🔧 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!

bs009

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Took the car on a roadtrip this week since I had some vacation time to burn. Figured I'd self-isolate in my car for a few days.
Did a few bucket list locations with it, but wish the weather had been a little nicer for them.

The trip started great, I forgot how fast this thing is. It really blows me away when it builds boost and starts hauling in second. I went down south hoping to find some warm weather but didn't fair so well. Still managed to have a lot of fun with it though!

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It's crazy to see how low the air pressure is even just at 6,000 feet. 80kpa there.

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Also interesting to see that the autometer boost gauge references the relative air pressure and not absolute air pressure.

Found myself near the tail of the dragon eventually and figured why not? lol!

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On the way home though I got tired of trying to find E85 and went to 93 octane again. I do this quite a bit on longer road trips so I didn't think it'd be an issue. My boost controller hasn't been working very well lately. It's always hitting 20 psi in second and third gears and it looks like that was too much for the 93 octane gas.

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No idea how much knock there was or what the AFR's were. It happened so fast. Did a pull in second gear, about a second later it felt like it lost power so I let out thinking it was the trans trying to shift, got back in it and felt a lot of lost power after that.

Manged to limp it home about 7 miles on 5 cylinders but it looks like the car is going to take a break.
 
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Mr_Roboto

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With the amount of people who swear that opening up a 3800 bottom end is the kiss of death I'd be curious to know how long one would survive like that.

Hell if I know. People used to worship the stock GN head gaskets too. . Joliet U-Pull It has em for $18 a piston/rod. Then again for $265 without a core you can get a whole engine.
 
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v6buicks

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True that. I just get really curious about where people get these notions. There are a lot of people who say you can't rebuild a Buick engine EVER without extensive block work which is bogus. If it was good enough from the factory and it's not damaged it car certainly live again. You just need to use some sense when putting everything together. Short blocks are a lot more than nuts and bolts.
 

bs009

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Luckily I have a spare L36 lying in my garage already. It needs gaskets because the previous owner used RTV for basically everything. I'd like to do things as cheap as possible but I also want to do more mods if I'm already putting another engine together. (maybe porting and polishing, maybe trying different intakes, maybe fixing the way the exhaust is routed here and tossing the A/C to make room for a bigger turbo, idk).

I've been planning on doing a full build down the road here (Aluminum heads, big cam, etc.) but I wanted to wait at least another year before I do that.

It'll probably cost about $100 in gaskets alone to get the other motor in there so this won't be a big deal. I already have ARP head studs lying around so it'll be cool to finally use those and it'll save like $20 lol.

It is still an L36 but I'm not convinced that the L36 bottom end is an issue yet. I have an L67 and L36 engine sitting in the garage and I'm planning on using the L36 for the higher compression. There is so much more power to be had with the L36 because of that. I know the rods and pistons are not as strong but I've never heard of anyone breaking them from too much power yet.
I'll just need to get a proper boost controller so I keep it safer when I run 93 or just get a bigger tank for E85.
 

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Phatride sent his l36 rods through the block at about the 500whp range and plenty of people have crack the ringlands. With a turbo you don't NEED high compression not that the difference between the two is even that big. You're talking about at the very peak of your power level a gain of about 2-4% with the higher compression. I would use the l67 which has proven to take abuse and not throw rods, they only spin bearings but same goes for all of the other GM V6's.
 
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bs009

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Sounds like I need to find some more details about that then.
I don't know if I'll hit 500 wheel yet any time soon with this motor.

I'll definitely plan on building another motor when I go all out here though and I'm sure I'll end up starting with an l67 for that. The oiling thread James has has a ton of good info that I'd love to do to the next motor too.

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If I use the l67 short block can I use my l36 flex plate though lol
 

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The l67 doesn't need to be built, just toss a turbo cam in it and go. Don't waste your money, you can go well over 500whp with one of those and it's factory assembled so it won't eat itself to death. Even the oiling mods are useless, just put the motor in and go live your life, it'll be fine.
 

v6buicks

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If you put everything back to where it went you're good, it's people that tried to put forged bottom ends in them, almost all of those spun bearings and died.
Do you think it's because of the parts or the builders? I figured it was people just not taking the care of measurement and making sure all the clearances were set right. I've never watched anybody successfully rebuild a 3800 with aftermarket upgrade parts. However, if there's one thing I've learned from Buick engine builders, it's that a Buick engines most common failures are due to an unknowledgeable builders. They aren't Chevys by any stretch and cannot be built as such. Buying one set of bearings and dealing with a rod or two being a little on the edge of the tolerance isn't going to turn out well. Having multiple bearing sets to find the perfect clearance is really important... and tedious work.

By no means am I saying it's black magic or impossible to build up a 3800 short block. I just know that corners must not be cut on Buick rebuilds, and 3800s are just a decedent of the same family. Luckily, the L67 is incredibly stout as it is. GM learned a lot from the Buick V6 Stage 2 racing program and applied some of it's principles into the 3800. If it were me, I'd want to learn first hand just how strong an L67 before I start building one up for insurance. If anything else, I'd do it because it's much cheaper and readily available.
 

Mr_Roboto

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Do you think it's because of the parts or the builders? I figured it was people just not taking the care of measurement and making sure all the clearances were set right. I've never watched anybody successfully rebuild a 3800 with aftermarket upgrade parts. However, if there's one thing I've learned from Buick engine builders, it's that a Buick engines most common failures are due to an unknowledgeable builders. They aren't Chevys by any stretch and cannot be built as such. Buying one set of bearings and dealing with a rod or two being a little on the edge of the tolerance isn't going to turn out well. Having multiple bearing sets to find the perfect clearance is really important... and tedious work.

By no means am I saying it's black magic or impossible to build up a 3800 short block. I just know that corners must not be cut on Buick rebuilds, and 3800s are just a decedent of the same family. Luckily, the L67 is incredibly stout as it is. GM learned a lot from the Buick V6 Stage 2 racing program and applied some of it's principles into the 3800. If it were me, I'd want to learn first hand just how strong an L67 before I start building one up for insurance. If anything else, I'd do it because it's much cheaper and readily available.

I don't question the SBC methods of building as much as I question the level of care for such a build in general. If you tell a shop you're building a high performance 3800 I could see them kind of rolling their eyes and being like "whatever" then building it like a basic 3800 that's going in someone's 200HP bonneville despite someone making more than double or triple its original HP and cramming 20+ PSI down its gullet.

The l67 doesn't need to be built, just toss a turbo cam in it and go. Don't waste your money, you can go well over 500whp with one of those and it's factory assembled so it won't eat itself to death. Even the oiling mods are useless, just put the motor in and go live your life, it'll be fine.

Based on looking the difference seems to be the pistons that'd get kicked out in a build anyways. I'd rather build the dead L36 up and either sell the L67 off to someone who needs one for $$ to bankroll a build or toss it in and go.
 

bs009

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Whichever one I use this year will pretty much just get tossed in there with just new gaskets. For the moment I really just want to get it running again without putting much money into it.
I kinda want to see how much power I can get out of the stock cam and e85 before getting a different cam. If the limit is 500 wheel for the L36 then I should be okay with the stock cam afaik.

In about a year or two I'll definitely be looking to follow all of this advice here and start with the L67 short block though and go with a big cam, decent heads and a bigger turbo to see how far it can go. That might end up going into a different platform though-we'll see what happens.

I'll have to look into the compression ratios more then. Conventional knowledge would suggest I'd be a lot better off with the point and a half of compression to start with but I know you all have seen a lot more high hp builds than I have. Maybe I'll start another thread about that then.
 
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bs009

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I'll have to look into the compression ratios more then. Conventional knowledge would suggest I'd be a lot better off with the point and a half of compression to start with but I know you all have seen a lot more high hp builds than I have. Maybe I'll start another thread about that then.

Found out that I've been comparing the L36 vs L67 power output without correcting for power lost from driving the blower.

For fun this is what the difference would be between the two for each pound of boost pressure:
L36L67
#'s of boostHP#'s of boostHP
0
205
0​
194​
1​
219​
1​
207​
2​
232​
2​
221​
3​
246​
3​
234​
4​
260​
4​
247​
5​
273​
5​
260​
6​
287​
6​
274​
7​
301​
7​
287​
8​
314​
8
300
9​
328​
9​
313​
10​
342​
10​
326​
11​
355​
11​
340​
12​
369​
12​
353​
13​
383​
13​
366​
14​
396​
14​
379​
15​
410​
15​
393​

Still thinking of just using the L36 so I don't have to deal with getting my flexplate balanced unless I can just drill it out for the RWD pattern. I'll have to see how different the FWD vs RWD flexplates are when I pull the engine out.
 

Mr_Roboto

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Whichever one I use this year will pretty much just get tossed in there with just new gaskets. For the moment I really just want to get it running again without putting much money into it.
I kinda want to see how much power I can get out of the stock cam and e85 before getting a different cam. If the limit is 500 wheel for the L36 then I should be okay with the stock cam afaik.

In about a year or two I'll definitely be looking to follow all of this advice here and start with the L67 short block though and go with a big cam, decent heads and a bigger turbo to see how far it can go. That might end up going into a different platform though-we'll see what happens.

I'll have to look into the compression ratios more then. Conventional knowledge would suggest I'd be a lot better off with the point and a half of compression to start with but I know you all have seen a lot more high hp builds than I have. Maybe I'll start another thread about that then.

The question of compression has always been a thing that is somewhat controversial in the Buick Community.


According to the book how to build horsepower going from 10:1 to 8:1 is worth 3.7% output na. May affect spool a bit but without camming you are going to leave a lot of the benefit on the table anyways.

I. Surprised they are different balances. Isn't this an internal balanced engine?
 

bs009

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Yeah that's another hug debate I hear about all the time and I've heard anecdotal evidence both ways about how you can and can't swap them with some people swearing it shook their motor to run the other flexplate, and some say they've ran L36 flywheels without having them balanced for years with no issues.

From what I understand it is supposed to be internally balanced. There is some difference in the flexplates in the way the weights are stacked:
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Looking at the two in my garage though there are a few other differences though and those weights could just be trying to account for some of the extra drilled holes in the L67 flexplate:
L67:
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L36:
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It's probably not a big deal though.
 

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