99 3.1 vin M ?

:screwy: 99 3.1 vin M needs replaced. Part selectors cross ref 2000+ 3.1 VIN J and K-"exact swap" or extra work? also lots probs of head gasket on 3.1, but is it caused by the aluminum head on vin J K?--not sure if M alumninum.
thanks

Welcome to AF.

How many miles and what problem are you having? LIM gaskets are a common problem.

Motor shot--must replace--just ?? of vin M interchange with J and K of 2000+

Motor shot--must replace--just ?? of vin M interchange with J and K of 2000+

The 3100 Vin "J" replaced the Vin "M" in the 2000 model year. Not sure of all the differences but the swap will probably work at least between the 3100 engines. As to going to Vin "K" which is the Series II 3800, no doubt the engine will fit but there will be logistical problems. For one you will need the PCM replaced.

What transmission do you have? The M13 4T60E or M15 4T65E. Check the SPID label on the back of the trunk lid.

Also, there are wiring harness differences.

The upper and lower plenums are different between the vin-M and vin-J 3100's, as well as the cylinder heads. There will be many headaches trying to get an EGR valve, heater hoses and such to make the Vin-J fit in a Vin-M car. IMO, other than the crappy intake gaskets GM used on them, the vin-M is a superior engine to the vin-J. It seems that the vin-M can survive an intake gasket failure, where the Vin-J almost always cooks a head gasket when the intake gasket fails. As bnaylor stated, the vin-K will obviously fit, but it's a 90 degree V-6, where the 3100 engines are a 60 degree V-6. Motor mounts, engine wiring harness, PCM among other things are different. You'd be best off doing an apples to apples swap, Vin-M to Vin-M.