The fuel i am using with my 347 with a mild cam is supposed to be around 93. I had initially set my timing at 12 with a total , all in timing of 32 at 3000 RPM. Under wide open throttle it began to "ping" or detonate so i had two options, increase the octane of the fuel or retard the timing. I chose to retard the timing back to 8 degrees to stop the detonation.
If you advance your timing and the engine pings then you can damage rod bearings, so you back the timing off 1, 2, 3 degrees (detonation...... fuel explodes before piston reaches TDC which tries to push the piston down as its coming up.)