Holley Double Pumper Rebuild With An HP Main Body Conversion

A look at how a Holley Carburetor was rebuilt. A HP main body was used to increase flow. One will most likely need to change air bleeds and possible metering blocks if doing this conversion.

[@StewartPerformanceLtd]

Extremely well done !!!! One of the most professional / seamless "how to videos" on Holley Carbs...., The best video from a private technician. Extremely thorough and easy to follow. 10 out of 10 !!!!! Scott Stewart Haight: Owner: Stewart Performance Ltd. Boulder, Colorado.

[@kylelove927]

Fully agree!

[@gza06955]

Thanks for the great video. Very informative, good camerawork, and a no bullshit approach. Thanks again.

[@lisagarland5062]

Thank you very much for the details of this video. It helped me alot on my750 double pumper.

[@fredbrisbane9851]

Nice vid. Your carb rebuilds are always meticulous. Here's an easy formula for calcualting CFMs: X/1728/2*RPM. X is your engine displacement in cu.in. Divide cu.in. by 1728 (cu. in. in one cu. ft.) to get displacement in cu. ft. Divide cu. ft. by 2 because cylinders are filled every other rev. Multiply by RPM to get CFM. That Holley will become a choke point at just over 6000 RPM.

[@fredbrisbane9851]

BTW, that formula is if you want to find what carb you need for the max RPM you think you want to turn the engine. If you want to know what RPM a given carb is capable of: Cu. in. divided by 1728 gives cu. ft. of engine. Your 407 is .235532 cu. ft. Divide that by 2 to get cu. ft. per revolution. .117766 cu. ft. Take the carb CFM and divide by previous result to get carb saturation RPM. 700 CFM / .117766= 5943.98 RPM.

[@davidgoodwin658]

If you have two power valves on your double pumper you will have to add the power valve protection to the secondary side as well. You can add the new style white plastic gaskets to the float adjustment screw and nut. This way they wont tear as well.

[@hddm3]

Great tip on the silicone

[@jakefriesenjake]

But does it actually work?? Nothing worse than separating gasket mess!

[@TheHypnotstCollector]

I decided to use 700cfm metering blocks on my 800DP. So it says 4778 on the blocks and 7880 on the main body. I put a piece of wire in the idle ports to lean out the idle. My Holley book suggested that... I'm rebuilding it right now and then I'm starting the engine, a 350 chevy with over 500hp and it hasn't been started in 15 years. so I pulled the heads and pan, spiffed things up and then I'll start it in a few days. And make a video. And sell the engine.

[@jeffgagnon4557]

Great video

[@smallblock337]

Real nice job guy! Very interesting! You made a not so necessarily interesting topic interesting..

[@bushmain]

great vid!

[@pedrotalavera3541]

Excellent video. Thanks

[@fatharmonix]

another great video. thanks for the help

[@jonathanleighton8774]

nice video!..ill have to send you my carb for a rebuild!!

[@flippedmysled]

Great carb videos!!!

[@HammerHeadGarage]

Nice video. An ultrasonic cleaner would have done a great job on that base plate. I rebuild carbs for a living and would be lost without my machine.

[@bnut302]

What cleaning solution do you use in your ultrasonic cleaner?

[@HammerHeadGarage]

Simple green, been using it for 10 years and it works awesome.

[@bnut302]

Thank you. What is your dilution ratio?

[@HammerHeadGarage]

about 40% simple green.

[@luckyvasquez1]

Sounds like napolean dynamite's cousin Kip. Thanks good vid

[@Fullthrottle440Garage]

wow, very good video

[@jakefriesenjake]

I tried spraying silicone on the blue or red bowl/metering gaskets like I do with the other grey paper gaskets, but it seamed to take off the color and make a mess. Even if I use brand new non stick gaskets, they want to shred or lift or Peel where the gas touches. What gives? I want/need sweet reusable gaskets that do not deteriorate or stick what so ever! Where to find?

[@angieghostuforick1645]

Great video I need my Holley carb rebuild but I do not know how to do it do you only work on your carburetors or would you rebuild mine Rick askingand if you do rebuild or will rebuild it I will leave you my number so we can talk thanks Rick PS I've watched other rebuilds in the past but you are the manI didn't know all that stuff about them the little things you pointed out

[@donrutter6765]

Power valve protection came standard starting in 1990.

[@luisfernando-pz3nc]

excelent video, amaizing!!!

[@magnatron7734]

Great vid

[@ccsV8]

Hi Oldsmob... Nice to meet you. Congrats for your great video. You do it like easy. One ask, the new main body' barrels, fit with base plates diameter?? Sorry my english. Regards.

[@Moparmaga-1]

I have a 471 cube stroked mopar big block with trickflow 240 heads & a large solid lift cam, I am planning on using a 830 classic hp & want to step up the throttle bore to 850 size 1.75 bore. I hear that the classic hp 850 flows closer to 9something. But I like the idea of the hp 950 which is a 750 with a 850 base although it doesn't really flow 950.

[@Oldsmob455]

I never did ge this carb to work quite right

[@Oldsmob455]

@@Moparmaga-1 Never got the idle circuit right. Probably missed something in the conversion.

[@IBMara]

I noticed you didn't pay much attention, in an otherwise extremely thorough video, to the one way check valve in the accelerator pump which is located in the bottom of the float bowl. Is this a bullet proof part which needs no attention? A leak here would negatively affect the pump's performance. Thank you, Leo

[@Oldsmob455]

+Leo M. Mara Goto 13:30.

[@IBMara]

+Oldsmob455 Thank for your speedy reply. Again, you didn't address checking this valves proper operation. How would one know that it will seal properly or is that just a given? Thank you.

[@Oldsmob455]

Yeah, I kinda glanced over the subject.. Always room for improvement.

[@kylelove927]

Fuckin great video!

[@hiteck001]

whats the best way to deal with those bowl vents? i seem to crack um everytime i remove them!

[@jsnmrphy]

not sure, but the idle air bleeds on the secondary side might be to large on the new main body. I think the new main body is for 4 corner idle vs 2 corner idle. this may cause a lean condition on that side.

[@Oldsmob455]

+Jason Murphy I still have not got mine to idle right after multiple air bleed changes .. Going to try the metering blocks I'm using on it on the original body and see how that works. pita

[@jsnmrphy]

+Oldsmob455 i'm no expert, but I think you may have to block some passages in the main body on the secondary side for it to work like a 2 corner. (do some research on a 2 to 4 corner conversion) I ran into something similar when I bought a 4 corner base plate for my 2 corner carb. I had to make some adjustments on the new base plate to mimic the old one. in the end it worked fine.

[@donrutter6765]

You have to get your idle transfer slots "square" if you know how to do that. Theres a video on here. Basically, start by drilling a 1/16 hole in the primary butterflies and go from there. This raises your idle a little, so back off your idle screw a little. So by bringing less of your transfer slots to the venturi vacuum, it will idle better and give much better throttle response.

[@kylelove927]

Maybe I missed it or maybe you didn't mention it but WHY all the silicone spray? I've never seen or heard of anyone using a sealer of any sort on a carb besides the gaskets.

[@Oldsmob455]

The spray isn't for sealing, it's to keep the gaskets from sticking.

[@kylelove927]

@@Oldsmob455 Makes lots more sense then. Thanks!

[@kevinblackmon6990]

Does the carb have needle valves under each nozzle??

[@jakefriesenjake]

Yes. They are check valves

[@johna7184]

What do you use now that they don't sell Permatex gasket remover? Also where did you get that scraper? Thanks!

[@Oldsmob455]

Didn't know they don't sell that stuff any more..

[@johna7184]

@@Oldsmob455 Yea I can't find it anywhere. Looks like it's been over ten years but do you remember where you got that scraper?

[@Oldsmob455]

@@johna7184 It was part of a cheapo kit that can be found on Amazon or just about anywhere. It's actually a pry tool kit.

[@johna7184]

@@Oldsmob455 Hey thanks! My first car was a 69 W-30 by the way. I was 15 years old and it was mint condition root beer brown with the 4 speed and console. Original interior also mint. Didn't have the original engine but It had a 455 with the C heads. Cast iron manifolds with the Q-jet. Ran amazing!

[@vintagedashboard6810]

What about cold weather starting without a choke? I’m just wondering how much of a problem that will be. Thanks

[@Oldsmob455]

Carbs like this are for fair weather cars, at least in this garage.

[@robertbruneau112]

what was the part number for the main body? how did the carb work?

[@Oldsmob455]

It never really did work quite right. I missed something.

[@ufckid721]

Hi, I have a Holly 4 barrel on my 2001 5.0 Mercruiser , after rebuilding everything on the boat I really should have the carb rebuilt, is this something you could do for me in the off season. I would ship to ya and hopefully it comes out great. PLease get back to me asap, Thank you Don

[@Oldsmob455]

We are not a job shop. Any local carb shop should be able to tackle it for you.

[@rexdiederich1142]

Are there separate needle valves for each accelerator pump squirters?

[@jakefriesenjake]

I would say absolutely, if it's a double pumper!

[@adamforman9264]

You want to sell that old main body

[@1971Frenchy]

Petroleum gel swells O rings fyi