Holley Carburetor: (PART 1) Accelerator Pump Explained

(PART1) Indepth explaination of the Holley accelerator pump.Produced with CyberLink PowerDirector 12

[@kurts7268]

Great videos Randy keep them coming

[@holleycarbshowtosadvice40y90]

We will.

[@americanfreedom1]

Never new there was a brass check valve below the squirter nozzles. My 800 quit squirting on the front pump. I'd assume it's the check valve sticking. Bowl and metering block is fine. Thanks for sharing this knowledge and tricks

[@holleycarbshowtosadvice40y90]

That check valve will stick sometimes especially if not used regularly.

[@MrBubbahunt9]

What is the best cam color for the stock pump on a heavy street car.. thanks for your posts

[@holleycarbshowtosadvice40y90]

I like the pink in most cases there are exceptions.

[@lalitomelgar6634]

best video ever thank u appreciate

[@holleycarbshowtosadvice40y90]

Thanks for watching.

[@jeffm7669]

Great video!

[@holleycarbshowtosadvice40y90]

Thank you

[@antonamalfi]

Hi Randy, if I’m getting slight spluttering happening under load when the throttle is depressed could this be because of my cam profile being too aggressive? It’s fine on initial take off, just not under even the slightest load…

[@immeohmyoh]

maybe need a bigger nozzle

[@holleycarbshowtosadvice40y90]

That sounds more like ignition , ignition will break down under a load, if you have an automatic transmission and you hold the brake and put it under a light load and feel if the miss is there , sometimes you can see the problem on a dark night , ignition jumping and arching, hope this helps.

[@antonamalfi]

I have gone through my ignition system with a fine comb and everything there is working fine, it almost feels as though the engine is under powered until I get some air velocity happening and then it starts to pick up again. The word spluttering was probably a bit harsh here, it’s almost like a lean misfire… I’ve got a 350 Holley on a mildly worked straight 6 3.1L which makes about 200hp @ 4800rpm. The engine was dyno tuned with that carb before it was put in the car but the extra weight of the car has unveiled this issue for me. I’ve watched your other video on drilling out the idle holes in the throttle plate as I have also noticed my idle screw adjustments really don’t do anything to change manifold vacuum, could this be where my problem starts?

[@holleycarbshowtosadvice40y90]

How aggressive is your camshaft, send me your cam card numbers and any other specs like compression ect. , we will try to work this out.

[@antonamalfi]

Holley Carbs: How To's & Advice ,40 yrs of exp. I don’t know exact specs but it’s based around a mild 30/70 lobe separation with 500 thous lift roughly, have 10:1 compression, 3.36 diff ratio and a 5 speed manual. Have electronic ignition with vacuum adv and a base timing set at 17 deg @ 4000rpm

[@billbraski2175]

Nice video thanks

[@holleycarbshowtosadvice40y90]

Your welcome.

[@eztactical]

I have a 1969 mustang 302 with a 4 barrel Holley single pump. It runs well at idle also when accelerating nice and easy on the street and highway. But, when you accelerate real hard to pass someone it sounds like it wants to bog down or misfires. My dad said he replace the carb a few years back because it was doing the same thing and it fixed the issue. Do you think the Accelerator diaphragm is the issue?

[@holleycarbshowtosadvice40y90]

It's could be the accel.pump make sure there is no play in the pump linkage if there is adjust pump lever till you have no clearance at closed throttle next ,with the engine off look down the throat of the carb and as you open the throttle see if you see two separate squirts of gas , if all is good you could need to change accel.pump discharge nozzles to a bigger size but before you do that, make sure your timing and mechanical and vacuum advance are all good and you have a good amount of fuel flow to the carb and also check fuel filter for restriction, there is a lot of things that can cause this including ignition or trash in the carburetor , hope this helps. PS if you are still using points as condenser if your points start closing up it will retard your timing check and adjust your points before setting your timing .

[@davidmotley4207]

Thanks for the video, but the video quality is very poor, blurry to see details.

[@holleycarbshowtosadvice40y90]

David I sorry, I don't know what to tell you they look clear on my cell.

[@yazming1720]

Hi Randy...GREAT VIDEO & EXPLAINATION. ? how do I determine what cam to use & why. Yazmin Venice Beach CA

[@swissarmychainsawadams9541]

I think of it like this: the Accelerator pump is like a shot glass of fuel, and the Cam is how fast it gets poured. If you have light car, where the RPMs can increase quickly you can use an aggressive cam (pours the fuel quickly into the carb). If you have a big heavy car like a suburban, your acceleration will be slower and you'll want a less aggressive cam profile (pours the fuel more slowly into the carb) because the RPMs increase more slowly due to the big load.

[@danwells7691]

swissarmychainsaw i have a plow truck with 1850 and 63 jets .. 29 pump nozzle. 1/4 past idle will bog or pop n die completely rebuilt.. vac. secondary. 6.5 power valve. or how about a light weight or no check valve? and why 2 steel balls

[@holleycarbshowtosadvice40y90]

I'm going to due a video soon on that. Thanks for watching

[@petermoran2204]

Hi Randy thx for the video.. I just got a now 650 holley double Pumper. I'm having an issue that when I turn on the car the carburetor accelerates up to 2000 RPMs with the choke on when I take the choke off it stalls. Any suggestions would help thx.

[@holleycarbshowtosadvice40y90]

Sounds like possible vacuum leak if not check your idle circuit make sure its clean and adjusted properly also it's easy to put the wrong main body to throttle plate gasket on , it will cover your idle circuit hole make sure your gasket matches the holes in your main body of your carburetor, hope this helps.

[@peggyparrow2059]

You forgot to tell novices , secondary spring is tapered, i found a carb with a streched primary spring in the secondary, its bigger diamatet was setting up against the diaphram. Did not work !

[@holleycarbshowtosadvice40y90]

Just remember 30cc pump springs aren't tapered , 50cc pump springs are tapered and taller. Have a great day. The carb i was rebuilding both primary and secondary were both 30 cc pumps.

[@vicc6744]

where the heck do the check balls go?

[@holleycarbshowtosadvice40y90]

If it's a vacuum secondary 4160, you have one in most of the secondary diaphragm housing not all have it , most older models do, also older models have them as a accel pump check at the bottom of the fuel bowl but not usually serviced, hope this helps.usually I don't replace them in holleys, there is a lot of extra parts , rebuild kits fit many different carbs.

[@vicc6744]

Thanks it’s a summit carb that is a cross between the auto lite 4100 and a Holley it was running good and NO check ball under the sqirters so thanks I won’t worry about replacing them there is a cake valve in the bottom of the primary bowl that’s working