how to tell if the engine is pinging

Spray IT ON THE STREET BEFORE YOU GO AND LISTEN

I did not hear mine detonating and I broke four pistons in one pass.(w/o NOS) I recorded the a/f during the run and it had spikes throughout the whole run but averaged 12.5:1 but could not hear any noise at all. After replacing all 8 pistons and rings I did not want it to happen again so I jetted the carb up 5 numbers and increased the fuel line from 3/8 to 1/2 inch. The a/f ratio was 10.5:1 with no spikes. You might also want to reduce the timing back a couple of degrees to be safe.