I was changing my oil and removed my skip shift eliminator (tuned out) today and was under the car with a flashlight tracking what might be a small oil leak. Anyways, I happened to look at the back side of the driver's side head, there is a white "X" written on it and just below that is a yellow section that looks like glue residue where (duct) tape might of been. The casting # on the head is 806 and it is using the 98 style perimeter bolt valve covers.

I do know that my PCM was swapped at one point before I had the car. When I pulled the PCM to install the SLP fan switch, the sticker said it was a remanufactured unit. With that said, is it possible the motor or heads were swapped at some point?

Any ideas?

Edit - The back side of the passenger head doesn't have anything written on it and is clean.

 

That would be my guess. I cant see them putting that on there from the factory

 

I might be wrong but some of the 98's had headgasket issues, your car might have been one and had the issue fixed. That would be my guess.

 

Also, there were alot of cars that bent pushrods when the LS engine first came out and the valves tapped the pistons. It may have been a warranty repair. My buddy had this happen on his 99 Firehawk not too long after he bought it new.