How can I tell for sure? Built 350, just put on 64cc heads so my CR is around 11-1, good power but has a funny sound to it when I give it any gas but not at idle, sort of a flapping slapping sound plus when I get close to pipes and mufflers I hear what sounds like a ping.

I've never experienced dentonation so I'm not familiar with it.

I'm going to mess around with the timing today and see if that helps.

Thanks for any help.

1972 Chevy Cheyenne

http://pg.photos.yahoo.com/ph/aikidojiujitsu/album?.dir=dbe7&.src=ph&store=&prodid=&.done=http%3a//photos.yahoo.com/ph//my_photos