Shifted from 1st to 2nd around 2500 rpm, started backfiring, then clunking sound, sound would go up & down with RPM, never lost oil pressure, drove home about 1/2 mile this way
(Ponce Inlet, FL)
Have a 1967 Corvette recently built 327 less than 200 miles on motor, Edelbrock top end kit RPM Air Gap intake 7501, Performer RPM heads 6089, Hydraulic Lifters 41-1506, Hardened Steel Push Rod set 9629, Roller Rockers, Speed Pro pistons .020 over, oil is high zinc muscle car from Summit, 4-speed. Car has been running great, haven't pushed it at all, 3000 rpm shifts, just cruz'n around. Last time out at start up, started backfiring then backfiring stopped after a few minutes, ran great 30 min. later shifted from 1st to 2nd around 2500 rpm, started backfiring again, then a clunking sound that would increase & decrease with RPM, drove home 1/2 mile never lost oil pressure, did not overheat. Pulled valve covers, looks OK, everything tight, no metal fragments. Noticed some marks on the roller rockers, there are no marks on the inside of the valve covers. Any idea as to what is going on?