You either have a slipped cam gear or an improperly seating valve (bent, insufficient clearance). The cam gear can slip 15-20 degrees and not build compression. 15-20 degrees is hard to percieve by eye. Why don't you take some pictures of your cams and post em' up for us to examine. The angles should be similair to the way YZhaulin took his pics. YZhaulin, that was a nice thing to do BTW.