Strange valve damage
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Senior User
Joined: Jul 2004
Posts: 484
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From: Roland, Ar
Strange valve damage
I have a '89 302/5.0 and was running down the hwy at 70mph when there was a loss of power, I pulled over and at idle there was a bad miss. I drove the truck home and after inspecting I found cyl #5 had no compression. Today I pulled the top of the engine and when I had the valve train removed I could tell that the intake valve stem for #5 cyl was about a 1/8in higher then the rest of the other valves. After the head was removed I could see that the face of the valve was not flat but concave, what would cause this to happen?
Laughing Gas
Joined: Nov 2002
Posts: 1,198
Likes: 9
From: Fairmont
I have seen damage like this a few times. It almost always happens to the intake valve. Usually it is from to much heat. The intake valve is not made of the same material as the Exhaust, and therefor cannot take the same temps. Now getting hot does not always mean the water temp, combustion temps can get high if there is a lean condition. A leaky intake manifold may have a vac. leak, making the mixture lean, and also being a corner cylinder may say an intake problem. #5 and #1 seems to be the worst cylinders for problems.
