94 3100 (M Production) head swap

[gearhead77]

I have a 1994 Grand Prix SE with the limited production M VIN code. One of the rocker arm studs broke and there are apparently NONE in the U.S. from what several parts sources tell me. I found a a set of 1999 3.1 heads I can get at a great price, but I'm not sure if the manifolds will line up. Has anyone EVER attempted this type of switch and if so what were the results?

[IsaacHayes]

Someone on here surely has a stud for you.... Saves you a lot of work.

But 1999 heads will bolt up and work just fine. They will have roller fulcrum rockers but other than that it's the same head. Unless it's 1999 heads that have the large intake manifolds, in that case the manifolds might be a little bit off but should work as I'm doing it the other way around (older heads and newer large port intakes).

[3100 MPFI]

rocker arm studs are EASY to come by, but swapping the heads is a very simple procedure, and MANY have done it.

The thing is, there is 2 different 3100's for 1999. The VIN M L82, and the VIN J LG8. The VIN M is the same as yours, but the LG8 is the large port.

Starting in 1996, the 3100 got ROLLER FULCRUM rocker arms instead of the stamped steel. They are not interchangeable (you can't use the stamped steel rockers on the newer heads, and you can't use the roller rockers on the older heads).

Also, if you want to shop around for just a rocker arm stud, look for the 3100 in the 1993-1995 Cutlass Supreme, 1994-1995 Grand Prix, Regal, Lumina, and Monte Carlo.

[gearhead77]

Anyone have a stud?

I've already pulled the heads, but if anyone has this stud it would definately help me out. It is 10mmX1.5 on the bottom, 8mm on top and has a shoulder as this motor has non-adjustable valves. I have been in touch with every local machine shop and GM told me that they stopped manufacturing them. I've ordered sets from Sacramento, Milwaukee, & Tulsa and come up with the wrong part EVERY time.

[tractorman]

If I was in your situation, I'd probably go get one at the junkyard. These engines are common as dirt... couldn't be THAT hard to find a junked one.

[IsaacHayes]

Yeah if I would of know this a week or two ago when I was at a junkyard I would of picked some up there were tons, even a couple with the covers removed and all the rocker parts lying there..