I have a 1966 200 I6 that I acquired as a core, had the engine rebuilt by a reputable shop, and I installed the motor on my 1962 Comet with a 2-speed Mercomatic transmission. The build happened 2 years ago and I'm just now really getting serious about getting the car on the road. I've put about 50 miles on the rebuilt engine. It's got a knock. I thought it was top-end noise, A mechanic adjusted the valves, set timing, adjusted the carb and the motor became much quieter but still knocking. The mechanic thinks it's bottom end noise. I took a stethoscope and the noise was loudest over the oil pan beneath #4-6 cylinders. Dipstick oil was fine (still has break-in oil in there. Oil pressure with gauge was 50 at idle, 60 when revved. I pulled the flywheel cover and checked the flexplate (new install with rebuild) and couldn't see any cracks. I pulled the oil pan - no metal or glitter in the pan. Thinking it was a rod knock, I pulled the caps off #6 and #5. The rod bearings have light, mild scoring which I can't even feel. All the surfaces are getting oil. I checked #6 bearing clearance with Plastigauge and got .002 (spec is .0008-.0024). I haven't checked the other bearings as I'm not sure that's what I should do. I'm about ready to pull the motor and haul it someplace for a teardown. Any ideas? Thanks!