Thread: Whole engine block kinda Swap

Background: My friend just got into some problems with his GP and decided he could no longer handle it because it would cost too much to fix for him. He's a student in college and so am I but I have a little more money to work with. He wants to sell me his '98 GP (same year as mine coincidentally) My car is a 2-dr 3800 series II coupe and his a 4-dr sedan Series II with a supercharger on it. Now, I'm a little tempted to want to do a top swap. After reading these forums, that appears to be a bad idea. Now his chassis in the back is in really bad shape and a mechanic quoted him more than he can afford, which is why he wants to sell me the car. Now for the question.

Rundown of facts:
CAR1: 98 Grand Prix GT 3.8 L L36 coupe
CAR2: 98 Grand Prix GTP 3.8L L67

Can I do a swap of the engine, tranny, ECM and the engine block pretty much (the least connections possible on the outside of the block is my goal, which is why I want the engine, tranny and ECM together)?

Is this feasible?

Complicated as doing a top-swap, or just a job that requires 2 good lifts and a wiring harness adapter?

Thanks in advance.

Originally Posted by Bio248

a top swap is easier than swapping the entire engine/tranny/wiring.

why do you think a top swap is a bad idea? what gave you that idea?

Just reading over the material. How hard would it be to swap out the whole thing though? I'm sure his engine and tranny are better than mine, that's really why I'm even considering it. He only had 68K original miles, my coupe is topping 180K and I don't think the tranny can handle the top swap. As stated in the sticky earlier. I also am thinking that an already assembled setup is much easier than assembling it.

Lastly, I'm not doing this myself, I'm going to get my mechanic to do it for me, so he can put them both on the lift and do whatever, that isn't an issue.

Originally Posted by 01GTP

Dont mod anything if you are not going to do the work yourself.

Well I'm not exactly mechanically inclined. I'm good at doing tune-ups. Oil changes, brakes, and rotors but anything to do past that I kinda don't trust myself.

Originally Posted by Bio248

if anything, just swap the motor only. you want the gearing in your transmission. swap the hd-diff from the trans in the other car. the non-hd should hold up fine so long as its already not failing and they are also a bunch cheaper to buy another one.

Hmmm. I'm kinda curious as to why you think it's a better idea just to swap the motor, any reason? His tranny, and motor are stronger, and relatively newer. Also if I swap just the motor, I'll still need to upgrade the PCM and get all those other parts needed for the top swap no?

Originally Posted by Bio248

here are the reasons why you dont want to swap everything:

1) the transmission you currently have has better gear ratios, the 2.93s in the hd-transmission suck

2) the non-hd transmission can take as much abuse as the hd can so long as its taken care of

3) if you do decide to have the whole motor, the compression ratio is lower meaning out of boost the car drives like a complete dog. i HATED the l67 block after i had an l36 block in my car

4) you dont need to swap PCMs, but just to get a tune so it knows what motor youre using. you can do the same with the trans file.


therefore, i suggest you only use the motor if you want to use complete parts. if you want to swap everything over, then so be it. nothing on any of the components is stronger than any other part as long as the motors/transmissions are taken care of.

Wow, I didn't know that (any of it).

#3: really? I would have thought it would get less MPG and perform a little better but that Supercharger must really slow it down. If I just do the motor swap I'm guessing that will probably be cheaper than getting the entire tranny swapped too. I read that once the engine is supercharged it needs a wiring harness adapter will this still be the case if the entire motor is changed? (this is where my mechanically disinclined mind comes in)

I have one last question if you know. What is the time difference you think between swapping the motor and swapping out everything?

My engine and tranny are both starting to show signs of wear that's really my problem. Once again why I am thinking of taking out the whole thing. Recently, when it got really cold, after driving my car for a an hour, I went to put it in reverse and it slipped. Thats not the first time, but this time it was a big slip. I could actually feel it. I just love my baby so much I wanna keep him, or at least the general body.

Originally Posted by Bio248

if your stuff is ready to take a dump then i would swap the motor and trans in then. i would keep your wiring harness, but buy the ZZP L67 swap kit (comes with a couple connectors that youll need). if you dont swap in the l67 pcm then youll need to get the car tuned for an l67 motor/trans.

I has been ready to take a dump for a while, kinda been babying it and taking it out of the city only when needed.

So you think it's a good idea to just put the trans and motor in and leave the harness. (with a swap kit of course, ZZP L67 swap kit) Thanks. Thank you a lot, I just needed someone to talk to and throw a few questions back and forth. Have a good night, and Hopefully if someone has the same issue they will find this info useful as you've given me so much to think about. I'm eternally grateful!