I've already seen a 3.9L for sale on ebay, and really I strongly reccomend it. Same trans, just some of the compu-boxes are different. Probably more programming than anything.

Put it this way, the 3.9 engine should be lighter than the 3.8. It's a smaller, 60 degree configuration, and doesn't have to have the balencer assembly like the 3.8. No S/C means it's going to be less of a 'wanted' item, so the price should be more reasonable. Plus, with the smaller engine block, means you have more room to work with when hooking everything back up.

There is less parts available for the 3.9, but keep in mind that makinga customCAI isn't all that complicated. Now I'm sure you can't just swap out a smaller pulley to get more horsepower, but at least you won't have to run premium fuel either.
(though I will note I think my car runs better on it)

Plus, since the 3.9 and the 3.5 share a common of like 80% (I think that's what I heard)of parts if you keep the 3.5 around you know that even if something (other than serious engine damage) goes wrong, you probably have the part to replace it.

 

i think that would be a good thing for somebody like me with a 3.8 n/a engine to consider too. give me a nice extra boost of power. hook up my dynomax cat back and go. so would the 3.8 bolt up to the same tranny a 3.9 will?

 

Not sure on the transmission as they may be the same, but you can't simply dump a 3.9 into your car. You will need new wiring harness and PCM as well. You might even need to splice into your old harness. The engine mounts I'm pretty sure are going to be different as well so you would refab them.

In your case the easiest way to make power is to drop in a Cartuning turbo or similar and upgrade the transmission to HD. That should put you in the low 13's.

 

i was thinking about trying to find a supercharged 3.8 for it.

 

Daniel, actually the 3.9 and 3.5 share a common block (just the bore is diffferent if I'm thinking correctly), actually share like 60, or 80 percent of parts. Can't remember what GM said. 3.5/3.9 are same 60 degree engine really, just the displacement and intake differ. Both have VVT, same mounts (I've looked) same trans, and most of the computers and stuff are the same, they're just programmed differently to handle the different intake and tuning and such.


Ok fine, lemme get the document:

The 3.9L V-6 shares 80 percent of its components with the new 3.5L V-6 (LZ4).

The 60-degree angle between cylinder banks is naturally balanced for a V-6 engine, which requires no balance shafts to cancel out second-order harmonic vibrations. The cylinders are offset, meaning the centerline of the cylinders points to an intersection slightly lower than the centerline of the crankshaft. This was designed to make room for larger cam bearings, and make room for the large bores of the engine. The cylinder bores are the same diameter as those in the LS1 small-block V-8 engine.

 

Yeah the 3.9 and the 3.5 are similar.... But what I was going at was the 3.8 isn't similar. You can't take a 3.8 engine bay and drop in a 3.9. That is where I was going with it.

 

Ok, Yeah, so anyone wanting to upgrade their 06/07 should look into a 3.9, where as someone with say a 2000-05 3400 monte should look at the N/A or S/C 3.8L

 

Right on the money. Going that route you don't have to work so hard on engine mounts and wiring harnesses.

 

 

The 3.5 and 3.9's aren't very common in the grand scheme of things so they don't have the mod options other engines have. This is why there is a huge market for the 5.0 and 5.7's and even a semi decent one for the 3.8's.