Preignition or detination?

[cmpcpro]

Hey all, I took a trip out to Chatsworth today (PAW) which is about a 15 minute freeway drive away, and when I got off the freeway, and punched it at the light, I hear a real bad knock. So, I let off the gas and drove it normally, and it was fine, after a few red lights, if I got on it again, it was gone. So, before I left Chatsworth (Actually went there to get bigger jets for my carb, which really helped!) I retarded the timing (Was probably around the 15deg area) and filled it up with 93 octane (Much cheaper in Chatsworth than Burbank!), and drove home. It didn't seem to knock at all on the freeway, even when I layed into it WOT. And when I got off the freeway it was fine too.

Because I had the stereo cranked the whole way there, I don't know if it was knocking at some point on the freeway, I don't think it did much as I didn't get into the 3k RPM's for very long, and it stayed in the high 2's. Could I have hurt anything? And what could it have been I was hearing? Detination or preignition? It seemed to only do it becasue I was on the gas for so long with no stop. As, with much higher timing, I can take a hill at WOT well past 4k and still be fine... Before I put the 93 octane in, I was runing 89.. always have. The motor is a lightly modified 1974 302, with *cries* 8.0.1 compression.

Thanks,

Chris