Thuming and Pinging

[kenny21]

I'm getting kind of worried about driving my 68 Stang around. About 2 weeks ago
I heard a knocking coming out of the engine while idling. Now when i take off from a stop it starts pinging real bad. I always put the high octane gas in my tank and I just changed the oil. So I'm really unsure what it is and worried about driving it.
The engine is a rebuilt high performance 289. If anyone has some ideas i'd be glad to hear them.

 

[geostang351]

Is your distributor hold down lose to where it has moved during operation?

 

[krash kendall]

Yeah, it sounds like your timing is way too advanced, especailly if it only runs on high octane. Your idle knock is probably detenation. Back it off to between 8-10 degrees and try running on regular or midgrade gas.

 

[ForceFed70]

Definately time to get out the timing light.

To clarify, detonation only occurs when the air/fuel mixture ignites on it's own accord instead of the spark plug igniting the mixture.

Detonation can cause pinging...but so will too much timing. Detonation at idle is very rare and probably not your problem.

 

[kenny21]

K
I've backed off the timing and its still doing it. Could it be noisy lifters? I'm really not sure or how to find out.

 

[kenny21]

By the way i'm not getting the thumping during idle anymore so i think the timing did the trick for that one.