Are you speaking of an accelerator pump cam?

Depends on what carburetor, what size accelerator pump, engine build, nozzle size, ignition set up..... Everything.

This is like asking what shoe laces you like the best.... The information you get will be completely irrelevant.

What do you have cooking, let's go from there.

GT

First, there is a lot you can do to a vacuum secondary carburetor to make it work well...


Second, is it having an issue taking throttle from idle?

GT

Only if it pops while under heavy acceleration to wide open throttle, the accelerator pump is "all in" by that point. If this is a standard square bore Holley vacuum secondary, the spring should be the lightest yellow one. One thing that happens sometimes is the fuel pump falls behind under heavy acceleration. One way to prove that is with a fuel pressure gauge at the fuel line. Pressure really can't be under 4PSI and never over 6PSI.

Ignition timing could be funny too. I have seen sticky mechanical advance mechanisms cause what you describe. Easy enough to prove, run a timing light on the balancer and speed the engine up watching the timing advance, it should be quite smooth and increase and decrease with RPM....

Also depending on what carburetor, you could have a gummed up power valve. Or just the wrong power valve. I like the power valve to come in extremely late in the rpm range, you don't need the enrichment at 6.5", you need it at the upper registers so I like using a 4.5". This could change given your set up, but should be silly close... It also sounds like there could be some acc. pump issues, ensure the check ball isn't froze up or missing and make sure the nozzles are clear....

GT