Help with pre ignition ping

10.5 to 1 comp isn't always that street friendly with iron heads. Especially open chambered heads. Do you know what cam is in it and if so what are the specs? With 10.5 to 1 compression and open chamber iron heads you'll need a fairly decent sized cam (240 @ .050 minimum is my guess) or it'll have so much low end cylinder pressure it won't run on pump gas. My 360 is 9.8 to 1 comp. with X heads and a Lunati 234 at .050 cam and it won't allow more than 35 degrees of timing on 93 octane fuel without spark knock.