I pulled the rocker arms off to install my new elim kit and found that what I really have is a timing problem, sort of. Instead of a bad jet valve, when I removed the rocker arms I found that both of the retaining bolts on either side of the #3 exhaust rocker arm had broken where the threads start. I believe that during the ignition cycle either it was not opening all the way or even not at all, causing the backfire and lump. There appears to be a little scoring on the cam, not too deep, but noticeable. So it looks like I'll be installing that non jet head after all. So, the good news is I think I found the problem. Obvious bad news is, more time and effort on a tight schedule.

Two questions for the experts:

1. Are there any shortcuts or gotchas I need to know about that aren't in the Service Manual that will make the cylinder head removal and replacement easier?

2. Are the broken bolts a common problem? I know the the threads start are typically a stress riser, so it makes sense that they would break there. Does the breakage of those two bolts indicate another specific problem for the 4G54 or OHC engines in general?

Thanks.