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I could not find another section to post this in and I know the people that are on this forum have the answers. I will not say model of car here but I am sure you can guess it. It has a 396, 360 horse power with a powerglide and Holley carburetor. Taking off quickly it runs fine but when I take off slowly it sometimes dies. Without the engine running looking down the primaries, when I open the throttle a good flow of gas is pumped in from the accelerator pump jets but if I move the throttle slowly there is no pumping action. Is that correct? It is the original Holley carb and the points, timing and spark plugs, and vacuum are good.
Off idle stumble, check the float levels first. Then you have have to pull the metering blocks off the carb main body and be sure all the tiny passages are clean. Sometimes a very slow motion of the throttle won't show a visible squirt of gas from the accelerator pump, but just to be sure, check the adjustment. With the throttle fully open and the accelerator pump lever pushed down all the way, there should be .015 clearance between the end of the adjustment screw (it's a hex head) and the pump lever.
well this sounds like a 66 Chevelle SS right down my alley. is your choke working correctly? is this a new problem or has this been this way for awhile? I double check for vacuum leaks and your vacuum advance can. put a vacuum gauge on it while running and make sure it stays steady.
Yes it is a Chevelle. I got the car running about 3 years ago and this problem has persisted. The vacuum is a steady 16 inches (at 3600 feet elevation.). Yes the choke works, but when the engine is cold you have to keep it running for about 60 seconds before the choke and fast idle can take over. I will go out and check the float level and check the adjustment of the accelerator pump lever.
I checked the clearance for the accelerator pump lever and it was good. I forgot, I can not check the float level because when I first got the car running the fuel leaked out of the primary fuel bowl because the bowl was "warped" so I got a Holley replacement bowl. It does not have a fuel level check plug. When I connect the vacuum advance back up after checking the timing the timing advances beyond the timing marks. The throttle shaft is worn a little. When you spray WD-40 around the throttle shaft it kills the engine.
and not all carb re-builders are created equal too. I like custom rebuilt carbs in NJ. others have good look with Eric Jackson, there are few others too. here is my 66SS
Engine dying
