Is it possible to place an aluminum plenum for a 3800 Series III V6 onto a 3800 Series II V6 engine that has the plastic one?

97 Bonneville SE 251K

I do not know that anyone has found anything but the plastic composite available.

Thinking of pulling one off of a Buick La Cross 3800 Series III V6@ junk yard (car looks sad, being that its new and was flipped). They want $50 for it. They look the same.

quite incorrect.... the Series III alum upper will work with the Series II....there is a catch...you will need to find a way to mount the TB since it is electronic on the Series III....other than a TB adapter is a bolt on

There are a few catches with converting to the L26 UIM. You'll loose the PVC system since it differs between the manifolds, and I'm not sure if the IAC valve will work. I've also read about the L36 egr stovetop not fitting in the L26 UIM. You'll also have to drill and tap some of the openings in the L26 UIM to make it work.
In terms of performance a L36 throttle body(no matter what kind of adapter you use) will not flow nice with the L26 UIM opening. Heres why:
L36 UIM:

L26 UIM:

A Series 2 L67 throttlebody would work better since it has a round outlet close to the size of the L26. But some tuning may have to be done.
If your main concern is UIM failure, just drill and tap the coolant holes in the LIM and don't worry about it.

Well in that case I'm not even going to bother buying the plenum. I recently replaced this one about a month ago any way so I won't bother. Besides the car has 251,000 miles on it. I don't think putting on an alumium intake plenum will make this engine last any longer then my plastic one. Thanks guys for your help on this and saving me the trouble, AND a $50 mistake.

Look in the for sale section on clubgp.com. You'll find some poeple who have made the L26 UIM work on an L36. Most of the guys over there are trying to get ~$300 for a used one.

I don't think anyone here has tried it....yet. I know mkaake was working on an adapter, but I haven't heard how his progress is coming along...

Dont know where it came from or what vehicle but I have one and pictures to prove it.

That intake pictured is from a RWD FBody application, and will not work on FWD 3800s.

Also, this thread is 13 years dead.

If a thread is more than a few month old, please dont necrobump it.
I see that a new thread for further conversations regarding this topic was now opened . https://www.gmforum.com/general-gm-c...intake-311723/
See forum policy re Bumping Old Threads. https://www.gmforum.com/introduction...2015-a-304557/
Thread Closed.