I am not a Chevy guy, but I have a Jeep with a SBC in it. Small cam, headers, Holley 600 carb. It has had what seems to be a dead miss for some time. I have replaced the plugs with Accel u-groove header plugs, replaced the wires, rotor, distributor cap. Still seems to have the dead miss. I have pulled the carb and rebuilt with Holley parts. No real change. Carb has size 65 jets in it which seems too rich. Timing is advanced a tad, maybe 2 degrees, but even with it not advanced, still have the miss. I noticed last night under heavy throttle there's a weird sound coming from the carb. Almost sounds like the exhaust is coming through the carb. It isn't backfiring, but a weird popping sound like a 2 stroke motorcycle or something. I still have plenty of power. Any suggestions for what this could be? Valves sticking or in need of adjustment?

 

Sounds like it might have a bad valve, or cylinder not sealing. Time to do a compression test to see which cylinder is the culprit. Once you discover the cylinder, then pulling the heads will determine if it's valves or something else. Make sure you warm it up before doing a compression test.

 

Was the engine work (cam, etc.) done recently? Perhaps the valve lash wasn't done correctly, and one or more valves aren't closing or opening as they should. Kind of hard to say with certainty what it is without being able to lend an ear.

 

Sounds like a flat cam lobe to me. Pull the valve covers and crank the engine while observing the valve train.

 

Xlr8tor, keep an eye on dates. This post has been dead for 6 years, no need to drag it back out.