1953 235 "w/Powerglide" engine. I got a call back today from the machine shop about the 848 head (originally from a '56 235). I took it there to have them look at the valves. #1 cylinder was leaking air past the exhaust valve. I removed that valve and the exhaust valve from #2 cylinder for comparison.
The contact area of the leaky #1 valve was not concentric. The contact area of the #2 exhaust valve was concentric, but the contact area where the seat contacts the valve was not centered on the bevel. It was very near the inside edge of the bevel, which is not right. It should be centered.
The guy at the machine shop says that the valve guides are worn out and need to be replaced. The guides were replaced by this machine shop 22,000 miles ago.
2,000 miles ago, this machine shop did a valve job on this head when I brought it in to have it completely overhauled due to a thrown rod.
He told me today that it needs new valve guides, and that the valves are blue from over heating. He suggested that this was from incorrect timing or from running too lean. There is an overheat indicator on the head which they put on all heads so that they can tell if operator error caused failure. That indicator was intact. The spark plugs with 2,000 miles on them look fantastic, and the top of the pistons look unfazed as well. The #1 piston had extra carbon deposits due to incomplete combustion, but it was not excessive in general.
They had put positive valve stem seals on on this head. I am wondering if those were preventing sufficient oil from lubricating the valve stems. I asked him that, but he does not think so. I have to question that, given that these engines do not spray oil all over the place like modern engines which call for positive valve stem seals do.
Would insufficient oiling of the valve stems cause excessive wear and cause the valves to turn blue from excess heat?
BTW, this engine has never gone past 180 degrees, and I never have to add coolant to the radiator, and I drive it as hard as it was designed to run.
What say you?
Last edited by 52Carl; 08/24/2023 12:50 AM.
