Well, I spent the end of the summer breaking in the new ZZ4 crate motor. Its been running great, until I took it out this weekend to discover the engine began stuttering/surging between approx 700 and 2000 rpm on acceleration, after that at higher rpm's it runs and pulls great. It almost feels like its misfiring but then goes away at higher rpms. Of course the car was well warmed up, choke opened all the way, ran it for about 45 minutes, so not a cold engine issue. Thinking it was a fouled plug or bad wire, I changed the plugs and wires today. Didnt solve problem (wasted money as usual!). But then I thought perhaps the colder temps outside (50 degrees this weekend) was the culprit, the car has only seen 80 degree days until this weekend. Could it be the carb does not like colder weather and needs to be tuned again? Anyone else ever have this issue?

I have a Holley Street Avenger 4bl Carb, timing set at 14 degrees at 800 rpm 36 degrees total.

Any thoughts on what the problem can be? Its making me nuts.

Thanks...