So, I own a 2004 Buick LeSabre "Custom." The car is completely stock with 58k original miles. I've owned the car a little over a year now and she'* been pretty good to me, though she has her problems.

The transmission is on it'* way out, which is sad at only 58k miles. The state of the transmission has been verified, so no need to delve into this further at the moment. The car is very drivable as-is so I've been taking my time to decide how to proceed. The way I see it, I have three options:

1. Sell the car.

2. Swap the trans with a low mileage used trans. I will do the work myself.

3. Pull the motor and trans. Create a monster.

I don't really want to sell the car as it is a nice, comfortable driver. She'* also in excellent shape both inside and out. It pains me to think about going car shopping or getting another lemon. Besides, I have been looking for a project.

I know that swapping the trans with a used unit will run approximately $700. This is the cheapest option and also the least amount of fun. I know that a LeSabre isn't supposed to be fun, but I have a soft spot for Q Cars. I'd like to make this thing into a beast, if possible. A LeSabre Super.

I have been kicking around two options for engine swaps:

1. The trusty 3800 Series II L67 Supercharged V6 w/ trans. 240 HP / 310 lb·ft torque

2. The 5.3 LS4 V8 w/ trans. 303 HP / 323 lb·ft torque

If I go with the L67 then the brakes may also get an upgrade. At the very least, the calipers will be painted red. If I go V8 then the brakes will go larger and the exhaust may also get tweaked (nothing ghetto). More could also be done but I'd like to keep the stock look with minor (yet noticeable) exterior changes.

So what do you guys think? I'm no GM expert, more of a Benz guy. How difficult would each of these be and what all is involved (changes to electronics, suspension, frame mods, etc.)? I know the 3800 swap is easy but how about the LS4? Is this even possible? What brakes are compatible and what would be the best option for each? Do you know if this type of conversion has been attempted before? These are just a few of the questions that I have.

So feel free to school me on the intricacies of GMs. I need some discussion to set me on the right path.

Well, the L67 would be a direct/hassle free drop in. The block is virtually identical to your L36. Plus, it'* been done here quite a few times, even I have done it. But, your not only going to need the engine and trans, but the drive shafts, engine harness and the L67 PCM(unless you know someone with HPTuners--me)
Top swap is another option, but more involved work wise.

I'm not sure of any one upgrading to a V-8, let alone if its even possible with our frames.

But, with the amount of L67 UPGRADES, it will really put you past the power output of the V-8. Plus the WHINE of the supercharger is addicting.

https://www.gmforum.com/performance-...-298604/page2/

the l67 would be easy, been done a million times. the 5.3 was never in a h body i dont think it was a n-star. the ls4 was in the w-bodies which use a different mounting, could be easy if your good with fab i dont know but i dont remember hearing of anyone doing it to a h-body, probably cost wise it makes more sense

Yeah, I've been thinking that the L67 makes the most sense.

What kind of upgrades could I spring for on the L67 and how much power can I expect to gain? Is there a limit to what kind of power the stock frame / suspension / trans can handle?

What kind of brake and exhaust options do I have with my LeSabre? I'd like for the car to have a distinctive growl but nothing ridiculous. Something similar to what the newer V6 Infinitis get would be satisfactory.

I'd imagine that L67 PCMs and wiring harnesses are dime-a-dozen. Am I correct in my thinking? Does anyone have the part numbers?

I'll put it to you this way. A few years ago, some engineers from GM decided to spice up a 2000 Bonneville and push it past 200MPH. Of course, they did.

Here'* the article...
http://www.auto123.com/en/news/ponti...ats?artid=1303

Part #'* are going to be different from year to year. You would need to stick with something close to the year of your actual car.

Ok, so if it won't fit in an H Body frame, where did the Bonneville GXP come from?
The subframe will probably be different, but besides that, its still a Bonneville, which has most of the same pinnings as the 8th gen LeSabre.

its not that it wont fit, its not cost effective. the 8 in the gxp was a northstar which has no mods and frankly sucks for power and reliability.

according to that article the l67 made 600hp with a modified stock sc and ported and polished stock heads. to make a ls4 you are talking serious mods or a sc/turbo so it would be several thousand plus whatever it takes to install.

Yea, what Justin said.

Aint worth the effort for the POS Northstar.

There are 2 or 3 companies that cater to the 3800 Series 2 engines.
ZZPerformance | 3800 Performance Parts | Largest Aftermarket Supplier!
3800 Performance - high performance aftermarket car parts for your Grand Prix, Monte Carlo, Impala, Regal, Bonneville, and V6 F-body!!
3800 Parts | 3800 Performance Parts | 3800 Series 2 Performance Parts - W Body Store

They have all the cool parts to add on to the L67.

I wasn't saying it would be cost effective, I was just saying it was possible. The L67 is definitely a better alternative, as far as building a stout motor.
I've been considering the same swap idea, since the L36 in my 04 LeSabre is now somewhere in the 160,000 mile range. Probably would have done it by now if I hadn't bought my 4wd toy.

I think ditch the supercharger add a mildly built 4t65hd add a turbo or two throw in some L32 stock rods and you could have a 750+ crank hp monster even if you up the boost on the l67 you will need better l32 rods plus a turbo is not parasitic like your SC