Tuning For Detonation

My 340 @9.5 cranking only 155psi would momentarily ping if I abruptly stabbed the throttle from a cruise with vac advance hooked up @48. The vac advance cant drop off enough/in time for the big gulp of a/f and just a for a second.. makes what sounded like a single ping then it was good.
It was a 90's mopar replacement, not a performance adjustable type, made by Mallory for mopar and there were some bad ones that also were out of phase with the cap and spark scattered lighting off multiple cyls causing piston skirt scuffing in no.5 at or near bdc.