engine popping under acceleration

[Lowerdjoker]

1986 chevy 305 some mods done to engine like 202 heads slight cam. engine starts and runs fine at iddle. rev motor up starts popping threw the carb? replaced cap button plugs wires checked timing & vacum all good. next pulled one spark plug wire at a time to see if it would stop no change. motor has about 3,000 miles since rebuild. some ideas please? thanx

[silicon212]

202s on a 305? How? The bore is too small for those valves!

Anyhow, there are numerous causes of this behavior, including vacuum leaks, a lean mixture, incorrect ignition or valve timing, and/or maladjusted valves, worn lifters/cam lobes or weak valve springs.

If it has a flat tappet cam in it, did you follow the proper cam break-in procedure? If not, you probably already need a new cam and lifter set. What type of engine oil are you running?

[Blue Bowtie]

Silicon listed lots of very good possibilities. I'll try to narrow it down even more - Check the cam timing. Use a degree wheel. Been there...

[luxeryvic]

could be knocking from to heavy of a fuel/air mixture

try tuning your carb

[silicon212]

Originally Posted by luxeryvic

could be knocking from to heavy of a fuel/air mixture

try tuning your carb

A rich mixture will never cause a knock. A lean mixture, however, can.

My bet is on cam timing or a bad camshaft.

[luxeryvic]

oh ok thanks

[HeavyChevy82]

I had the same issue with my 80 Camaro. My accelerator pump was bad, after I rebuilt the carb it ran like a dream.