Cracked valve ?

My compression is 75/80 in all 4 cylinders. I stuck a borascope in and saw this on one valve. Is this just the edge of the a led oxide deposit? I have a hard time believing the cylinder would test 75/80 if this were an actual crack. - Thoughts?

assume you are referring to the white line? Those are just deposits on the valve and they can make all sorts of shapes and patterns. Valves rarely crack and even more rare to crack somewhere other than the stem, close to the tulip. Cracks in intake valves are even more rare.

Larry

pa38112 said:

My compression is 75/80 in all 4 cylinders. I stuck a borascope in and saw this on one valve. Is this just the edge of the a led oxide deposit? I have a hard time believing the cylinder would test 75/80 if this were an actual crack. - Thoughts?

Click to expand...

Lead "salts" (another word for crystals). You can see in the top of the first photograph some dots of crystals lining up with the line of lead crystals. Shouldn't cause problems. Next time you look that pattern will likely be gone. I am old enough to remember when we couldn't look. Less to worry about!

The environment in a cylinder at work is a hellish place. Those valves, be they exhaust or intake, are under a lot of stress. I am not sure I have heard of a valve "cracking". If it did, it would likely not last very long.....

I had what appeared to be the exact same thing. Showed my local mechanic and he was concerned as well. Thought the jug should come off for inspection of the marks. I removed the jug and guess what. The "cracks" rubbed off after wiping with a cloth. Had I kept the photos, I'd post one now.

One thing you can do is see if you can get something through the plug hole and get lucky enough to get it running across the valve face. See if the "crack" changes in appearance. Something like a Q Tip taped to a wire or something similar with the borescope in the other plug hole.