Chevrolet: Chevy 350 timming, chevy 350, octane booster

Question
I have a 1970 Nova with a built 350, the problem is...I did'nt build it. It has a big cam, and I dont know what pistons...It pings while I drive and runs when I shut it off, I know the timming needs adjusted, but I'm not sure where to set it, I know on a stock 350 it would be 6-8 deg. advanced, but not sure what the degree is on this beast? Could you please give me some ideals.
Thank you.
Mark

Answer
Mark;
Hi well the gas is one reason it is doing that, you can get some octane booster for the tank. If you do not know the cam, pistons than you will have to do it by trying different settings and find the best but I think that it is to advanced at this time , you can back off on the timing  2deg and see if it helps , you might have to turn the idle up , if it needs it. than try it 2 more deg lower if need be. ok you will have to play with it till you find out where it runs the best at and keep a record of the settings.  also check for any vacume leaks.   ok