Originally Posted by Northern Chevy
So throughout the repairs or tear down of the top end, did you ever really nail down what was causing this "rattling" ... was it valves floating with really weak springs or perhaps preignition due to an extreme amount of carbon build up and was that from too rich a fuel mixture or was it using excessive amounts of oil ? . Then the matter of the mystery air loss in two cylinders as you pressured them up. Just curious to find out what was really going on inside that engine.
I'm going with the extreme amount of carbon. It was really caked on the piston faces and the heads were covered in sludge. This was most likely caused by oil getting sucked up through the PCV valve since my valve covers had no baffles. It also looked like there was an issue on the old head gasket between those 2 cylinders. The gasket came of clean and you could actually see an issue.