Hi everyone I have a little problem, I have a 427 with a holly 850 DP. I have a few problems; first I have a pop coming from my exhaust at low RPM (below 2300 rpm). The second problem is I can't get it to idle. The third is I have no idea what to set the timing at.

At the end of last year I was having trouble with the idle as well. I figured that it was the power valve so I had the complete carb rebuilt. This obveisly didn't solve the problem. The car has been sitting all winter in a heated garage I don't know it that has anything to do with it but I know for sure that it was not popping at the end of last year.

Check the plugs and wires, an almost fouled or fouled plug will cause a pop. My truck will will have a low rpm pop and shaky idle but run and drive fine with a dirty plug.

sounds like a burnt exhaust valve, do a compression test or cylinder leakdown test to verify everything is ok. You can also do power balance test to see what cylinder is giving you the trouble. Or with it idling and some insulated gloves remove one spark plug wire at a time and reinstall listening for the one that corrosponds with the popping noise-that will identify what cylinder is in trouble. A bent pushrod can also cause a popping noise opening the valve late.

I had a problem with my 454 where it would pop and sometimes backfire out the exhaust if I were stuck in traffic and had to idle a lot. I tried many things involving carb tuning and timing. I had also replaced the intake gaskets using the soft Fel-Pro's. When I developed an oil leak at the front of my intake I replaced the gaskets again. This time I put Permatex non-hardening sealer around the intake ports. I haven't had the popping/backfiring since.

I checked all the plugs and wires and they are all fine. This just started after it was sitting all winter. I had the carb rebuilt over the winter and installed a new wiring harness along with a one wire alternator. I don't know if any of that helps but that is all that I changed form last year. There was no pop at the end of last year.