Intermittent low speed idle

[Argess]

I've got my engine running quite well now, cept for one little problem. Sometimes when I get off the throttle, my idle drops too far and seems to stay there. I gentle tap of the gas pedal clears it and then it's fine.

I've seen dashpots to slow down the carb return to idle position before, but not on a Holley, which is what I am using.

My idle mixture screws are set for max vacuum, so I'm unclear as to how the engine seems to be loading up with fuel when I get off the gas.

To complicate matters, my dist is actually a bit advanced at idle, so I'm wondering if that may be part of the issue, but seeing as how a quick stab of the throttle clears it, I am leaning towards a fuel issue.

I have one thought so far. Float bowls flooding under acceleration. Fuel flows to back of bowl, floats drop a bit, fuel flows into bowls, and when I let off the gas and car stops accelerating, resultant fuel level is too high and idle is rich. If this is the case, I'm not sure what to do about it as lowering the float level may cause other problems.

The problem does seem more common when I have accelerated up a hill, but I need to re-check that. And now that I think about it, I'm not sure, but I may have had this problem on and off before, but not as bad or as often. However engine is up on power (due to tuning) than it ever used to be, so car is probably a bit faster.

Oh...it's a twin Holley set-up.

Any thoughts?