Loss of compression due to valve stuck open

[bob hughes]

Hi Guys

I have a strange one here, before I take the head off to find out exactly what is wrong, has anyone experienced an exhaust valve being stuck open causing lack of obvious compression. Took the rocker cover off to find around 1/8 inch gap on the exhaust tappet of number 5 cylinder and it is obviously stuck down, maybe something trapped under the valve head.

Bob

 

[GregW]

Hi Bob,
Before removing the head, it might be worth inspecting the valve springs to make sure either hasn't broken, but I'm more inclined to think #9 valve stem is bent. A piece of crud blocking the valve as you mentioned is also possible.

 

[Randy Forbes]

I won't speculate on how, but it's probable that the reason the valve is stuck open, is because the stem is bent.

When you rotate the engine, I presume that the valve will open further, but only cloese to the same 1/8" gap to the rocker-arm?

Has this engine had any recent work done on it?

Might as well start looking for a good deal on a head-gasket set, as I predict you're going to be needing one in the near future.