Many thanks for the responce to my question/problem of backfiring thru the carb as a timing chain problem (it was). Now that the engine is out, I'm thinking rebuild. I'd like to hop it up a bit, but not so much it's a pain to live with. My questions are, what duration and lift cam range would you suggest (not solid lifter or roller type) and can I get away with 10 to 1 compression pistons or should I stay with 9:1. It's a 72 Pantera with stock heads, torker manifold & 650 Holley and headers. Thanks again for the help. Oh, and one more thing, what should be maximun timing advance at say 3,000 rpm (no vaccum. Should advance be all in at that rpm range? What would be maximun advance degrees for these engines.