95LSS

I searched for any pictures of a burnt valve but the only pic was not available. The only defination I could find of a burnt valve was: A valve that is no longer sealing properly due to some material build up on the valve. Is that accurate?

My mechanic thinks I burnt 1+ valves in the #3 cylinder. Compression was 60lbs and the plug showed definate signed on detonation. FYI, the engine has 189,600 miles on it so it was probalbly just normal wear/tear that caused it.

motoman

It could also mean that the valve does not seal properly due to distortions from being overheated.

95LSS

Got an update from my mechanic. I burnt 2 of the valves really badly. The gasket mating surfaces looked fine, no evidence of any leaking, so we think it was just the age of the engine that caused. He told the machine shop to save the valves for me.

Stewie

A burn valve wouldn't cause detonation. Your mechanic should have done a leakdown test before he removed the cylinder head.

Detonation would most likely be caused by excessive oil consumption in that cylinder.

Any engine with that kind of miles is not going to have perfect exhaust valves anyway. And also, if the combustion temperatures were hot enough to cause detonation, you can bet that it's hot enough to burn the valves too.

I would check the car really carefully before paying. Take a ride around and ask him to pull the plug and look for a nice brown tip. If it's still white I wouldn't pay.

95LSS

It's very possible that given the age of the engine that the valve seals were leaking. The car was burning a little oil, maybe 1/4 quart every 500 miles. I attributed that to old age and driving >300 miles/week. Needless to say the car is going to get fixed. If the head can be saved I may get a mild port/polish while it's at the machine shop.

Which tip are you referring to: electrode or ground or insulator? The electrode historically speaking is usually a light grey.