🔧 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

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I was gonna say I'd swap those out first. Low numerical like that will load back into the powertrain and make that converter slip more than say 3.42s probably.

I know that "good" G-body axles are getting hard to come by these days though.

If you're looking for something to get parts from an Astro Van uses a 1350 rear yoke and 3.42s almost grow on trees in them. If you've just got a howl and everything turns freely/nothing looks burnt or work unevenly there's a good chance it's just loud. I had one in my Astro that was like that, ran it for 40Kish that way before the 9 inch went in.

Also as a kludge to get you by hy-tran (J20C) works wonders in auto transmissions. It won't keep it alive forever but it'd probably buy you some time if you need it.
 

bs009

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Here's some screenshots from one of the videos I made a while back. The axle is buried right now so I haven't had time to pull it out yet and get real pictures:

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Next weekend I'm planning on taking the turbo parts off of the car to see if there's interest in it as just a regular running driving car with a 3800 and no turbo. I'll just need to make an exhaust system for it NA. I'm also going to swap torque converters to see if that fixes the trans issues. If not I have a spare I can throw in.
There hasn't been a ton of interest in the car yet so maybe it will be more appealing as a running/driving car without the turbo parts.
 

v6buicks

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'88s are the best to get from my understanding. I'll be sad to see you going away from the longitudinal setup, but Fiero swaps are cool too! I have no room to talk though. I still want a LeSabre GN or T-type. Therefore, I agree. YOLO! Life's too short to not buy an affordable car that you've always wanted.
 

bs009

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That's kind of what I'm thinking too lol.
I'll also be sad to get away from the longitudinal setup too, I've been really hoping to do a t56 build with an IRS someday, but that could still happen down the road when I'm a little more stable financially.

If it really is rust free it seems like a pretty decent deal. It's an 84 with quite a bit done to it. I'll want to do a drivetrain swap down the road, but this seems like it'd be a really good base to start from
 
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bs009

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I'm not a Fiero aficionado, but an '84 fastback? I didn't think that was a thing. It sounds pretty cool though. I actually slightly prefer the older style Fiero styling over the face-lifted.
You're right they didn't have it in 84, but this one would have the body panels swapped on and then the 88 suspension swapped over too.
I'm a huge fan of the fastback over the notchback myself lol
 

Pewter-Camaro

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'88s are the best to get from my understanding. I'll be sad to see you going away from the longitudinal setup, but Fiero swaps are cool too! I have no room to talk though. I still want a LeSabre GN or T-type. Therefore, I agree. YOLO! Life's too short to not buy an affordable car that you've always wanted.

Sorry for going off topic but.... what!! I thought I’d be the only one ever to want a LeSabre T-type or LeSabre GN! My first car was a 2 door 87 LeSabre and always wanted a t-type. Always loved how the hoods opened on those cars Too.
 
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v6buicks

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Sorry for going off topic but.... what!! I thought I’d be the only one ever to want a LeSabre T-type or LeSabre GN! My first car was a 2 door 87 LeSabre and always wanted a t-type. Always loved how the hoods opened on those cars Too.
Haha nope! I've always loved the way they looked and rode. I think an LGN would be a mind f*** sitting next to my '86 Regal GN, but I can never get myself to buy one. The looks just haven't outweighed the lack of balls under the hood and difficulty to modify. Sadly, they're also starting to get pricey. There was an LGN for sale in Alsip in December. I tried to get him to trade for the Camaro, but no dice.
 
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Pewter-Camaro

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Haha nope! I've always loved the way they looked and rode. I think an LGN would be mind f*** sitting next to my '86 Regal GN, but can never get myself to buy one. The looks just haven't outweighed the lack of balls under the hood and difficulty to modify. Sadly, they're also starting to get pricey. There was an LGN for sale in Alsip in December. I tried to get him to trade for the Camaro, but no dice.

yeah they are not fast or even mildly decent handling and the old 440-t4 trans was weak as shit.
The 87 LeSabre I had just cracked into the 14’s with 75hp shot of spray and broke transmissions often. Ion the memories... I may have to find me a LeSabre T for a fun car. Those show up now and then for decent prices.
 
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bs009

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Sorry for going off topic but.... what!! I thought I’d be the only one ever to want a LeSabre T-type or LeSabre GN! My first car was a 2 door 87 LeSabre and always wanted a t-type. Always loved how the hoods opened on those cars Too.
You guys would both get along with my brother Mattstrike Mattstrike :ROFLMAO:
He has a t-type and had a l67 swapped 86 Lesabre
 

Jfrost

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Fiero’s are a blast with a 3.8 in them. Biggest thing with Fiero’s is finding one with a rust free spaceframe, or as little rust as possible. Easy please to check is rear fender wells along the frame rail. If there is significant rust there I’d pass as it will only get worse the more you peel back.

Unique to the 84 as well is the wiring and routing to the engine bay. If the owner took the time to swap over fastback panels and an 88 suspension, maybe they did so with the wiring too. What engine is in it? If it’s the V-6 then they either swapped the harness or frankensteined the original. I’d get a list of all that was done to the car.

As someone already pointed out, doing a 3.8 swap in an 88 or one swapped to an 88, require different engine mounts as well as exhaust considerations with the different shape of the subframe.

Were the undercar coolant tubes changed as well? I would assume so and that also requires different consideration for the coolant/heater hose routing.

Lots more to be considered but seeing your skills from this thread, the Fiero swap shouldn’t be an issue.

Let me know any other questions you have, also check out my build thread as that could answer some questions too.

 

bs009

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thanks! all good info there, I'll be sure to keep my eyes peeled looking at this thing. I've got no problem walking away from it and dragging the GP back home if I have to lol.

The one I'm looking at currently has a DOHC 3.4 in it right now being run off of megasquirt. it has the Isuzu trans too so it's not the most ideal drivetrain, but it might still be pretty fun as it is.
The fastback swap hasn't been done yet, he has the parts and we worked out a deal to get them swapped over for this. I might even be helping him do it when I get there over the weekend so I should be able to get a good look under everything. Good to know about the wiring issues too. I'm sure once I see what the differences are I'll be able to work out a good solution for them. I really enjoy working with wiring so I'm ready to clean up a rats nest if I need to haha!
 

v6buicks

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Okay, I have another automotive confession. I've always wanted to toy with an 3.4 DOHC! Specifically, I've always wanted to swap one into a 2.8 S10. I'd turbo that sucker before going straight to the 3800. I think it'd be a high revving riot!

Either way, I look forward to seeing what you do to this sucker.
 

bs009

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I've seriously been considering that, especially since it's already running on MS3 lol. I haven't messed with an aftermarked ECU before so I'm pretty interested in seeing what it can do.
I haven't ever messed with the 3.4 dohc either so it's going to be new territory for me.

The only really cool thing I'm anticipating if I did turbo the 3.4 would be the sounds it makes with such a high rev limit. For some reason I thought they made more power than they actually do, but it looks like they only make about 215hp from the factory which really isn't much more than the L36's 205hp.

In theory at 15 psi the lq1 would make 430 crank compared to the L36's 410chp. I have no idea how strong the LQ1 is either so the L36 seems like a better choice, but if the LQ1 makes cooler sounds then it might be neat haha! And if it blows up then nbd :LOL:
 

bs009

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Fiero turned out to be shit and I think I asked way too little for what the car is right now. I'm thinking of hanging onto it a while longer until the next build is started/done now. The more I think about it the more I realize I don't need to sell it. I'll just try to get more garage space at my next house in the next ~5-ish years.

This thing got a TON of attention being towed around last weekend too, way more than it gets when I drive it around Detroit :ROFLMAO:. Right now I'm planning on taking it along for the TCG Tour this year if that happens.
 

v6buicks

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I'm feeling the same way right about now. Needing to pull the Camaro outside any time a daily needs something really sucks. Meanwhile, my Grand National usually just sits in storage. I can't wait to get a bigger space to work in and store stuff. I'm glad to hear that you aren't getting rid of the GP yet. A Fiero would be really cool too, but a completely different animal.
 

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