Low Compression

[170C]

Annual time. #3 exhaust valve leaking (1100 tsmoh). Borescope shows crud on one place on seat & as valve closes it moves up slightly. May have worn valve guide. IA said go fly the heck out of it w/ numerous throttle positions, reck compression. If no improvement, pull valve cover & ck to see if valve guide appears sloppy. If so pull cyl & OH. Any other suggestions? Many say it's hard to get to tbo on a O-300 w/o one or more cyl oh's.

[GAHorn]

Continentals and Lycomings both tend to need cylinder work around 1000 to 1200 hours, regardless of so-called TBO's (which apply to the core engine...not necessarily the hot sections.)
Frank, why risk popping the head off an injured exhaust valve and sending it bouncing around inside your cylinder, perhaps out into the intake manifold and into an adjacent cylinder and wrecking the entire engine? (I've had this happen, ...at night.....fortunately it was on a twin.)

Go ahead and pull the valve cover NOW and check the valve guide.

Even better, pull the cylinder and rework the valve or exchange the cylinder. My 2 cents. (Your $1K.)

[Aeroplane]

Why not lap the valve without removing the cylinder? I've done this numerous times with good results, depends a lot on how long it's been running with the valve leaking as the exhaust gasses will eventually erode the valve and/or seat. Had the same problem recently on mine on #5, brought the compression back up from 55 to 75. You might only be postponing the inevitable but it's worth a shot.

[Bruce Fenstermacher]

I would run it at least around the patch and see if all is well. It likely will be. Next I would check valve guide clearance as I lapped the valve with cylinder in place. The last thing I'd do is remove the cylinder unless all other methods have failed to produce the desired result.

But that is me. I have the know how and the tools handy, required to lap the valve and guide with the cylinder in place.

[170C]

I dropped a valve, reamed the guide an lapped the exhaust valve in #4 several yrs ago-successfully. Guess I could do it again if necessary in #3. I agree, cylinder removal will be a last resort

[170C]

Aryana, I am always open for suggestions, but you've got me on this one. What is an Italian Tune Up

[170C]

Thanks for the definition

[GAHorn]

Just to clarify...I wasn't suggesting pulling the cylinder now... I was suggesting pulling the valve cover and inspecting the valve and valve guide before flying around any further.