Chevy 350 spitting/miss/popping

This is one of those GM Crate Engines from 1991 with the Mexico heads - 76cc, 1.94/1.50 8.5:1 compression, Chevy 350

Upgraded to Edelbrock EStreet Aluminum Heads 70cc, 2.02/1.60 185cc intake runner
RPM Performer Manifold
AVS Thunder 650 carb
Roller Rockers
Lunati Cam 10120702 .468/.489 at .0500 219 duration
New HEI Dizzy with plugs and wires


Runs great with headers and 2.5 inch dual exhaust, but when you get on it from idle and even when cruising - it pops/spits/coughs/misses just a second and then recovers. Played around with every setting on the timing.

Will check for vacuum leaks next, but also found out that it may need an extra shot of fuel and that there are 3 adjustments/positions for the accelerator rod. Does the same thing with a Performer 750 carb - any suggestions?

Check out the Edelbrock site, they have a very nice chart and calibration procedures for their carbs... Sounds like you have a lean condition just off idle, accelerator pump adjustment might get it probably going to need some spring, rod, or jet changes. Edelbrock also sells a kit to get these carbs dialed in and working correctly. Out of the box they all need a bit of tweaking to be right with your engine.

I agree with Dave, it sounds like your idle to mid-range transition is lean. The first thing is to get your jets & metering rods right for your engine, and once it's jetted right you should be able to take any stumble out with accelerator pump adjustments. Edelbrock has some good Tech videos that they suggest you watch once you've selected your carb, to walk through the tuning process, link here - Edelbrock.com - Tech Center - Carburetor Installation and Tech Videos