Detonation ping

[Dead Parrot]

I had a 79 Camaro with a 305 that had a minor pinging problem. Manual transmission. If I lugged the engine much at all at slow rpm, would get minor pings. Probably one or two slightly lean cylinders.

Check your THERMAC system for proper operation. If it is stuck on heat, your air mix could be too hot.

Does it want to idle too high? If so, supports the vacuum leak idea. Been chasing a leak on mine. Finally found one where the intake gasket between 2 and 4 had a 1/8 split in it. Did a temp patch with RTV and it is better. Still acts like there is a leak so going to pull the intake and install new gaskets at some point.

Check the riser valve on your exhaust system. If it is stuck partially closed, will both overheat the carb and put additional load on the engine with the increased back pressure.

[kwmech]

The intake manifolds in those years had a tendency to crack through the EGR system and create an internal vac leak. A 305 engine should not have a huge pinging problem unless there another problem, even on 87 octane. When it is cooler out, everything is shrunk down. As things heat up they expand creating a larger leak. Diagnose it or have it diagnosed by somebody that can figure it out. Don't just start by throwing parts at it.