Researching an LS4 swap into my '98 Buick Regal... the bad idea that is too awesome to ignore

So, my '98 Regal with a supercharged 3800 has developed a slight overheating issue. Several signs, such as the coolant being pressurized several days after the car has been stopped, suggest it's a head gasket. I'm doing a bit more testing before I tear into it, but wanted to have a backup plan if it's something worse, like a cracked block.

The obvious back-up plans would be "Get another 3800" or "Scrap it and get something else" (I paid less than $3000 for it, so this car is fairly expendable). And then there's the completely absurd idea: "LS swap it" seems to be the answer to a great many things, and the later W-bodies came with a LS4. There's usually a few wrecked examples on Copart...

However, I haven't found very many reports of it being successfully swapped into earlier W-bodies, except one thread where this guy suggested you could just drop out the subframe from a donor car and bolt it in, but would then be left with a number of wiring questions to solve. Most discussions seemed to have been "Don't bother, it's too much work" without specifying what sort of work. Anyone know of better write ups? Or convincing arguments for or against this?

I'm not exactly sold on the idea, and wouldn't want to do that if the 3800 just needs a new head gasket. But it does have me wondering.

If you want a front wheel drive ls motor, sell the regal and buy a later car with it from the factory.

Pretty much the only transmission that works with the LS4, due to the starter, is the one that came with it. That is the heart of the problem with swapping.

oldopelguy said:

Pretty much the only transmission that works with the LS4, due to the starter, is the one that came with it. That is the heart of the problem with swapping.

And said transmission isn't exactly happy about dealing with the amount of power the LS4 puts out. 

Wiring is similar to any other swap.  What should happen is you get the c100 pinout for your car and your donor and make the connections there and you’re on your way.  On a W body the c100 is the one that mates the engine harness to the body harness through the firewall.  I’m not sure about the cradle interchange or mount situation.  I would try, then again i would say get two donors and put one in the trunk too.  606hp awd burnouts sound fun.  The ls4 is a cam and intake away from a transmisison exploding 400hp.  It already has the ls6 243 heads(minus the sodium filled valves) and the intake really chokes down after the already pretty small throttle body.  

Go find a crashed impala SS? Not sure of the interchange but that gets you a transvers 5.3 ls I think. 

pimpm3 said:

If you want a front wheel drive ls motor, sell the regal and buy a later car with it from the factory.

What kind of a GRM answer is that!?

get the berk out!!  :-)

I'd just build a 3800 up and be done with it. Great engine. 

In reply to MadScientistMatt :

If you have a blown hg or cracked block why would that cause the radiator to hold pressure for several days? Wouldn't the pressure just push coolant into the cylinder or crankcase?

It does seem like a lot of work, esp. when the 3800 can make a whole boatload of power with more boost anyway.  

That said, there is a guy on the Saturn forums who shoved an LS4/F23 combo in a base model SL and its silly and I love it.

In reply to A 401 CJ :

I am all for weird swaps but in this case I think cutting bait is the best option.

gearheadmb said:

In reply to MadScientistMatt :

If you have a blown hg or cracked block why would that cause the radiator to hold pressure for several days? Wouldn't the pressure just push coolant into the cylinder or crankcase?

While I'm all for oddballs swaps, I was going to post this exact same question. I suspect you have something simpler/cheaper going on, like a clogged radiator. I suggest some simple diagnosis before deciding a swap is the only choice, unless of course you're just using the above as an enabling excuse, then go for it.

I think I'd get the Grand Prix version if I wanted a V8 W-body as I believe the Pontiac got more changes than the Chevy when they put that motor into that chassis.  

Fixing the V6 you have probably makes the most sense.  Putting a V8 in the W-body always seemed like a good way to make the platform actually worse.  But that's just my take on things.

ProDarwin said:

It does seem like a lot of work, esp. when the 3800 can make a whole boatload of power with more boost anyway.  

That said, there is a guy on the Saturn forums who shoved an LS4/F23 combo in a base model SL and its silly and I love it.

This one? 

When it comes to swaps, the weirder the better.  But if you use an LS engine, you're pretty much surrendering your "weird" card from the get-go.

OK, some more testing on the 3800. I've got 160 psi of compression on all the cylinders except #4, which has 120 psi, and #6,  where I quit testing because it's at the back of the motor, a pain to reach, and I've already established that back cylinder head needs to come off.

And the radiator had just been replaced by a shop that clearly hadn't done a compression test first. I had been thinking, "I don't have time to deal with this myself," but I have even less time to deal with incompetent paid parts swappers.

My main plan is to repair the 3800. Just pondering what to do in the unlikely event that the engine is damaged beyond repair. And... this is a big question mark as a swap. It seems as if both the pros and the cons here are "GM has already built almost the exact same thing." The marginal transmission is a definite minus, and putting a manual transmission behind it would add way too much cost and time.

I was thinking a driveline swap from one of these

https://hartford.craigslist.org/cto/d/2006-chevy-impala/6511258064.html

The 5.3 LS4 just isn't that good of an engine. Unless you are hung up on having a V8 soundtrack, I'd not bother with it. It doesn't make that much power, in fact, the base 3.6L V6 in the last of the W-body Impalas made more power, and with a 6-speed auto, I believe was actually faster. It has the same Active Fuel Management cam and lifter issues as the truck engines. And if you think it's a pain to reach the sparkplugs on the 3.8L, wait until you shoehorn the LS4 in there. They are a pain to work on. And they are backed by a dodgy transmission. A tweaked 3.8L can make just as much power, and more, as an LS4 for less money, while being easier to work on.

So is there any manual fwd transmission that easily bolts to an LS? 

In reply to Tom Suddard :

None that I'm aware of. I met a guy who manual-swapped a 3800S/C, but it involved some serious jiggery-pokery. He was using a Z34 Lumina manual transmission, which was only available for a few years as an option. And there are no rebuild parts for that transmission, so he ended up having to hunt down three of them to piece them all together to make one that had synchros that were good. Then he wiped a clutch and slave cylinder out and had to adapt a 3000GT VR-4 slave cylinder, because, surprise, the Lumina slave is no longer available. Neither is the 3000GT slave, so that was some new-old stock part he found. Clutch was used out of a Lumina as well, and he said it was slipping and NLA, so he was going to have to hunt down another.

In reply to NickD :

Doesn't surprise me one bit that the last W-body with the 3.6 VVT was faster than the LS4.  That's the fastest rental car I've ever had...and I've had a bunch including twin turbo Infinity Q somethings.  

Last one I had would break a front tire loose on an on ramp if floored from 50.  Granted, I've had others with the same powertrain that weren't as peppy but that's one heck of a base model grocery getter.

In reply to A 401 CJ :

Indeed. When the '12s first came out, I wasn't aware that they had replaced the old 3500/3900 with the 3.6L. Went out for a drive in a customers, punched it to get up to speed and went "What the hell is under the hood of this thing?" Pulled over and saw the 3.6L tucked up in there. I know that we were sending techs down to New York City for training, and they kept grabbing the Impalas out our rental because they could haul ass there and back and no one would notice them.

Tom Suddard said:

So is there any manual fwd transmission that easily bolts to an LS? 

The GM F40 was used behind (beside?) the LS4 in some applications.  If we were talking about a rear mount LS4/F40 swap I'd be excited about that but just sticking an LS in in place of the 3800 seems like a lot of work for what you end up with.

I don't believe the F40 six speed was paired with the LS4 in a factory application. It can be done, but needs some fabrication. It is, however, apparently pretty straightforward to put it behind a 3800...

what about the Getrag manual trans from the fiero's? there were a few of them that were decently strong and can probably be used in a fwd car.