Sorry but this is kind long.
Ok my buddy just rebuilt his 350. New pistoins, Rings, Main cam & rod bearings, oil pump, lifters. Had set of heads checked by a local machine shop and they said they were fine. So he put everything together and fired it up. Started right up, but as soon as it did we heard alittle knock, knock, knock. Then i quit until he REVs it up. So he shuts it down. We could tell the number 3 cly. is not fireing. So we check the plug, fine lots of spark. Dumbfounded on that one. So we fire it up again, knock is still there, but can't really notice it at idel, untill you REV then is really noisy. So we jerk the motor back out, and i take it apart. This was his first time on putting everything bottom end wise together and i wasn't there to watch. So i pull intake everythings fine. Pull pan, waiting to see a rod cap or whatnot missing. But bottom end was fine. Nothing wrong. everyting perfect. So i jerk the heads, and fine tons of oil on the #3 piston, and some on all the others too. So i am thinking rings installed improperley, bad valve seals, valves not sealing agains't valve seats. I know that on the rings one had a Dot on it and had to be install in the first or second groove, but he lost the instructions So i don't remember were he told me he put them. But anyone with any advice on this situation would be greatly appercated. :hail:
Thanks Brad

 

if he lost the instruction you, or he has no idea if the correct ring went in the correct groove or if they were installed right side up or right side down. at the very least replace the rings and read the instructions or leave engine assembly to someone that can and will. as for the sound my first guess was an exhaust leak, second guess was wrist pin or piston slap.