Symptoms of a burnt exhuast valve?

[Tquillen]

It was stated earlier that a burned exhaust valve can be caused by an overly lean condition, and this is absolutely correct. Also, it can be caused by retarded timing; if there's not enough ignition lead, the mixture in the combustion chamber continues to burn as the exhaust valve is opening, and the valve overheats. If the lifter preload is set too tight, the same thing can happen...the exhaust valve hangs open, the valve edge overheats, and the valve fails. This is what it will eventually look like.

[jabborabbo]

Originally Posted by Tquillen

It was stated earlier that a burned exhaust valve can be caused by an overly lean condition, and this is absolutely correct. Also, it can be caused by retarded timing; if there's not enough ignition lead, the mixture in the combustion chamber continues to burn as the exhaust valve is opening, and the valve overheats. If the lifter preload is set too tight, the same thing can happen...the exhaust valve hangs open, the valve edge overheats, and the valve fails. This is what it will eventually look like.

Did that valve come out of a “running” (obviously not running well!) engine?????

[Tquillen]

Originally Posted by jabborabbo

Did that valve come out of a “running” (obviously not running well!) engine?????

It did. It idled low, and sounded terrible, but we were sorta committed to making the run. Race car on methanol; the valve got hung open slightly from a pushrod problem on a previous run (long story). Interestingly, I have pulled valves out of daily driven Chevrolet small blocks that looked absolutely identical to this. The exhaust note out of the tailpipe will have a very distinctive sound; once you hear it, you won't forget it! LOL

[Steeveedee]

Yeah, it starts out as a "chirp" that gets less sharp as the gap increases.