My son (and partner on the race car project) has a Chevy pickup with a
small block Chevy (350 C.I.D.) It suddenly started "knocking" when he
started it a couple of days ago. It was quite warm, about 90, and the
oil was really thin, I think it was either 5W-30 or 10W-30. The
knocking would seem to come and go in intensity. Today we pulled the
valve covers to have a look at the rocker arms, springs and push rods.
All looked normal. I listened with the electronic stethescope but
couldn't find anything definitive. We pulled the plugs, which looked
okay other than some carbon fouling on a couple. Then we did a
compression check and had 0 compression on #4. I set it to TDC on #4
and the exhaust pushrod was still tight. I loosened the rocker nut by
1-1/2 turns and then had about 30#'s compression. I'm quessing either a
very badly carboned up exhaust valve from a lifter sticking "open" or a
burnt valve from the same condition.
Question: How does a lifter "stick" all the way pumped up?
The cam and lifters were new on a rebuild about 1-1/2 years ago.
Does the analysis of the problem sound right? We're thinking of pulling
the intake manifold and head, renew the lifters and grind/replace the
valves. An alternate solution is to try dumping some "Sea Foam" in and
hoping. Any thoughts??
Thanks,
Tim
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