I have been chasing some gremlins in the past....Vac. leaks...Timing...Valve adjustment...NOW, I have a weird exhaust "feeling" and symptom...I have a 65 coupe with a 302 (edelbrock rpm intake, heads, cam and 650 avs carb.) Exhaust is not normal...Headers from 3-4 are black and have a strong "push", but the headers from 1-2 are not black and have a "weak" push. Same thing on the other side...except reversed, 5-6 header has stong"push" and black (rich) but 7-8 have a "weak" push and relatively " clean exhaust... Could this be a valve issue? ... I have the old firing order that I verified with edelbrock with their cam... Engine backfires like a lean condition, but the exhaust smells rich. Any help out there would be appreciated.