Cutting out at takeoff

[essentialt21]

Hello again,
Car is idling great, starts great, drives great and takes off great from a strong pedal, but if i feather the accelerator and do a slow soft takeoff from a stop the car cuts out and almost dies on me. I can remedy this by punching it real quick, or really lightly increasing the gas till it gets over the "hump". This is driving me insane. I have a 1966 plymouth belv II with 225 and a holley 1920. Holley was rebuilt, timing adjusted, valve lash adjusted, just replaced fuel pump did fuel line re-route, also checked the accelerator pump and that has a nice healthy squirt, the choke is fully open when it is warmed up to drive. The one thing I noticed is that there is a slight vacuum leak at the holleys throttle shaft bushings, I am wondering if this leak is even significant enough to present itself as an issue, having a bad feeling this could be my problem. Any and all advice is welcome, this forum has taught me a great deal.

-Shane

 

[coloradodave]

A few things to try: See what the accelerator pump squirt looks like when you slowly move the throttle, mimicking a slow take-off. If it dribbles, adjust rod for a longer stroke. Check that the float level is correct. Advance timing a couple of degrees at a time. BTW, the carburetor base can be re-bushed to tighten up the fit with the throttle shaft. Unless it is really sloppy (can you see visible movement other than a few thousandths?) I doubt that your problem lies there.

 

[Photon440]

X2 on coloradodave's advice. Just because you see a strong squirt of gas from the accelerator pump when you go wide open doesn't mean that you're getting one with light throttle. As well as ensuring that the adjustment is right, you can also get different pump cams. You might need one that gives more light throttle squirt.

 

[coloradodave]

I don't think those Holley 1920 1 barrel carbs use pump cams. I'm putting my money on a low float level...

 

[Cranky]

I ran at least 15 degrees advanced on my 66 Belvedere /6 and anything less than 10, it acted like it didn't want to go very good. I also jetted up the Holley, ran an open element air cleaner, straight pipe, and flex fan. With this tune, it went from running 22's at the track to mid 19's. Ball of fire eh! Timing was set to 0 when I first got it. Where is yours set? What's the vacuum advance doing? Also, these carbs suck when it comes to the pump squirter working well when the throttle is opened slowly but it just depends on how slow you are going with it. And what do you mean when you say you feather the throttle? Are you pressing up and down quickly but not moving it very much?

 

[essentialt21]

Timing is set around zero I'll bring it back to around where you suggested and see how it goes. By feathering I just meant I'm going real soft on the pedal when accelerating, I adjusted the accelerator pump linkage a few different ways and the problem is still apparent.

 

[essentialt21]

Also brought float level up a bit but to be honest it wasn't far off

 

[747mopar]

Your timing was set at zero degrees?

 

[Moparsmitty]

The Holley 1920s that were from 70s cars were jetted and adjusted to run pretty lean and any vacuum leak is going to make it even leaner. Hook up a vacuum gauge to the intake and see what it reads. Probably should have at least 12 to 15 in. of vacuum I would guess. If the throttle shafts are sucking that much air I would try to find a carb that's in better shape. I would also set the timing at 6 to 8 degrees BTDC and go from there. Good luck.