Generally speaking, its not a good idea to pull the head on a well running engine. There are all sort of things that MAY go wrong as a result of pulling the head. If the engine is well cared for, the timing chain will last the life of the motor. So will the rails. There were some problems with head gaskets, but if its not leaking, overheating, or mixing fluids, I'd leave it alone. Head gaskets are not PM. If the chain isn't "stretched" past its wear limit, I would leave it alone.

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Brian Toscano