3100 Engine Identification

[Century7667]

I've got two of these 3100 VIN M V6 Engines in a pair of GM A-body cars. One is a '95 Buick Century, and the other is a '96 Buick Century.

The '96, which I'm the first owner of, I believe is developing the dreaded LIM failure. I've got what looks like some engine oil in the coolant recovery reservoir. Can't see anything in the crankcase yet.

The Buick dealer replaced the LIM gaskets about 10 years ago under warranty. I don't konw if they used a metal gasket or not. Certainly not Fel-Pro.

The engine also has an external oil leak, which I believe is related the distributor shaft o-ring.

The engine has 144,000 miles on it and it runs great. I'd like to keep her going.

What I need a little help with is:

1. Is there a casting number on the engine someplace where I can positively identify the the engine?

I understand that the metal LIM gaskets are NOT available for non-roller rocker version of the 3100. I'm feeling pretty good about the '96 having roller rockers, but would also like to know about my '95 Buick Century which also has the 3100 mill. It's fine right now, only 96,000 miles.

1A. If I were willing to go to the trouble, can you "upgrade" to the roller rocker heads on this engine?

I'm guessing this is doable, just wanting to make sure.

2. Anyone got a good part number for the upgraded o-ring for the distributor shaft?

Both of my 3100 engines are leaking at the top of the back of the engine block, and believe it's that o-ring that is responsible.

3. While I've go the motor torn down to this point, is there anything I should address? I'll take care of the coolant bypass hose, but is there anything else?

Thanks,
Ken T.

[robertisaar]

the last ~4000 or so A-bodies with 3100 engines had the roller rockers in 1995.

yes, you can throw the roller heads on as well, there may be a clearance issue with the LIM, but i'm not certain what combo of parts it applies to.

[Century7667]

the last ~4000 or so A-bodies with 3100 engines had the roller rockers in 1995.

yes, you can throw the roller heads on as well, there may be a clearance issue with the LIM, but i'm not certain what combo of parts it applies to.

This bodes well then. My '95 was built in June of 1995, very late. Maybe I'll have the roller heads. Then again, the MAF sensor is different, and the oil filler cap is different too. We'll see.

I'm guessing I'll need the entire top end of a donor 3100 to make it work. No metal gaskets for the non-roller rocker heads...or so I understand.

Ken T.

[Schmieder]

If the roller rockers hit the LIM, all it takes is a little grinding and the LIM will fit. But that is a PITA if you never done it before.

These 3x00 motors can easily go 400,000 miles if taken care of. The biggest killer is spirited driving while the engine is cool, piston slap.

[Century7667]

The '96 I've owned since it rolled off the showroom floor, and once warmed is as quiet as any engine I've ever owned. I've heard some really loud 3100's on Youtube, but mine is nothing like those.

My big concern with the identification was to determine if my engines can use the metal gaskets (Fel Pro MS98004T). There's been little info on the topic, and much of it conflicting. I read here ( http://www.automotiveforums.com/t906...n_m_3100_.html ) that early VIN M 3100 engines may not take the gasket, and that they are the ball stud variety. However, I turned over a Fel-Pro documents that said that all the '94-'00 VIN M 3100 engines (L82) will take the gasket, and not to get confused with the VIN J engines which have a slightly larger intake port.

So right now, the question is...are the early L82 heads (ball stud variety) not being able to use MS98004T a myth or not?

Ken T.