79 Firebird Project - GN drivetrain swap

[SolarGoldRaptor]

Hello guys,

Since my '79 Firebird project is going on the long run, with a lot of metal work involved, I want to make it the way I want.
So my plan is to swap the N/A 3.8L V6/TH350/2.56 non-posi for a complete 86-87 GN drivetrain. I have the Turbo hood, the Turbo wheels will come.
The problem is I don't know what is required apart from the obvious :
- engine/radiator/intercooler
- transmission (maybe a TH350 would work?)
- computer
- engine harness

So what about those :
- rear end ? what ratio ? posi ?
- dashboard harness ?
- engine mounts ?

Anything I'm forgetting ?

Thanks !

 

[charlief1]

Welcome back. Been wondering if you had disappeared into the net never to be heard from again. I moved you to the general section for better input from others. You might want to visit the hybred forum as well for some idea of what you'll need to do.

 

[Steve]

I just got done installing a LC2 into a 67 Firebird. You wont need to make any alterations to the dash harness, you will only need an engine harness for the Lc2. I used a stock harness and modified it and removed everything I did not need(emissions etc). I used a turbo 400 with a Gearvendors overdrive in my conversion but the th350 you mentioned will work although you wont have overdrive and the th350 will need some mods to handle the tourque of a LC2 if your motor is more than stock and if you drive it hard. I used a 3.23 gear in my car but you could use a 3.42 if you want which is what turbo Buicks had from the factory and what most people stay with. I made my own mounts. I got the ideas for the mounts from Turboindian here on the board that also has a 67 Firebird with a turbo Buick motor. I took the ideas from TurboIndian then just made them work! I moved the motor all the way back as close as I could get it to the firewall for the best weight distrubution I could get. I used a regular 3 row radiator for a 400 Firebird and made my own hard pipes for the radiator hoses. The link below has pics of my conversion.

http://www.turbobuick.com/forums/tu...ary/321459-my-67-firebird-turbo-buick-v6.html

 

[Fast4Ward]

pretty straight forward swap for the most part. use the gn fram pads...there is enough holes to mount them but you may end up welding a section.
here's a fellow canuck, he's really easy to talk to. send him an email...i have i think his name was Marc or Mike...i've got his email address somewhere. have a look.
1981 Turbo "GN" Trans Am going under the knife - TurboBuicks.com
Marcs muscle car site

 

[Fast4Ward]

did i read that right ...your going NA?

 

[Nick Micale]

A couple years ago we did an '87 GN drivetrain into a 1981 turbo Trans Am.

There were 2 major issues, first with the downpipe, and second with the AC,alt/PS bracket.

There is just NOT a good path to install the downpipe. Our remedy was to remove the AC box and components from the firewall to make room for it.

The AC compressor will interfere with the upper control arm.

Since the customer wanted to maintain AC in the car we installed a Vintage Air system and fabricated a bracket assembly for the new compressor, alt and PS pump. Worked out real nice.

We used a GN trans and 3.73 rear end gears for a nice cruiser.

A new fuel tank for an '81 Firebird was purchased and we fit a GN hanger and fuel pump which worked well.

This project cost well north of $20K, and took over a year with a TON of smaller "issues" to integrate all systems for a reliable driver. :biggrin:

P.S. The second pic shows the stock AC bracket in mock up to show how the compressor, and also downpipe, will NOT fit!

 

[Nick Micale]

Guess I should add info about the computer and dash wiring.

Basically, the Trans Am wiring for the dash was retained, but we had to replace the stock gauges to work with the Buick engine. We located similar gauges to replace the originals, but kept the same look.

The funky lights in the hood for boost indicators were replaced with a boost gauge in the original housing.

The installation of a FAST XFI computer with a customized stand-alone harness made a very neat and clean installation.

Engine mounts were very simple brackets we fabricated when the mock-up engine and trans were set in the car for proper location and alignment.

 

[SolarGoldRaptor]

Wow, thanks for the great input guys.

I didn't come back earlier because I bought a 1984 Trans Am HO 5 speed last year and she's the one I've been busy working on since then.

I'm keeping the engine stock, 240hp is well enough for my use. I hope to find a good running engine and transmission that won't need any big work. I will have to import it since there is absolutely no way I can find one here.

The '79 doesn't have AC so it shouldn't be a problem, it's an Esprit with only a very few options : side stripes, A/T, rear defrost and power trunk. All the rest is standard Esprit stuff. I've got plenty of room in the engine bay.

So the old 3.8L LD5 engine mounts won't work for the LC2 ?

 

[charlief1]

The mounts should work but be prepaired to do some minor mods to them. I don't think you'll have to many problems except for the down pipe since you aren't going to have AC in the car.