Guess The Compression Ratio
It sounds like you might check your ignition curve and advance settings. Too much advance = detonation. At what point in acceleration does the ping begin, and under WOT only, heavy load, any specific rpm range? All these things can be a good clue as to when or better yet where in the advance curve to retard the timing...or if course it could be purely mechanical, in which case this won't help much at all! But good luck!8)