Basic Holley Carburetor Modifications for Blow Through
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- Опубликовано: 11 фев 2016
- Here is a overview of what I did to modified my Holley 4150 for Turbo or centrifugal supercharger application.
Note: Can not use a carburetor with vacuum secondaries
Hanger 18 Write up: www.hangar18fabrication.com/bl...
Carb hat O-Rings: www.superiorairflow.com/carb-h... 
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Part 1 of tuning this carb can be found here : ruclips.net/video/ng4KpBz2FQ0/видео.html
Glad to see people are still using my writeup over 15 years later.
Hangar18Fabrication hi will a 600 4150 converted to blow thru br good for a 5.3 with a 69mm
I just used it. Thanks
Michael Foist what all did you modify on yours ? I have never used elderbrocks because in my exspience they have a dead spot that is impossible to get out. But in terms of converting to blow through they song leak boost like I have heard so many holleys do.
@@bryanroupe8646 check yur accelerator pump Holly's are bad about that even when there new
Man that thing is a gift to the performance world!! We thank you for taking the time to share the knowledge!!!
Awesome thanks homie 👍🏼I don’t know why this information is so sacred. The blow through carb is the deal breaker for most budget builds such as myself.
Never seen that done with rubber hoses. Pretty cool to know that actually works. Might come in handy during an emergency.
i only got this setup running yesterday, not monitored fuel pressure yet but used an innovate LM1 wide band to set afr.
+Jim Thorpe Oh cool ,good luck,have you hit boost with it yet?
Great vid... thanks for taking the time to post .. Cheers !
Thanks for watching!
Drew Fetters Wonderful .. thanks
Nice video. 4 years later. I will be building a blow through setup for my 1980 Capri 2.3 Turbo RS.
Thank you!
great explanation of key points. I put a turbo from an izuzu diesel(heavy truck) on my 78 f150 with a 300 straight 6.. I'm going to use a 670 Street avenger so we'll see how it works.
+Matthew Keeney Thank you. That will be a cool truck, I thought about throwing a turbo from a Dodge Cummins or Power stroke, but could not find one for a decent price around me that would be the right size. Comment back or throw up a video of how the modifications go if you think about it!
Putting one on my 77 f150 how much boost u pushin
How did that work out
thanks for quick reply I think im goin stick with put it to intake BT that way while under boost if any pressure bypass the rings hopefully it pulls
Didnt think of that. Good luck with the build!
What do you mean?
Thats what i call smart! And i would consider you a professioal! For someone to figure out way to do this . Who the hell wants to spend over $600 for a supercharger carb when you can do it yourself with basicaly any carb. GENIUS!
Haha thank you, just trying to share what I know and what I learned from the Hanger 18 article www.hangar18fabrication.com/blowthru.html .
thanks for sharing your video anyways even if you learned the trick from someone else i woild of never of see this if it wasnt for your vid u posted i just think it great people are still enginering stuff and cutting the red tape so to speak. All these big parts companies just want you hard earned cash and make you think you have to buy thier products like theres no other way around it ya know?
Its not like they will say hey to save some money just modify you own carb and it will work just the same. Its one way to stick to the man!!!! lol
Just like they wont tell you dont need a supercharger intercooler just run a hose or modify it in some way from your A/C evaporator will work just as good if not better!!!!
Question you drilled a hole in the carburetor hoedown post so I'm assuming the post must be hollow to let the air get down inside of it to the valve at the bottom I've never seen a hollow post
did the little brass bushes work to seal your shafts you mean? that might be an easier fix than what i had in mind.
Lol thanks i have a 84 bmw 325e with a 302 and a 750 doble pump. Im going to fabricate a turbo sidtem for it
Sounds like it will be a fun ride!
Did you do the turbo? I just ordered a turbo kit for my '93 325is that I 5.0 swapped.
Great vid thanks
Thanks for you.
So if you have something like a Proform racing carb that didn't come with a choke/choke tower, has the power valves blocked off (racing application), the only things you really need to look at on the carb are cork floats and maybe vent tube extensions.
I would say yes. Sense you don't have a power valve your main and secondary jetting will be way different than with a power valve, and it may be tricky to tune due to that, but that just a assumption. I would read " www.hangar18fabrication.com/blowthru.html " for all of the little details and small things that can be done also.
nice job
Thanks!
nicely done mate, little tip depending on your power level, it happened to me was running in constant air fuels in higher boost with my blo thru had me stumped for a while. Mucking around jetting etc, then decided out of luck too pissoff single line from reg too carb went twin dash 6s, problem fixed went back in jetting still solid air fuels.they need good fuel supply there no different to na only 5 or so pound of fuel above boost.they need flow,
Cool tip,thanks for watching!
i only went into boost with a hard rev from idle up to about 3k, but no road test yet as i'm waiting for a pair of shafts from Mosa.
+Jim Thorpe The road test is where you will see most likely that you will need a boost ref reg, and a fuel pump.At idle and reving you wont see the need for pump or regulator ,when you hard rev you are really only using fuel in the carb bowls and not needing fuel from pump because it is not under load or under boost for a decent amount of time.
Out of curiosity, what size jets are you running? and what vacuum rating power valves? Very informative video, I'm about to build a blow through carburetor for my turbo small block and this definitely helped me get an understand of what I need to do.
+yamahondarider Primarys: 65 secondary's: 70 .I Don't remember what power valve im running,carb is at the shop and engine is torn down ( seen in video coming out tomorrow). Glad I could shed some light on some things,thanks for watching!
Drew Fetters Wow, thats good to hear. I was afraid I'd have to be running some monster jets. Right now I've got 69 primaries and I believe 74 or 76 secondaries. Naturally aspirated mild 350. I suppose I'll do the basic mods and see where I'm at before I jet it way fat. BTW, have you noticed any downsides to keeping the choke horn? I see most people cut it off.
I removed my choke horn after this video was made but have not taken car out sense then.It should let air move into the carb smoother because it does not get restricted in the >1 inch space between the top of the choke horn and hat.On a NA car I wouldn't expect a difference in hp ,but might see some gains in boosted application . So downside is that might lose a little hp ,but thats just my thought,no evidence to back it up.
Is it the weber 38 going to be the same principle? If i did the float mod and change some orings will it worked out for boost prep?
All Carbs are going to be alittle different, never messed with a Webber carb,should be same principle though.Google is your best friend when figuring out these things!
hey drew just did all your mods to my holley 500cfm one ? my pcv valve will now go to my intake pipe before the turbo correct seeing how the the carb will be under pressure instead of vacuum? building a 225 slant turbo
Correct. You could also hook it up to the back of the carb on the base plate IF you have a good pcv that will fully block off any boost trying to get through(back to the crank case) ,because you will not be under boost all the time so when you are under Vaccum it will pull crank case gasses in.
Some cars have the pcv routed before the air cleaner too though they have their own sponge filter.
whats the deal with the two wooden sticks on top of the metering blocks? do I need to install on my carb?
Its called a vent baffle or vent whistle .The vent baffle is used with the center-hung style fuel bowl. It extends the fuel bowl vent to near the wall of the fuel bowl and can effectively control fuel splash on the primary side when accelerating hard, or on the secondary side when braking hard.
Drew Fetters @ok thanks!
Did you modify the meering block any?
might be a crazy idea, but, i'm running a std hei gm dizzy, if i leave the vac line off and use it like a locked out dizzy, surely it just won't advance at higher rpm where the boost is coming in. what do you think?
+Jim Thorpe Ive thought the exact same thing,but when you are not in boost it will feel very slugish. the best way is disconnect vac line, rev engine up to about 3-4k where it stops advancing itself and set your timing for boost.then reconnect vac line .because when you are in boost anyways you will be at 0 vac so that timing will be setting is the timing you get at wide open throttle in boost, if that makes sence.
yeh kinda makes sense, i'll have a play around with it and let you know what happens.
BOOM!!!! 😂
Do you have to upsize jets if you run turbo pressure to fuel chambers.Ive read that turbo pressure forces more fuel through jets. I want to turbo my stock N/A 4cyl. I've read a lot of forums about turboing even considered a draw through method. Hoping to get answer.
I Would say yes, but the only real way to find out in your specific application is to just do it. Looking back if I had the space ( like a 4cly does) or was turboing a smaller size engine, I would have went draw through.
Nuisance Racing It is relatively small engine 1598ccm i can run a lot of boost because compresion is really small. I have a lot of space engine bay is really big. It doesnt need to be anything spectacular it's just for fun.
LuX The only thing you can do is research, which it seems like you've been doing alot of,and picking the best one (draw through or blow through) .
Hey man, where did you connect your Boost gage? I’ve got my AEM Tee’ed off of the BOV line coming from a 1/8” NPT hole on my carb spacer but can’t get a good reading
What's not good about the reading your getting? Mine is off of the vacuum tree on rear of intake manifold. Carb spacer should be a good source for it though.I have sence switched over to EFI fuel injection, in some more recent videos.
I think I was too conservative with the settings on the boost controller. I went from 30% duty to 50% duty cycle and was finally able to build some boost.
Hey man I'm having an issue with my carb being super rich. I done all these same modifications and at first it was decent but when I gave it gas it rich misfired like in your other video of you driving but as soon as I jetted down it seemed to have go ten times worse. Idk what to do man please help
do you have any vent tube extensions on the carb?
@@NuisanceRacing yes I'm using vent tube extensions
Try taking them off or shortening them and see if that changes or leans it out.
Do you HAVE to use a double pumper? I have a dual line single pumper laying around, could I use it? Thanks
I do not think a vacuum secondary carb will work with the Hanger 18 modifications, if that is the type of carb you are referring too.
looks good but i wouldnt use zip ties. they get super brittle fast with that much hot air moving over them.
I would agree, thanks for the tip!
Did you drill your power valve holes bigger?
I Did not, I figured with running low boost it would not be necessary, and while I did not have the car out much, it seemed like the AFR stayed good without drilling them out.
Hello. Would this work on a Holley 4778-8 double pumper? Looks exactly like yours 👍
Yes, I'm pretty sure that was this carbs model number ,it was stamped on the choke horn before I chopped it off.
@@NuisanceRacing thanks for the reply. I appreciate it. Did you ever have any leaning out issues with your set up? I did see the tuning video. Very informative👍
@@Dontfearthereaper001 from what I can remeber I think I had some issues of it being to rich, I have sence switched to EFI.
is that it? i glanced over the mods from hangar 18 but i didnt realize it was that simple...
Yes pretty much, except for "Drilling the Power Valve Channel Restrictions" .
Charles Thorpe look up for the edelbrock blow through conversions if you want to see something a bit complicated XD
i deffinately have to seal the throttle shafts, its squeeling like a pig even at idle, i've ordered some tiny lip seals, i'll let you know if they work later this week i hope.
What kind of power do you think this setup is good for?
Not a clue, in the past 2 years I switched over to Holley EFI on the car.
This is obviously a great video.
how do you attach the metal line to the carb vent? i dont wanna just stick it on ther and hope it stays
BOHYDRUS it stayed with rubber line and hose clamps until my most recent video where I switched over to fuel injection.
ok , i just pulled the short vents out with pliers ,ther only 1/4 inch in ther . then i put my new lines in ther and clamped them together so they wont move or fall in if one happens to come out ,but they fit tight . i used my old transmission line was perfect size .
oh yeah i flared the end so to catch some air too
Great idea!
Now what about the choke setup. Thats removed with the flapper correct??
Yes choke linkage was removed with flapper
someone else set up my carb and it keeps starving for fuel under heavy acceleration your comment on the regulator set off alarm bells in my head i have a vaccum line run to the regulator but i suppose its not a vaccum line under boost. suggestions?
how much boost are you at under " heavy acceleration"? is it a boost referenced regulator,some stock regulators have a vacuum line ran to them but are not made for boost.
+Drew Fetters. its a mallory 4309 regulator id say from 15 to 25 lbs i havnt got it dialed in yet i havnt checked the specs on it yet someone else set up the car and ive been patching it up
what carb is it? what size fuel line are you running ? fuel pump size? what engine? thats alot of boost.
+Drew Fetters stock miata pump atm i had an aftermarket pump but burnt it up running both at the same time stock size fuel lines i think both are 5/16 lines its a ford 2.3 out of a turbo coupe 2 bbl holley carb i assume its a 2300 havnt run the numbers yet been thinking about pulling it and going through it to see what hes done
+Drew Fetters the regulator says it increases fuel pressure for every psi imight be flooding under hard boost but tome it seems like its starving
Did u change the floats ?
In the video? Yes at 4:30
GREAT video man......Im in the process of building a FI mustang over on my channel #shiftwrenchrepeat and this really helped me!
Glad I could help!
Do you have jet extensions or opinion on jet extension?
Yes I did have them installed, in the rear. The foam/Nitro float is notched for the exstentions ,and they help with fuel starvation on heavy launches.
So what happens to the choke? Is it hard to start?
I sence went to EFI ,it wasn't to bad to start, cut the choke tower off for better flow from the intake hat.
what fuel pump and regulator did you use for your build? I doing a carbureted 5.3 with a single turbo. any help would be great thanks
+67JD110 Pump: SUM-G3138 Reg:MSD-29388 .Shoot any question you have my way,ill try my best to answer them!
How much boost were you running without opening up the PVRC?
I belive around 7psi.
@@NuisanceRacing thanks man doing a blow through on a 351 and I didn’t expect you to reply honestly. Appreciate the info. I think I might start out with 5 or 6 pounds to get my feet wet and hold off on drilling the PRVC out.
@@whatsunsky4591 Good luck!
@@whatsunsky4591 if you look through my other videos their is one where I am tuning the blow through carb.
👍what are you’re jets size?
Depends on boost and engine size
Dis u actually run this one with turbo?
Yes sir! works good. I will be doing a followup/update video in the spring of how I tuned it and how it is doing.
Where did you buy the floats?
Jegs or Summit Racing has them in stock!
What are they called? Nitrophyl?
Yes sir. I used this one for my 4150 :www.summitracing.com/parts/hly-116-3/overview/
Hey idk if you reply to these still but I'm trying to turbo a 350 tbi any help would be greatly appreciated ! Please get back to me
Nate Gerdom I have never messed with TBI, I would Google it and see if you can find anyone that has done it with TBI ,research is key when turboing a vehicle or doing a large modification to one.
Nuisance Racing I've done so much research but I trust what I've read as much as I trust the random people , im not entirely sure what size turbo I should use , if I need an inline fuel pump , bigger injectors ? Boost refferenced fuel pressure sender ? Wide band o2 ? And what sort of tune do I need to get away with at least 7 psi
Nate Gerdom search up what size turbos people put on 350s, that would be your best bet, will probably need boost ref regulator, fuel pump,wide band O2 for tuning and possibly bigger injectors. As for tuning,I have no clue, I'm sure people have tuned TBI before but you going to have to research that one too.
Where do you get nitrophyl floats
Summit racing or Jegs have them.
@@NuisanceRacing okay sweet as
how many lbs of boost are you pushing
+67JD110 Was at 10psi, have hit as high as around 14.
+Drew Fetters hey bud where are you running your vacuum line for boost pressure? Intake or from the turbo housing?
Right after the turbo on the black pipe( can be seen in other videos.) If you are not running a boost controller and you are using a cheap wastegate ,you will have a boost leak through the wastegate, and will be a vac leak if you run it from the intake.If you need a cheap boost controller Id suggest a NXS Manual Boost Controller.
I can't believe it runs at all
how's cold starts?
+garagemodz1 Not bad,just have to throttle it until it until it warms up.
What size of carburetor is that ?
650cfm.
@@NuisanceRacing Thanks for your wealth of knowledge , I have a 600 cfm I want to convert
How about a motorcycle carburetor?
I'm sure you can, might be procedures to modding it due to that its is a different type of carburetor, I am sure people have done it though.
I did it on my snowmobile. It’s not easy. The fuel pump/pressure issue is the hardest to overcome. But it does work. It’s a lot more involved than a regular car carb set up.
Why not just use drawl through what's the disadvantage ❓🚩
That was an option that I weighed, but due to engine bay size and it being a V8, Putting the carb on inlet of Turbo i feel the piping would be to long and fuel could puddle in tubing before it makes it to intake, and I believe it could have a Hard starting issue. Now If it was a old style 4cly I would have probably done draw through.
After you pay to have the choke horn milled off, you know you're gonna use a Dremel to chamfer and deburr the edge to blend it into the venturi. Why pay good money to mill it when it's just as easy to use a hack saw. Saw it off, then deburr it, and spend your money saved on something else.
exactly what I did, just hacked sawed it off.
I wouldn't attempt to use this setup it is pretty hokey. The theory with the fuel regulator is not that you're pushing fuel back in the lines it's that the engine needs more fuel underboost- without a boost referenced regulator,
The bowls will run dry.
Correct, I miss spoke. Well the hokey setup works pretty decent : ruclips.net/video/ng4KpBz2FQ0/видео.html
Thanks for watching!
You mustn't be real up on your blow thru setups because these mods do indeed work for plenty of guys that dont have a grand to spend on a carb.
Obviously I disliked your video, because obviously you say obviously way too much. Obviously you need to take a public speaking class. Obviously!!!
Thanks for the input Chris!
You're a douche obviously.