I am looking into a newly rebuilt engine that has a knocking sound. The valve train was worked with and the knock never left. The engine then came out of the car again and I am taking it apart to find the problem.

I found gray sludge in the engine and in the bottom of the oil pan along with some coolant in the oil. I found no problems with the new crank, rods, pistons, or bearings so far. One cylinder had a clean appearance in the chamber and in the ports around the valves. The other 7 showed some black sooting which I believe is normal. The head gasket showed no sign of failure.

Can there be a single problem causing the knock and allowing coolant into the oil?

 

There is water getting in somewhere. Intake gasket, head gasket, cracked intake or cracked head. The water/coolant will leave the chamber clean.

If your're hearing a knocking sound, then chances are it's a bearing. I'd bust out the mic's and check the journals (although a flattend bearing isn't hard to miss).

 

You would say the two are not related?

 

could be knocking from piston slap, or just cause the cylinder with the water isnt firing, and its a dead miss. did the engine over heat?

 

The heads and block are out of different cars. Each were parts cars and overheating could have happened. The heads and block were in the machine shop prior to assembly. If there is a problem with those items, they could have been missed at the shop.

I have not pulled the pistons or the crank. I pulled one main cap at a time to look for trouble. I then did the rod bearings. Nothing unusual. Piston skirts and walls check out good. Only leaves the rings in the short block. I've had no reason to this point to think anything with the cam or timing set.

Coolant on a piston can make that consistant knocking/ticking noise?

 

If there was only a little anti-freeze in the oil it probally
came from pulling the heads.
A picture is worth a ga-zillion words so post a picture of
the head that has the "clean appearance in the chamber
and in the ports around the valves"

 

Coolant was found in the oil before anything was taken apart. Oil drain was first. Also found gray sludge, assumed it was part of the coolant in oil issue.