Question : Identifying 3.1l engine

[1987k20]

Im working on a 99 malibu, has a 3.1l sfi engine replacing the intake gasket. The engine was replaced at some point in the past and I dont know what car it came out of so I dont know if it is a J or M vin code. The car was originally an M but they could have put any of them in. Does anyone know of a way to identify which one it is, as they both have their own p/n's for the intake gaskets. Thanks. Chris

[robertisaar]

does the intake look like this:

or this:


basically: does it have ridges above and below the writing?

[1987k20]

no ridges, but as I recall the original intake didnt have ridges and it is an M vin car.

[IsaacHayes]

All VIN M engines have ridges..

[1987k20]

well I found written on the rear valve cover that the engine was either pulled in 2002 or was pulled from a 2002. It said IN 7/02. Anyone make a guess as to what it was, it supposedly had 40k miles on it.....it aint my car and I had no dealings with the engine swap...so Im left holding the bag on this. Are there no casting numbers on this engine that might tell me something?

[IsaacHayes]

It's a VIN J 3100.. what more do you need?

[1987k20]

Just making sure, dont want to put the J code gasket kit in and it still leak and have to do this job again....I think I would hang myself instead. What are the differences in the gaskets out of curiosity?

[IsaacHayes]

The main difference is the upper intake gasket will be different (since M is small ports)... Which is cheap and easy to get to.. Go for the metal felpro or dorman kit so you don't have the crappy plastic ones again. If the engine looks like the top pic and has 00 or later cast on the LIM then you have a VIN J.

[1987k20]

LIM?

[IsaacHayes]

lim = lower intake manifold
uim = upper intake manifold

[1987k20]

I dont recall seeing anything cast on it, I will look tomorrow

[IsaacHayes]

Look by the top of the LIM near the PCV. But yeah if the UIM is smooth and no lines then it's a VIN J