New G body owner - '85 GP

[FL85GrandPrix]

Yes, underside is spotless. It's a FLORIDA car!! Zero rust.

 

[UNGN]

If you keep the 2.40 gears you'll need a loose lockup converter with any performance motor, but thanks to turbo buicks, these are pretty plentiful for the 200R4. With a low end torque motor build, you might even get away with a factory turbo car D5 converter (2400 stall) on street. These can be had pretty cheap.

You'll probably want 3.42 gears or better if you want it to feel "peppy" however.

With 2.50's gears, our 2+2 only ran 14 second 1/4's but would run away from low 12 second C5 ZO6 above 100 mph (and they never would catch us). Even 560 lbft of torque has a tough time overcoming the mechanical disadvantage.

 

[FL85GrandPrix]

The 2.XX gear is a goner. I've built a lot of axles on the truck side. the K5 in the background, I just got done rebuilding the front end. Stock 3.42 gears, TruTrac Diff, 28 spline Yukon shafts. I've also done some straight axle swaps in Toyota IFS trucks. So building the rear axle is not an issue. I was thinking I want a 3.73 R&P. Hit the strip and drive it home on the highway. If I kept the stock 7.5 axle I was going to do the F-body disc brake conversion, Yukon shafts, 3.73 gear and a clutch type LSD from Eaton. But after seeing how weak the 7.5 is I'm not sure I want to spend the money on it. for about $2k I can get a drop-in Ford 9" kit and have it built my way. Moser also makes a drop in axle you can build to spec. Not sure how much theirs is. But I figure for $2k-ish I should be able to find a nice drop-in axle that is much beefier than stock and will have it ordered with discs. THe 9" kit I found also lets you spec your wheel pattern, b/c I really want to keep the factory bolt pattern if possible.


All this motor and axle talk on the forum and I don't see much chatter about the stock driveshaft between the 200R4 and the 7.5 axle. How much will that #2 pencil handle?

 

[Texas82GP]

Beautiful car! Great find! Congratulations! I went with a 350hp 350 from Pace Performance for my car. It's all new and cost less than $3000. Here's a link to my thread if you are interested......
https://gbodyforum.com/threads/space-city-1982-gp-build.55501/
I wish my car was as nice as yours. Welcome to the site from Houston.

 

[Dinosport]

Super nice car. Love those GP's. They have like a classy sporty look. And welcome to the site. I've learned a lot on here. Anyway as for motor swap sky's the limit. Really depends what type of performance you want, how much you want to spend, and how much work your willing to put into it. You don't really have to cut up anything as far as I know for any gm small block including an ls swap. They make adaptor mounts that just bolt right up. ls swap is more work for sure but really nice power, fuel mileage and reliability combo. But a good old school small block built right will get the job done and sound phenomenal.
Good luck with it.

 

[FL85GrandPrix]

Been doing a lot of reading. Pretty sold on a L31 96-99 5.7L truck motor with vortec heads. Cam, intake manifold and 4 barrel.

 

[Opie Knievel]

Been doing a lot of reading. Pretty sold on a L31 96-99 5.7L truck motor with vortec heads. Cam, intake manifold and 4 barrel.

That's a hard combo to beat for the 350-400 hp range.

 

[FL85GrandPrix]

350-400 is the target. And i want a real muscle car sound.

 

[FL85GrandPrix]

And ishould be able to reuse the serp belt setup too. I will look for a complete motor with accys.

Stick with the 200r4. Swap it for a built version.

Moser axle with 3.73 lsd.

 

[Opie Knievel]

Do some research on the valve springs. That's the only thing that limits a stock vortec head. There are a few different ways to address this problem. Factory springs are only good for about .460 lift.