Holley carburetor stumble fix

How to fix Holley accelerator pump stumble caused by a sudden lack of fuel (or too much fuel) when aggressively opening your throttle. This particular fix (or adjustment) is changing out the Holley 650 double pumper carburetor accelerator pump discharge nozzles on a 66 Chevelle. During the adjust, I found a nozzle gasket and pump discharge check valve on the primary were missing during the process of filming. I changed both nozzles from 0.028 to 0.035. Note- Going any larger then 0.035 is recommended to use an attachment screw with hole (fuel passage) to allow more fuel delivery.
Don't know if you need larger or smaller nozzles? If they are too small, the engine will simply stumble during acceleration. If they are too large the engine will get power for a moment then stumble.
Tags- Holly carb tuning, Holley carburetor, Holley accelerator pump tuning, holly carb hesitation on acceleration #holley #carburetor
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[@kenb1376]

I got a lesson on squirter size from a fellow racer, back in 1997. I had just built a 499 Chrysler B-1 engine for my ‘67 Barracuda drag race car. Carburetor was a Holley Dominator 1050 cfm with .038 squirters. Engine stumbled badly upon stomping in the throttle. I mentioned it to another racer, who had an identical engine and he remarked “BIG shooters!”. I asked him how big and he said .055 and .060, in cool weather. I installed the biggest I could get, which was .053, and it solved the problem. One word of caution, though. Some carburetors (most) Will siphon fuel out of the squirters at full throttle which really messes with A/F ratio. I had one expensive 1250 APD carburetor that basically would almost shut the engine off, I you stomped it hard. I put bigger squirters in it and it ran like crap going down the track. I had to raise the float level way up high, which made it inconsistent ET wise.

[@savagenomore]

dude...you just blew my mind...I have the very same two lighters sitting on my desk in the same arrangement....

[@mancavemaven2288]

haha!

[@vitodelorto1796]

That car is beautiful❤🇺🇸

[@josevelez8150]

Thank you for the video, I have the same carb and it’s doing the same thing

[@mancavemaven2288]

Let us know if you were able to adjust it.

[@jumpinjojo]

You must be in CT. I noticed the UCONN Huskies note pad!

[@chrisguerra355]

Thanks

[@auteurfiddler8706]

Did the secondary not shoot at all when you opened it while looking down the the carb before you noticed the check valve missing? The stumble seemed to happened before the secondaries open. I wonder if changing the cam would have helped. What was the result of these changes? Thanks for showing me that check valve.

[@jeffrevill6492]

Nice ride

[@mancavemaven2288]

Thanks 👍

[@johnmilner7603]

Nice 66 Chevelle SS.

[@vetteman7856]

I have a 750 double pumper and had a stumble as you were trying to accelerate driving at any cruising speed as i stepped on the accelerater it would stumble. Here what problem i had. The accelerator pump umbrella check valves were the cause. Change these out first it's the cheapest thing you'll do.

[@f150bft]

So...did the missing parts fix it or the larger nozzles?

[@jetwake321]

What size engine do You have? I have a 390FE and i will change the nozzles hopefully will fix the problem. Thanks

[@mancavemaven2288]

327 at the moment. I have a 427 in process though. Good luck with the 390! - Mancavemaven

[@bryantracing3022]

How about reverse lights

[@baims8367]

My carb builder says never go bigger then 031” nozzel and never use the tube style .

[@evanfales6399]

What exhaust setup do u have just curious I like the sound of your car

[@mancavemaven2288]

Thanks! headers and flowmasters. Also installed electric exhaust cut offs recently. Now it scares people away. haha. Cheers!

[@chmasy4437]

At point 2:43 your are referring to a book. Which book is that? and is it any good?

[@baims8367]

Valves to tight will do that same thing . Ask me how I know lol

[@melvinashton7046]

Hey is it okay to have the manual choke open all the time? Thanks

[@andreg8192]

So mine bogs on WOT, I adjusted the pump arm and it seem like it work but still bog out, what should I start looking next?

[@bobstephens8851]

It's either getting too much fuel or not enough. What kind of carb?

[@Live4Ibanez]

Go up 2 or 3 sizes of pump nozzle(s)

[@hosscaddy]

So did this work? I have a 770 on my car and it stumbles on hard throttle hopefully this will fix my issue also

[@mancavemaven2288]

It did work! I suppose I should have made that more vivid at the end. Cheers.

[@jacobzoll832]

Did this fix your carb @hosscaddy ?Having the same issue?

[@hosscaddy]

jacob zoll nope. I pulled that pile of crap Holley off and went back to my edelbrock

[@joseherrera9691]

Did you put 35 on front two

[@trailerparkcryptoking5213]

Don’t blame the carb because of your gross lack of tuning knowledge! 😂😂😂

[@saltycrowgarage7215]

That accelerator pump arm is way out of adjustment

[@jasonl3185]

Then buy a stand people would like to see how it came out Boooooo!!!!!