I’m trying to get rid of a slight “pinging” during acceleration. Assuming the timing is set correctly, is the pinging caused by a lean or rich mixture. Also, if I turn the mixture screws in, is this leaning or enriching the system? It's a 1970 350/300 with stock Q-jet.

 

"Pinging" or pre-ignition is generally not a function of mixture although some times a lean mixture will burn a little faster and hotter. If the timing is right on.then a 2 degree retardation might stop the pinging and not hurt performance too much. Recurving the distributor can also help,I've found a lot of performance in this area but not recentlly on whatever it is they are selling in place of gasoline these days. The 383 in my truck is a compulsive "pinger" and the only solution is an octane booster if some kind,too much compression to retard the timing. I believe turning the screws in reduces the air,thus a richer mixture.We used to call 'em "idle air' screws. Good Luck!
Ron

 

Thank you, I'll give the timing thing a try. I agree that the gas these days is crap. I'll also give the gas additive thing. Smooth roads!

 

If the pinging is just occuring upon an initial throttle increase and then goes away, it might be too much vacuum advance. If so, you can get an adjustable vacuum advance unit.

 

Sounds like a timing issue to me.
My exp with bad gas was more of a breaking up and rough idle not pining.

Schoon