🔧 BUILD Turbo 3800 T56 Swapped G-body Grand Prix w/ Holley EFI

General Information

So after joining a long time ago, I thought I'd reenter with a build thread!

The car is my 1982 Pontiac Grand Prix Brougham.

Index for people who hate long threads like me:
First time running:


Finally fixed the 4000rpm breakup

T5 Carnage/4l60e swap

Power tour 2018 Mad rush to get done:

Rear Disc brakes swap/axle shenanigans

Power Tour 2019 Prep:

Glamor shots before power tour 19:

2020 quick trip

L67 short block swap and PNP:

2021 Power Tour Prep and T56 Swap:

New Wheels Before Power Tour 2021!

Late 2021 Season Refresh: Bigger Turbo, Ford 9", 1.9 rockers and little fixes:

2022 Updates: Cam swap, next engine, twin disc Monster clutch, Holley Terminator X conversion:

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It originally had a Buick 4.1 liter V6 from the factory with a 350 transmission behind it. Back in high school we thought it'd be a good idea to swap an L27 into it since we had it lying around and thought it'd be cheap quick. Anything was better than the knocking 4.1 with only 130hp though. We ended up using a 700r4 as the transmission, but the transmission never played nicely despite our best efforts to fix it. The engine was shoehorned under the hood too so I gave up on it and it has been just sitting around until now. It was a silly idea and I'm glad to be getting rid of it.

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Now I finally have plans for the car. I acquired a donor car for the whole drivetrain and am getting ready to go to town.

The donor car is 1998 Camaro with an L36 3800 and a world class Tremec T5 transmission. The car has only 112,000 miles on it and it was totaled in a front end collision. The plan is to pull everything out of the Camaro and retrofit basically everything I can into the Grand Prix. Electronically and as far as the engine and transmission go, it will be a 1998 Camaro. It's getting the engine and transmission (obviously), the PCM, BCM, and basically everything else I can stuff into the Grand Prix while still maintaining its appearance (RKE, RAP, newer chime module, etc.). Everything should have no problem playing nicely and I should be able to reuse my motor mounts, transmission mounts, and also my current driveshaft AFAIK. The Camaro is likely to be parted out afterwards.
Most current pics I've taken:

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The main highlight of the build however is the turbo!

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This is a Holset HX35. I'm not going for a huge crazy build, but I'm shooting for somewhere around 400 hp with it. The holset should do pretty well with these goals, but I'm considering switching to a HY35 exhaust housing over the twin scroll housing.
We're looking at fabbing up our own manifolds for this and going with a 3" exhaust after the turbo. Also going to be using a 3" intercooler.

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The exterior of the car will stay basically stock including the vinyl top. Sleepers ftw :fy:

Other plans include stiffer sway bars, better shocks, and lowering springs front and rear for about a 1.5" - 2" drop. I'm also going to take the body off the frame so we can add more frame bracing since these frames are pretty flimsy from the factory. Also using 16 x 8 IROC Camaro rims for now with probably 245/50-16 tires for now. I might go wider in the rear though.
I've also got an 8.5" axle from an A-body Olds for it. It looks like it'll need quite a bit of work, but I also have a few different sets of ring/pinion gears for it. I'll probably stick with the 3.73 set. The axle supposedly doesn't use c-clips to hold the axles in, but I think that whatever is supposed to hold them in is missing. It'll also need at least a new passenger side axle since the previous owner drilled larger studs in. It currently has disc brake rotors on it, and also caliper mounting brackets that supposedly fit "metric gm" calipers, but I really have no idea what will fit it. In the meantime though I'll use my 7.5" for now with the disc brakes from the Camaro until the 7.5" breaks.

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Any idea what these brakes are from?

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I know most people with these cars are obsessed with carbureted V8's, but I feel like I've made the right choice here. The V6 will be much lighter than a V8 especially with a manual transmission. This will help to remove extra weight from the front of the car and bring it closer to a 50/50 weight ratio. It'll also offer a ton of power and still give great fuel economy. Not to mention I can also tune it with my laptop! I suppose the idea is it's basically a Pontiac Grand National but with the more modern 3.8, more power, and a manual transmission.

The biggest challenge will be getting the turbo in here, and also getting the manual transmission into the car. Luckily the T5 uses a hydraulic clutch so clutch fork geometry won't be an issue. I'm still a little bit hesitant about cutting up my floorboards for the shifter though. It's looking like I will also have to do something about the seats since the shifter will sit where the middle seat is at. We'll see about using a center console... Those bridges will be crossed when we come to them though.

The first challenge was transporting the car over to my brother's house where there's a garage I can work on this in. I originally tried to just drive it out there, but the engine pretty much said "fuck this, I'm done". After a long night, we ended up trailer-ing it the next day.

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Here it is finally in the garage last night:

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yeah, it's dark. my bad.

Progress!

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front clip removed:

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engine removed:

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I'm powered by Rockstar!

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So much room for activities!!!

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So basically all of the remains of the L27 are gone. I have also started to separate the body from the frame. I got all of the body mounts disconnected, but called it quits after attempting to remove the rear bumper. Hopefully I can get the body off the frame tomorrow and get started on removing the engine and transmission from the Camaro. I've got a long road ahead of me, but I'll have this done for the Woodward Dream Cruise I'm sure.

Thanks for reading!

Mr_Roboto

Doing the jobs nobody wants to
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Feb 4, 2012
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Hey, I don't know if you have thought about swapping the front brakes from the Camaro over to your GP. I would consider it, as it's not too hard. Check out the later pages of my Pontiac build. I'm doing it on a Lemans but overall it should be very close. You'll need a different set of brackets and to cut the ears off your spindles but no biggie there. You may need to drill and tap a few bolt holes too. It's still an awesome upgrade for what you're doing though. A clean "G" car is definitely on my to do list, keep it up!
 

bs009

Making 3800's Great Again
Feb 13, 2014
698
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NashVegas
Thanks a lot everyone!


Awesome build. My mom had an 83 gp brougham that was a total lemon but it looked cool :rofl:

My dad still has it tucked away for some reason. Hasn't run in years.

Must be a trend lol. This one had to have been a lemon from the factory. It only has 68,000 miles on it and it never ran right. The engine was rebuilt before I acquired the car and it started knocking afterward.
 

bs009

Making 3800's Great Again
Feb 13, 2014
698
2,129
NashVegas
Hey, I don't know if you have thought about swapping the front brakes from the Camaro over to your GP. I would consider it, as it's not too hard. Check out the later pages of my Pontiac build. I'm doing it on a Lemans but overall it should be very close. You'll need a different set of brackets and to cut the ears off your spindles but no biggie there. You may need to drill and tap a few bolt holes too. It's still an awesome upgrade for what you're doing though. A clean "G" car is definitely on my to do list, keep it up!

It's crossed my mind at one point. I know someone makes brackets for them for g-bodies, but it also requires using the old rotors as spacers. From what I understand the brackets are hard to find though and pretty expensive
 

bs009

Making 3800's Great Again
Feb 13, 2014
698
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NashVegas
So I've never actually removed a frame from a car before...
That being said, this went really well lol.

The trickiest part was getting the body high enough so that I could roll the frame out underneath it. In hindsight I should've used casters on the wheels to roll it out from the side of the car. At least that'll be a good way of lining it up properly though when it's time to put them back together.

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Looks like my car has been hiding a dirty little secret...

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after a few trips to home depot I finally had enough wood to get it up

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So here's the plan right now. I'm sure I'll learn more down the road of other things I should be doing, but here's the main things I'm planning on doing:

That's the frame rail that runs underneath the body under the doors. It's currently a c-channel and it is extremely flimsy.. The plan is to box it.

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Planning on adding various braces back here too for all of the axle mounts. Every little bit helps on these frames.


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lower control arm mount points. These are getting braced too.

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rear frame bumper points are getting tied together. I hear these things need additional bracing even though the bumper is there. I'll also be adding a rear sway bar back here. I'm looking into trying to find a cheap option over the hellwig pro-touring bar.

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Front frame horns are getting braced to the crossmember.

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More activity space!!

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original body mounts. Not too bad

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obligatory engine bay/frame is gone pic! :banana:

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Mr_Roboto

Doing the jobs nobody wants to
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Feb 4, 2012
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It's crossed my mind at one point. I know someone makes brackets for them for g-bodies, but it also requires using the old rotors as spacers. From what I understand the brackets are hard to find though and pretty expensive

The brackets should be about $60-80. You have to cut down the old rotors, I had Wolfe do mine. It was around $60. You need the rotors, calipers and abutements. I had to upgrade my wheel studs to 1/2, I don't know if your hubs will have 12mm or 1/2 wheel studs in them already that are adequately long. The ones I used were from a 93 4WD Dakota. You can also swap in some Blazer spindles and there's a different set of brackets but it may eliminate the need for machining. Not sure.

You should also be able to offload the assemblies to an LT1 guy if you really want to for a few hundro. It's a super common upgrade to drop the whole spindle and all into an LT-1 car for better brakes.

12" LS1 conversion bracket, '82-92 F Body
 
Nice build. I would say if you wanted to since your this far into it, I would strip the frame and get it powder coated. And rhino line the bottom of the body. And I would watch with that turbo on that 3800. I've seen a lot of them pop after 15 Lb of boost when they are all stock internals. But yea nice build. Hope it works out for you and meets your expectations.
 

bs009

Making 3800's Great Again
Feb 13, 2014
698
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NashVegas
The brackets should be about $60-80. You have to cut down the old rotors, I had Wolfe do mine. It was around $60. You need the rotors, calipers and abutements. I had to upgrade my wheel studs to 1/2, I don't know if your hubs will have 12mm or 1/2 wheel studs in them already that are adequately long. The ones I used were from a 93 4WD Dakota. You can also swap in some Blazer spindles and there's a different set of brackets but it may eliminate the need for machining. Not sure.

You should also be able to offload the assemblies to an LT1 guy if you really want to for a few hundro. It's a super common upgrade to drop the whole spindle and all into an LT-1 car for better brakes.

12" LS1 conversion bracket, '82-92 F Body

Thanks for the link! I'll have to think about it. It'd be weird to have the camaro discs in the rear and the stock g-body 10.5's up front. I'll probably see if I can find a way to make my own mount and swap them over.
 

bs009

Making 3800's Great Again
Feb 13, 2014
698
2,129
NashVegas
Nice build. I would say if you wanted to since your this far into it, I would strip the frame and get it powder coated. And rhino line the bottom of the body. And I would watch with that turbo on that 3800. I've seen a lot of them pop after 15 Lb of boost when they are all stock internals. But yea nice build. Hope it works out for you and meets your expectations.

Thanks! powdercoating is out of the budget at the moment, but I am going to be using POR15 on as much of it as I can. I'll look into some sort of bedliner for the body then; I'm sure it could use it.

As for the L36, I've heard of a lot of people that have good luck with them. They're not too much different than the L67 and the L67 is much stronger than it needs to be. It does have a higher compression ratio though so I'm sure it won't need all that much boost. The plan is to start it at around 10 psi and play with the boost controller to see how much more it has left in it.

The rear end will go first though before I have enough power to damage the engine. The transmission will go second, and then maybe the engine will go. lol. I'm not scared about the engine at all at this point.
This will be the budget build. After I break something and I'm out of college it will get worked over again with a stronger transmission, a stronger rear end, and a second turbo :D
 

1quick

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i wouldnt worry about the l36, ive had two l26's (the weekest 3800) and pushed them over 500whp in a grand prix one of them had a cam and double roller 130# valvesprings and every other part was stock in the long block including the head gaskets and head bolts 17psi almost every day for a whole summer
 

bs009

Making 3800's Great Again
Feb 13, 2014
698
2,129
NashVegas
I pulled the drivetrain from the Camaro yesterday. What a PITA. I probably snapped at least 20% of the bolts on that thing because they were so rusted. I'm so glad I don't have to work on one of these regularly! I don't know how they fit turbos in here or even the LS1.

Disassembly:

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Aaaand it's out!

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Engine hoist was extremely helpful here!

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I never really noticed how much the shifter was tilted over until I got it out of the car. Hopefully it fits well enough in the Grand Prix.

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Camaro engine mounts. These things are huge!

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Mockup of drivetrain on GP frame:

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Transmission and crossmember:



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Looks like the driver side engine mount will fit pretty well. Looks like I'll have to grind down the edge of it though for the engine oil dipstick to clear.
The passenger side is a different story though because the block has this tab sort of thing on it above the bolt hole on the right.

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Looks like I'll have to figure something else out for that side.

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length looks like it'll be close. I won't know for sure until I get the exhaust manifolds off it though since they don't clear the front suspension.

It looks like I'll also have to find a spot to relocate the A/C compressor to if I want to keep A/C. I'll probably end up leaving it out. Thankfully it looks like those 2 are the only issues right now. It looks like I'm in business!

The engine is going to stay mostly stock for now. I'm planning on replacing the intake gaskets and the oil pan gasket so I can get a good look at the motor. I'll also end up porting and polishing the intake I'm sure too. It'll definitely be getting a cam down the line too.

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Camaro sort of back together:

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I hate disassembly so I'm glad I got all that knocked out this weekend.
This is where the actual building of the car starts!! As for now though, I'm wiped out.
 
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