QuestionOk I played with the timing nothing changed the noise, took valve cover off, on #6 cylinder the exhaust valve is just hardly moving at all, swap lifters around for a valve that was working good, took cam out, that lobe for the #6 exhaust was shaved off, the lobe is about round as a ball, it had metal shavings wraped around the camshaft, could that be the popping problem?
Followup To
Question -
I have a 1963 chevy 2 ton truck with a six cylinder engine, I put on new coil, cap, wires, plugs, points, carb kit, the engine runs real good and starts right up, but on the top end of the rpms it has a popping sound threw the carburetor, let off the gas pedal and it goes away, go up guessing 400 rpm and there it starts popping again, it only pops at high rpm?
Answer -
Hi Cody,
Back the timing off just a little bit. It may be advancing too much, and firing when the intake valves are still open.
Van
AnswerExhaust valve not opening? Sure, that could cause popping through the intake. It sucks as much air and fuel in as it can, fires it, but no place for the exhaust to go from that cylinder, and it is still pressurized in there when the intake valve starts to open, thus the pop, or actually a backfire almost.
Accelerating would advance the timing, and the mixture would be richer, so yes, I would say a new cam and lifters will probably fix it up.
Be sure to flush all the shavings out of the oil passeges, and make sure the oil supply passages to the cam bearings are not covered by the new bearings, blocking oil flow.
Van
