Will a '91 3.1 be a direct bolt in to my '89? Please, I don't need to be preached to about the glory of a 3.4. This is about me needing a new engine and having a 3.1 available to me. What do I need to do for this swap?

 

More likely to get information on the V6 forum than the Engine Swap forum.

Prepare yourself for a moving experience...

 

direct bolt-in. Remove the 2.8 plenum from the 2.8, slap onto 3.1, remove 2.8 from car, bolt 3.1 into car, turn key.

 

Swap upper intake and fuel rail also for the CSI injector.
remove a plug in the right-rear head for the fan switch.

But for the most part, it is direct swappable

 

Direct bolt in..



And so's a 3.4!!! *just ribbing ya *

I actually prefer the 3.1 to a 3.4 - lower compression ratio = more boost

 

Mmm.. forgot about the fan switch. But there's no CSI on either motor (88 and up). Only reason I mentioned the top end was to camoflage the 3.1 since they're externally identical and to get the 2.8 injectors in so the MAF tables aren't off.

 

A couple things about this.
1. Some engines need the upper 2.8 plenum to allow for hookup of the stock emissions system (IIRC, the 3.1 has no vacuum tee in the back of the plenum, from when I saw the plenum on the current engine, someone correct me if I'm wrong).
2. I am currently running 3.1 injectors with no problem with my 87 2.8 ECM. However, I need to install the damn cold start injector so I don't have to hold the gas pedal on cold starts .

 

Mav, you pulled your CSI out? How'd you plug the holes? Or are you using a 3.1 fuel rail, and the CSI is still in the manifold but not hooked up?

Yeah LD1985, everyone's nailed it down- easiest way is to just sit both engines side-by-side, you'll be able to see the differences. If you've got access to a digital camera, take some pictures of both engines "before" you start exchanging pieces.

For some pictures of a 2.8-to-2.8 swap, which would be similar to your 2.8-to-3.1 swap, see here: http://www.geocities.com/tomp_3rdgen Note that you won't be taking the heads off, so "ignore" the first 4 pictures, you won't be tearing either of the motors down that far.

Wow, those pictures are old. I just noticed that one of the pics shows me with a beeper clipped to my jean pocket!