hi i have an extra 3800 engine from a 98 grand prix. i want to build it and do a top swap. when i put it in my 2000 monte carlo do i have to retune my computer? or can i run it as it is? thanks

 

Yes you need to do a full tune for a top-swap.

Most w-body vendors sell PCMs that you would be able to use, although 2000-2002 are a pretty hard year to create a .bin file for. They are custom made and hashed together typically.

 

what would happen if i didnt tune it? would a ecm from a gtp work?

 

The PCM is tied to the VIN so your car wouldn't start.

If you didn't tune it, the car either wouldn't stay running, or it would knock so badly that you would seriously damage it.

 

ok thanks.

 

will pontiac grand prix gtp headers fit a 2000 n/a 3.8 monte carlo? i looked up the stock exhaust manifold part numbers, and they both are the same.

 

There COULD be clearance issues with the fans on the Monte.

 

as chibi said you HAVE to tune for a top swap, if you dont you turn your engine into a grenade. the headers will bolt up fine but as he mentioned some had clearance issues with the fans and some didnt.