Cause of Burnt Valves?

[lionheart03]

After finally getting my 91 Camry with a 3SFE up and running, now I'm trying to figure out why a exhaust valve burnt at only 170K miles.

A little background on this car. I bought it real cheap a year ago. The car was drivable when I bought it, but needed quite a few repairs. I seriously doubt that any preventive or routine maintenance had ever been performed on it by the previous owners.

I have been told that cooling problems can cause a burnt valve. Well, the T-stat had been stuck open for god knows how long when I got the car. The radiator also had a slow leak, and signs that it had been leaking for a long time. So the car overheating in the past was a strong possibility.

As for valve clearance. All seemed within specs before the rebuild. Going to recheck everything this week since the rebuild. If something was way off here, that could also have been a cause as I'm told.

I'm really open to any ideas to what may have caused this, so I can possibly prevent it in the future.

Thanks
Jeremy

[toyomoho]

The engine had been rebuilt before the burned valve?

[lionheart03]

Sorry, didn't state that in the first message. The car motor had NEVER been rebuilt to my knowledge when the valve burnt. I have since had the head rebuilt, and put the car together myself.

This was my first motor rebuild of any kind, and so far I haven't screwed up too much in the process. The car runs great now. I did notice that there is a slight tick sound from the top of the motor, didn't pay attention before if this is normal or not.

[Doctor J]

My camry's engine has been cooked by the previous owner who tried to escape from law enforcemet officer [bad idea to try on family wagon]; this caused leaking exhaust valve in cyl.1
Removal of T-stat can cause overheating under load as 1/2 of the coolanrt will go around the radiator in bypas tube [that is why removal of T-stat should never be done if it has 2 valves]