recommended redline and performance capabilities. As a side note what is the stroke length of a 5.3L LS engine or would a 4.8L LS engine possibly be a better option? I would like to use a M122 GT500 Roots style supercharger and possibly even use a turbocharger as well.
R.P.M's, i knows MANY mechanics/technicians use plural on minute. I have 2-96 Roadmasters with the LT1 cast iron head, I have no idea of the casting numbers but 2000 R.P.M's with the rowing package gets me 80 MPH all day. I bought one of those tuners to tweak dis n dat and raised the governor from 108 to lotz more and put higher speed rated tires on one of them and now I've been to 3500 R.P.M'$ which is/was north of 130 M.P.H'$ on highway 99. Built a few engines and enjoyed the few videos of yours I've watched.
Gene from the left coast near the state Crapitol
What does it mean when a connecting rod flies out of the bottom of the oil pan? Really curious if its going to affect my fuel economy.
351cleavland usually the failure of the end cap or connecting rod bolts ... i.e. ..flies out .. other sources of failures can contribute too .. lack of oil psi to the bearings , cause the bearing to fail .. excessive clearance leads to the "knocking " then excessive heat , gaulling , seizure , boom ... the rod is the last to get oil ..
put the rod back in and jb weld it back in place, should be fine just use plenty of JB
...change your oil more
randysengine service Sure, I did that and a week later a piston flies out the engine compartment into the cabin and up and out through the sunroof! I am 50% sure its not going to bre covered by warranty!
Your fuel economy will improve because the car becomes lighter due to less rotating mass in the engine ;)
Great info on RPM. Thanks for putting these videos together.
Thank you for your Chevy 350 Video Series. These videos have helped me improving my technical understanding of the 350.
Im saving up for my first engine Rebuild or Engine Build right now.
....Best Case scenario....
I'd LIKE to see 600 hp/ 550 Torque out of my current 350. either in the 383ci or 400 ci. but since I still need to iron out other details on the truck. I'm probably just going to do a HO 350 rebuild for now. so I can drive it while I get the other details fixed as I go.
I'm considering buying a built crate Engine or sourcing a LS Engine later.
the problem I have with the LS Option is.
all the little stuff im going to need in order to make the LS work in my 94 S10.
Wiring. Engine Mounts. power train. Computers. transmission linkage. cooling systems.
yada Yada yada.
I have a 92 S10 myself. As well as a 1970 350/300 4bolt along with a good 350TH to use if I wanted. Same problem as you. The LS option is for sure going to require extensive wiring and what the heck, the speed it is going to generate might as well figure in a suspension as well. Lord knows the flimsy shocks that you get for the S10's isn't going to handle the corner speeds... I'd like to do anything/everything to the 350 and sit it in it, but hate to think that it will be just a putt putt truck...
@LORDdeath Gaming You're making more out it than necessary for an LS swap. The wiring is a simple affair that you just lay on top of the engine, once installed, and start making connnections - it falls together like falling dominoes. I was intimidated by the prospect as well, but it went quite smoothly, once I hunckered down and started the process. As for your plans for your SBC, just remember speed costs money, so get rready to spend a pretty penny for an engine w/ those specs. Just sayin' those are big block numbers. Best of luck.
Reliability/durability of the crank and bearings are what limits rpm, right? They the failing components of high rpms, right? Can you increase rpm and/or add stability/reliability to the exicting redline by using a higher viscosity oil or some kind of racing oil?
Very informative especially for someone who is not a mechanic, but I have a question- If I have a neo vvl St 20 will installing a vvl controller and setting it before 5000 rpm harm the engine? Thanks
Great video, I have a 2003 Toyota Matrix XRS which has a 2ZZ-GE engine that red-lines at 8200 RPM with a stroke of 3.35". By your formula my pistons are traveling at ~4575 FPM. But I guess that is what you do when you are a large corporation and reuse and engine that you put in a Lotus Elise/Exige.
Forged steel crankshaft. Refined rods and pistons. Much better castings than the engine community he is referring to.
Type of alloy used also plays a part.as we all know hypoutechtic pistons love to handgrenade if pushed over max speed
Not to mention, bearing surface speed with longer stroke requiring a better oil delivery to cool the bearing surface. With oil temperature being more critical to making power, the window narrows significantly. The old rule of 10 psi per 1000 RPM may not be sufficient.
I have a friend randy that built a Chevy small block back in the late 80s that saw the far side of 8700 rpms and that thing was a beast, it never came apart , it was in a 69 Camaro, I saw that car beat built 600 hp big blocks , one guy he raced and beat said i heard the horse power screaming out of your grill when you passed me
Great job explaining this...i see things much clearer,,thanks
Glad it was helpful!
What about pin offset and reverse offset ? Racing pistons are usually centered or reverse offset and always Clack making a distinct sound.
Great video. You explained the concepts perfectly.
I really love your videos man. Keep it up!!
Where does the "divide by 6" part come from?
Here is an interesting fact you may not know. The piston moves faster closing in on and moving away from the top of the stroke versus closing in on and moving away from the bottom of the stroke. The reason why is because of rod angle effectively acting like it's growing the rod in length as it approaches TDC and in effect shortening in length as it draws away past TDC. The distance between crank throw and wrist pin varies with the angle of the rod.
Growing in length while approaching BDC, bottom dead center actually slows piston speed down. It may be hard to fathom but the net effect is that there is more dwell time at the bottom for cylinder filling and less dwell time at the top to take advantage of chamber pressure. Learned this phenomenon at the tender age of 70.
Would be cool if you did a video on the effect the connecting rod length to stroke ratio has on the hp and torque of an engine.
I've always wanted to build a Bug engine with a 1300 crank and the biggest bore pistons the bore centers would support and then have the cylinders long enough to support 2.3 x stroke ratio. Billet heads with the biggest valves that would fit without shrouding in the bores, and as close to a 14:1 compression ratio with closed chambers and D cup pistons. The camshaft would be tuned to the dwell time of the pistons at the top of the bore. The next thing would be a single plane pyramid intake with a tuned plenum and runners along with a Holley 660 center squirter carb.
I know the Euro guys like the weber carbs for throttle response, but a single plane intake with a combined tuned exhaust makes more power overall.... Anyway, would be fun to build such an engine.
and then your valves melt because tetraethyl lead 3 is bad for the environment unless you use 109 octane leaded av-gas.
+Ray Main You're even getting me excited. Remember high compression = pumping loss. There have actually been a number of very high compression production engines over the years and after the first run they were always backed down to around a still high 11:1.
Another thing, by my way of thinking, very high compression is only worthwhile (on the street) if the ignition timing is
how do you determine what the piston speed should be for a engine? example. hp rods and a low rpm high torque cam. over a stock cam and rods. or a high rpm cam and rods.
Now that was informative thanx bud.
Ive got a 355
Id say a lil bit more than moderately built .i twisted it to 7500 and 3 of my harland sharps started clacking pulled covers off and had 3 backed off to abot .050 .supposed to be .021 wp heads,1.555 springs,doubles with dampers. Cam .600 in
.625ex..rockers actuall hit stud girdles.ALMOST A CATASTROPHIC.
What is the “6” referencing?
Great video. Thanks for taking the time.
just an educated guess but the reason why you use 6 instead of 12 to go from inches to feet per minute is because the piston travels the length of the stroke twice for every revolution . so really what you are doing is ( stroke/12 ) x 2 which is the same thing as dividing it by 6
I am spinning a 4.6" stroke at 7400 RPM.
But as he says, much must be done to be strong enough to do it. Billet crank, rods and main caps to start. This is in a one off tall-deck LS race block. (LS blocks have fully girdled main caps unlike SBC, so that helps too)
But that give you an idea of where things can be taken if you want it bad enough.
and 7.000 is a lot??? kekek you should have seen 11.000 rpm
learn something new every day. Love it!
Sort of off subject but could you explain briefly the designation of Chevy engines. I see references to LT1, LS, Gen1, Gen2. Pretty confusi g when looking for parts.
Thanks. I enjoy watching your videos!
What about the LS1 Chevy engines. There built with 6 bolt main caps plus rev to the moon and back. Rev Limit from factory kicks in about 6200.
What I was hoping would be covered in this video was the effect of longer rods on the same stroke...I've seen a lot of guys build "long rod" engines, but are the gains worth the time and effort? I've also read that long rod motors make much better use of small valves and ports, but I haven't come across very many A-to-B comparisons.
Cool information my stroke is 3.6 so it seems as 6500 is the max safest rpm I can go on my engine which is 3900 fpm. And you said the longer stroke gives more torque which is interesting as I could tell my engine was a lot more torquey than my 3800 L36 powered car which according to this formula the L36 can easily do 7000 rpm and would probably max around 7200 rpm which gives me 4080 fpm on that engine.
This video made me subscribe thanks for the info.
Say we have a forged lower end, what would be a safe piston speed for that? Building a 334 stroker sbc for boost.
I was just watching you talk about this subject in your new How To Pick A Cam video and it seems like it would make more sense to pick a piston speed and calculate for RPM. With a desired piston speed of 4000 and a stroke of 3.5 inches it would look like this 4000 X 6 = 24,000 ÷ 3.5 = 6,857 Then you just round down to the nearest hundred just for safety, 6800 is the right RPM. If I'm wrong let me know.
That is exactly correct!
Great video. Not sure where the 4000 fpm number comes from, but definitely gave me something to consider.
I used your equation in reverse to determine the theoretical redline on my Buick 455:
((4000 fpm) x (6 factor)) / (engine stroke) = (theoretical redline)
(4000x6)/3.9=6,150 rpm. 👍
yeah I wouldn't run a 455 to 6,150 for very long though, the oil system just won't doesn't support prolonged revs. The Buick, Olds and Caddy engines suffer from pumping oil to the top end and not draining back to the pan resulting in bearings not receiving adequate oil. This can all be "fixed" but be careful in a stock application.
great video, came at a really good time, I am putting my 283 short block together soon. really want it for a RPM grabber for no good reason at all, just to have fun with... I am deciding on heads, I have flat top forged pistons, stock rods with ARP bolts in them. Q: stock heads fully ported( non humps) or newer style "vortec" head (305ci) or something else. any advice would be awesome, thanks!
I have video of the 283 with vortec 350 heads and I loved it but they ended up being cracked and that is why I am redoing it. just looking professional advice as I am about 35 years old and this is the first 283 I have messed with. thanks
So with the factory nodular crank, properly conditioned rods, forged pistons (.030"), good oil circulation and quality bearings and fasteners my 350 Oldsmobile should be Ok at 6000 RPM?
The original (#6) heads are filled with bigger valves and with the bowls and porting work, which included removing the EGR bumps from the exhaust passages they flow just over 230 CFM @.500" on the intake side and around 200 CFM for the exhaust. Compression ratio is near 10.6:1.
The cam is hydraulic flat tappet design. I am using the manufacturers recommended springs. They rate the power curve between 2000 and 6000 RPM for the cam grind.
The intake is also rated between 1500 and 6500 RPM. I will be running 1 3/4" primary headers with 3" collectors then reduced into an 2 1/2" exhaust pipe with an X cross-over and full mufflers.
DO you think if I keep it cool, have plenty of spark and feed her with a 770 CFM carb, It will still be safe to 6000 RPM?
This is a street engine that may never be raced but I like a little extra rumble for character.
It sounds like your on the right track 6000 should be fine with those components 230 is decant flow for a factory casting that's about what the vortec sbc head flows and they perform very well on the street keep your piston speed at 3900 or below and you will be fine I think the 350 olds has around 3.500 stroke that puts you a 3500 FPM at 6000 watch your total timing use good fuel and bullet proof the cooling system should make gobbs of power Olds engines are very strong runners sounds like your having allot of fun Good luck
3.385" stroke for all small block Olds. The 350 started with 4.057" bore (now 4.087 of course). This is my first Oldsmobile build. I have done a few Chevy and Ford engines in the past. A lot of research went in.
Like most things, there are a lot of different opinions on what works and what doesn't. It seems the #6 factory heads (1970) had the greater potential. So exploited that.
I had been watching a lot dyno videos and I liked they way most of the Oldsmobile small blocks seem to build more consistent torque over a much broader RPM range than a comparable Chevy, but really I chose it because the car is an Oldsmobile (1985 Cutlass Supreme) and every one builds Chevy.
If easy big power was all I wanted I probably would have found an LS engine.
The cooling system is in the works. I know the compression ratio is a little high for street use so I will be using a ram-air set up and most likely an E85/ Gasoline mix.
That seems to work for everyone else I know running high compression or high boost. They mix at the pump for street driving and buy race fuel at the track, but I am not going to the track. I just want that old school V8 feeling.
Some day I will post videos.
Thank you for your input and for sharing your education.
Well thought out it should work well
So basically if you have a bigger foot on the accelerator, the engine can rev harder?
It's really a function of thermodynamics and friction...with the mechanical design being adapted to address the dynamic metallurgical structural weaknesses (a multi degreed Aerospace Engineer who works for a large American defense contractor.
I was getting 7 grand shifts out of my 68 327 Camaro until the drive shaft came through the floor board. And that was with points not electronic ign. A 4speed trans and 3:08 rear.
I don't understand why the piston travels faster if it has a longer stroke. To me it appears, according to your formula, that the speed(rpm) is remaining constant but the distance covered is increasing with stroke. The stroker is not traveling faster but moving further therefore momentum plays a bigger role. What am I missing?
Great explaination. Just hope you can tackle cam design for the other unemformed some time, especially the part on advertised duration (SAE measures @ .004, where Crane Cams measures their cams), Comp Cams ( at .006s), and others and how this affects actual cam duration and how this affects power.
Does piston and rod mass/weight factor into this. I'd think this would be the case because "an object in motion tends to stay in motion".
Q. When building a mud truck engine. Do I want to build a short stroke high RPM engine or do I need a long stroke torque monster?
Long stroke
Could you add what would help turn more rpm I build alot of dirt track engines in many classes alot of people need to understand what helps engines live at rpm , great video thank you .
just trying to understand and learn here. what is the number 6 from when working the formula?
I got a small block Chevy 327 , it has 12:1 forged pistons , steel Vette crank in a 4 bolt main block ,
It cranks 11,000rpm before the valves start to float
Due to rod geometry, the fastest piston speed is usually in the top 1/3 of the cylinder. In the center of the cylinder, the piston is starting to decelerate as the crank comes the 90 degree point, actually starts decelerating at about 60 to 80 degrees, and decelerates the most as the journal starts to swing back in the bottom half of the stroke, stopping again at BDC. Also, a short rod engines like the Ford 302W or Chev 400 small block have faster acceleration away from TDC, once again due to rod geometry, than a longer rod engine, like the Ford Boss 302 or Chev 350, which can cause a piston to pull apart easier at the same RPM.
That depends on rod/stroke ratio
Most engines peak out at dead middle of the stroke
Engine with short rods and long stroke will have 2 peak pistons speeds near 1/3 down and 2/3, but actually slow down some in the middle of the stroke. that's because rod angularity accelerates the piston against the cylinder wall, but this increases runner air velocity and can be used to increase volumetric efficiency
Peak piston speed at redline for a 5.0L is 82.5, while LS3 is around 72mph
The rod/stroke ratio will dictate piston accelerations and decelerations, but geometry dictates speeds in any part of the cylinder. Short rod will have quicker acceleration/deceleration, but, as the crankpin nears the halfway (90 degree) of stroke, piston speed starts to decrease as the rod angle change slows, no matter what rod length, usually around roughly the 30 - 45 degree range of stroke which has the piston in the top 1/3 of the cylinder. A shorter rod may have the piston farther down the cylinder, but not usually at 1/2.
The difference between short rod, such as a 302 Windsor and longer rod, like a Boss 302, also dictates the cam requirements of an engine. Shorter rod engines like fast valve opening and higher lift at TDC to make use of the quicker piston acceleration away from TDC. Also makes use of larger carbs, valves and ports to allow less restriction to airflow acceleration as the piston moves from TDC.
An easy way to study rod length on piston movement is to make a 2-d cardboard replica of a crank and cylinder. Make a circle to show the crankpin rotation and use a ruler for the rod. Pick points around the crank stroke and then match the ruler to the centre of the cylinder at different lengths from the same point in the stroke. You will see how the piston is higher or lower in the cylinder as rod length changes. The fun thing with this is that you can use rod to stroke ratios that would be impossible in real life to exaggerate the results and get a very good indication of how they affect each other.
Hi, In AU. The last ford 5ltr w XR 8 had the GTP aswell. Would you agree for the street. Leave the happy stroke, but bore to 40" - 60" 220, 512.110 grind, and change nothing else, i think would sound better, good horsepower, std dwell for the injection and timming curve, good on fuel. Has anyone compare this insead of some stroke increase . Mike
Could you do a video on how to degree in a camshaft and the theory behind it?
hi great vid , does this same rule apply to the 366 gm big block truck engine ? or are all stock engines built to a certain standard or envelope that all stock engine engineering fall into ? .the reason i ask is because the 366 has extra heavy 4 ring pistons and planing to build one for towing , redline under 5500 rpm , Thanks
Do I need to factor in the length of the rod into the formula ? Or is the stroke the main number I need ? Thanks.
Stroke the connecting rod length equals piston speed for when that piston goes up to top dead center and back down length of the connected rod
1968 Corvette 327/350hp, rebuilt double hump heads (new hard seats, new springs, new 1.94"/1.50" valves), flat-top pistons, Edelbrock 2101 Performer, Holley 600CFM vacuum secondary, 488 lift comp cam, headers have 1.5" tubes & 3.0" collector, 4.030" bore/3.25" stroke, and approx 9.57:1 compression ratio --------
Let's do the math...3.25 stroke x 6000 RPM = 19,500 / 6 = 3250 ft/min....do you think 6000 RPM makes sense and is a safe number? By the way, this was a 327/300hp from the factory with a 5300 RPM redline. Thanks!
6000 is no problem for a 327
@@Myvintageiron7512 Thank you sir!
Where did you get the 4000 fpm figure from ?
@myvintageiron7512 You do a great job explaining how things work! Your videos are the best. I wish Google would link to more of your info in the search results.
what would be the flow numbers of a set of heads that had the same size valves "175 intake 175" exhaust valves always see bigger intake valve but exhaust is always smaller ???
That is why I love the 302 Engines because they are Short Stroke Wide Bore and you can wrap them out even stock I nailed 5500RPM in my Bronco few times and it felt smooth at that high RPM Also Short Stroke wider bore engine have much better Throttle response in my Opinion.
Where does ring flutter come into play? Is that ring material or more based on piston speed?
Your tutorials are very informative....
Glad you like them!
How much improvement can be made by balancing the components ?
Im planning on building a 355 chevy small block, got my 350 LT-1 in my 94 Caprice 9C1. What would be a rod to use with the hyper pistons and what kind of crank should i use? Im planning on using GM HotCam LT-4 cam and roller lifters. I am planning on getting heads ported and polished and port matched with intake manifold and Hooker street force headers. Already have headers and true duals on the car and Flowmaster muffs 50 series 3 chamber muffs, 2 and half inch exhaust. Will add 52mm throttle body and PCM modified chip. What kind of HP do you think I will get out of her? I know its 300hp stock.
Thats some good info. Got exactly what i needed
what is the number 6 for when dividing by 6? what is its significance?
So bore and stroke is 3.70 x 3.28 in. On my tacoma. So it would be 3.280x7000/6 ? If so I got 3,826 FPM. I hope I did this correct 🙏 this would be awesome. Thank you.
please respond to my question. i have a 1992 toyota celica gts 4cyl 2.2l manual says 135 @5400rpm peek hp and toque 145 @4400rpm is it safe to winds it out at those rpms every day ?
What I heard besides the piston speed (mine at 7k is 4567.5) is that rod ratio is a big factor for cylinder filling & exhaust depending on induction. Is 1.75 r.r perfect or as close for maximizing all the induction?