Burnt exhaust valves

Ive had a chariot for 2 years and have just burned out the 4th set of exhaust valves. This only happens on no 4 cylinder. Mechanics just keep replacing the valves. After the 2nd set they replaced the engine and head. After 4 months valves on 4 burned again replaced and have now gone again. The problem mut be something feeding no4 cylinder. Any ideas?

I have a feeling its to do with the design of the intake manifold. There was something they noticed when designing them for the 4G63 that if you just have it like a rectangle it wont get adiquate air flow to the last cyl. Maybe the same applys to that one?

Has this car ever sat for long periods of time? Has the engine ever been apart and sat dismantled? The reason I ask is that it sounds like you are running way too lean in cylinder #4. This can be caused by an obstruction in the intake manifold, even spider webs. The other thing to look at is the injector for that cylinder. A bad injector will cause it too burn too lean. Burning lean causes any metals to burn.

i'd go with the injector theory. if there was somthing obstructing the intake, it shouldn't me getting enough air. thats not lean, so it wouldnt be burning as hot

have you tried to flush the injectors.

Im sticking with my thought. It was a problem with some aftermarket intake manifolds for DSMs