G6 Engine swap stuff

**deathmetalscottie** · 07-06-2009

Ok, this is my first real post. First this is not my car but I'm basically building it for a friend so I will be handling his questions.

So before, people say it isn't worth it don't do it or you are a nub don't do it, I do have engine swapping experience. I'm trying to get some info before we jump right into this project. Heres the deal, my friend wants to swap the 3.6L G6 GTP engine into his Grand Prix along with the 6 speed tranny. Oh and before I forget, he has an 04' GT with a 3800 series

Engine mounting and other related questions:
1. will the mounting brackets on the GTP engine line up with mounting points on the frame/subframe?
2. I don't think it does but does the 3800 series come with VVT?
3. just in case we do a direct mechanical swap and keep the stock management, will the injector cups and rail fit from the 3800 onto the 3.6L?

Tranny stuffs:
I know there is a guy who has attempted to put a G6 6shooter on his generation before my friends GP. I just need some measurement info from that guy or anyone who knows.

1. Is the tranny a cable or shaft shifter?
2. if cable, does the stock length from the G6 fit the GP?
3. what are you guys using for axle splines? Will the stock splines from the GP fit the tranny?
4. what lengths for the axles do we need to get. We were thinking of getting custom axles made from the driveshaftshop.com but if you guys know of a more cost effective place, tell me please.

Keep me posted, and thanks.

Scott

**Quicklynx** · 07-06-2009

The guy who put the 6 speed on his Gen II GP is njbrain. Search his name and look for his thread. I believe he listed eveything needed and posted most of the directions.

Has your friend considered a LS4 swap? It is a direct swap.

I'm guessing he mainly wants the 6 speed though, correct?

**minichopper6hp** · 07-07-2009

youre gonna need to use the g6 stuff, all the wiring and pcm. none of the 3800 parts are interchangeable and youre going to need hubs for a malibu and possibly custom length axles.

**deathmetalscottie** · 07-07-2009

QUOTE=Quicklynx;204932]The guy who put the 6 speed on his Gen II GP is njbrain. Search his name and look for his thread. I believe he listed eveything needed and posted most of the directions.

Has your friend considered a LS4 swap? It is a direct swap.

I'm guessing he mainly wants the 6 speed though, correct?[/QUOTE]

yes, he really wants the 6 speed which is cool and I don't blame him, I've swapped one into my golf recently. As for the LS4, yeah, we thought about that and weighed the options and it all came down to him not wanting a V8. Plus the 3.6L is a good combination of fuel efficencey and power. Plus variable valve timing and 24 valves really make it apealing.

Originally Posted by minichopper6hp

youre gonna need to use the g6 stuff, all the wiring and pcm. none of the 3800 parts are interchangeable and youre going to need hubs for a malibu and possibly custom length axles.

I can get the malibu parts no problem. As for wiring, you can't even get away with the 3800's fuel managment? Seems odd that you can't mix and match pieces. I know me and my boys swapped a 1.8T into a mk1 rabbit and we used mechanical injection that came with the body. I mean I'm not saying your full of it or anything but the only thing I can see losing from the engine is vvt until we get the custom loom done. Also having to flash the 3800 rom for a manual tranny.

Few other questions:
1. something I did not anticipate was how the RPM sensor drives the tach. Is it digital or analog? I'd assume it's digital running through CANBUS.
2. Will I have to get an imobilizer for the ecu to run the stock cluster?

**blueguy** · 07-07-2009

Nope he ain't full of it...the 3800 fuel system wouldn't even line up let alone fit in a 3600.

**minichopper6hp** · 07-07-2009

not to mention the different firing order, fuel requirements, everything etc, etc, you have you use all the 3.6 stuff.

**Sabrewings** · 07-07-2009

The 3800's software is expecting 3800 sensors and a true 3800. Need to use the G6's electronics.

**deathmetalscottie** · 07-07-2009

ok that was what I was affraid of ok. Pardon my ignorance, I'm learning the ins and outs of these engines. But thats ok, any engine that we get we'll be rebuilding anyway and that will give us time to build up the engine loom.

But will the engine bolt up to the mounting points? I can't find any good pictures of the G6 bay. The few pictures I did see were of the LY7 in a caddy and the bay is almost completley covered.

**deathmetalscottie** · 07-08-2009

anybody got info on the mounting points?

**copterdoctor** · 07-08-2009

Most likely you will have to build custom mounts for it (or modify the stock ones to work). The Grand Prix is a lot wider than a G6, and I'm pretty sure the mounting points are completely different.

Even all W-bodies aren't created equal... a Grand Prix has different mounting points than say a Lesabre even though they are both 3800 powered.

As a suggestion, the new Buick Lucerne I think comes with a 3.9L V6, and is a W-body vehicle.
Also the G6 GTP comes with that same 3.9L engine with a 6-speed manual in 2006. This might be a better option for you to look into. The 3.6L V6 wasn't that great.

The Lucerne Mounts might work for the 3.9L engine.

Picture of 3.6L used in G6 GXP:

Picture of 3.9L Used in G6 GTP (6speed manual) and used in Lucerne and Impala (both W-body vehicles)

Notice how the 3.9L engine mounts look almost identical to the 3800 engine mounts

**blueguy** · 07-08-2009

OOOOOOOOO, your onto something about those 3900 mounts

**deathmetalscottie** · 07-09-2009

ok now were getting somewhere. Ok, the mounts look very similar indeed which should make things similar.

One thing that I am wondering, for sh*ts and giggles, is how the 3.6 engine is not a good engine compared to the 3.9. It makes more power per liter and should have a better head design than the 3.9 (at least I would assume since the 3600 is a 24v engine and the 3900 being 12v, a better breathing head). Where is the flaw?

However, judging by how the front mounts line up so well on the 3900, this might be the better option, provided there is some aftermarket for these which I would assume there is.

**copterdoctor** · 07-09-2009

3900 Vs. 3600

The 3600 is a more powerful engine, it also isn't an engine used in the W-body Vehicles. So finding mounts that already exist for it would be close to impossible. you would have to fabricate, but seeing as how you are doing an engine swap, you where going to have to do that anyway.

The 3900 is found in both the G6 (LZ9) and many W-body vehicles, so the mounts will be easier to come across, along with many other potentially required components. This engine also has displacement on demand in Impala's and Lucern's (LZ8). Match that with a 6speed manual geared properly and you will be looking at very impressive fuel economy.

Now if you are looking at the numbers on paper....

depending on vehicle application (and tuning)
3600 V6: 252hp @ 6100rpm, 251 lb/ft torque @2300 rpm 10.2:1 compression ratio, engine weighs ~370lbs (the L67 engine weights ~390lbs)
3900 V6 (LZ9): 240hp, 240 lb/ft torque

If you want the best 3600 V6, you should probably be looking at the Cadillac CTS 3.6L . It's direct injection and might bolt up to the G6 6speed, but I'm not sure on this. It's hard to tune and get a wiring harness for it to work. I don't think the mounts will work without fabrication (RWD engine). And it's the only 3.6L still being made.

302hp @6300rpm 273 Ft/Lbs torque @ 5200rpm

**deathmetalscottie** · 07-10-2009

I think that the 3900 might be the best way to go, although the CTS engine is powerful, I'm not about to start transversally mounting a normally longitudal block. Plus it's direct injection, and FSI, DI, whatever you want to call it, I call it a pain in the ass.

20 less horses ain't bad and theyre pretty readily available on car-part.com. plus like it has been stated, it's been mounted to other widebody cars.

**copterdoctor** · 07-10-2009

now if you really wanted to do something special.... Take the entire powertrain from a new cobalt SS Turbo.

The 4 cylinder engine is light, comes with a manual gearbox, and has more power and torque than both V6's you are looking at (260hp). (the cobalt gets over 30mpg highway with that engine too)

With the weight reduction you would get by going to that engine, the car would handle amazingly well. The wide track of a grand prix with significantly less weight from a smaller gearbox and engine. It's also really easy to turn up the boost on that engine to well over 300hp. (people have done it already reliably)

**Quicklynx** · 07-10-2009

Parts for those LSJs aren't to expensive as well

I wanted to put one in my Grand Am... but too much work than I'm willing to do

**copterdoctor** · 07-10-2009

Originally Posted by Quicklynx

Parts for those LSJs aren't to expensive as well

I wanted to put one in my Grand Am... but too much work than I'm willing to do

I think that's the problem most people run into. It is a LOT of work to do an engine swap, especially from an engine that wasn't intended to be in a specific vehicle.

It was easy back in the 60's when everything was carburated, but now with Direct injection, and vehicle specific PCM's, it becomes more of a challenge.

**deathmetalscottie** · 07-11-2009

Originally Posted by copterdoctor

now if you really wanted to do something special.... Take the entire powertrain from a new cobalt SS Turbo.

The 4 cylinder engine is light, comes with a manual gearbox, and has more power and torque than both V6's you are looking at (260hp). (the cobalt gets over 30mpg highway with that engine too)

With the weight reduction you would get by going to that engine, the car would handle amazingly well. The wide track of a grand prix with significantly less weight from a smaller gearbox and engine. It's also really easy to turn up the boost on that engine to well over 300hp. (people have done it already reliably)

see yeah direct injection has made swapping new engines into older cars a pain. It's a whole different animal and especially the VW FSI engine swaps. Usually people have to swap the entire harness and I mean the ENTIRE harness to get the engine to work.

Also, I'm figuring out that GM isn't nearly as modular as VW.

Now for the cobalt swap. That would be cool to swap in an ol' Opel engine now wouldnt' it, however, there is still a mounting issue that would need to be dealt with. It is a good idea but not nearly as feasible as the 3900 swap.