C-145-2 Valve too long

[j3pup]

Just did a compression check on my newly obtained C-170B, we found one cylinder low. After removing the cover we noticed that the valve is slightly too long and not sealing properly. This valve has been in the engine for 1,000 hours now, whats the normal fix entail?

Thanks...

[GAHorn]

That doesn't sound "right". If that engine has had previous compressison readings and did not suffer from low compression and a leaking valve...then something as subsequently failed to cause the valve to remain open.

[Bruce Fenstermacher]

Randy asked the same question in a PM and I asked him to call me as I don't have the time to write the book on all the possibilities.

But we know that all the correct valves for this engine should be the same height and that a hydraulic follower is used to automatically adjust valve and rocker clearance and .005 push rods are available if the stock rods won't achieve the correct dry hydraulic clearance.

So if a valve is truly to high and not closing the first things that come to mind are the condition of the valve set and valve face. Excessively worn or broken seats or valves would allow the valve to sit high and possibly not close. If the push rods have recently been removed perhaps there is an .005 over rod in the mix that isn't were it was meant to be. I suppose a hydraulic unit could also jam to high but not likely.

But what is most likely the problem is a stuck valve. One that has to much carbon buildup on the stem and guide not allowing the valve to close. There could also be carbon on the valve seat or valve face holding the valve open.

Cleaning the valve stem valve and seat is relatively easy for those that know how and have the tools. The procedure has been described here and can be found with a search. It is most often associated with the words "rope trick" which actually is a procedure to temporarily free a stuck in the field but can also be used to hold a valve closed will the valve spring is removed.