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| Swapping out a 2.5 for a 3800 supercharged (Page 1/1) |
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mike01
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JUL 05, 04:46 PM
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I have an 84 SE with an original 2.5L engine with a stock manual transmission. I was given a 1999 Buick Regal with a 3800 supercharged engine with an automatic transmission. I'm a competent mechanic and wondering what issues I should expect during the engine swap. I'm wanting to stay with the manual transmission setup. Will the original transmission mount to the 3800 engine (even if temporary)? Are the engine cradles interchangeable?
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cartercarbaficionado
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JUL 05, 09:39 PM
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| quote | Originally posted by mike01:
I have an 84 SE with an original 2.5L engine with a stock manual transmission. I was given a 1999 Buick Regal with a 3800 supercharged engine with an automatic transmission. I'm a competent mechanic and wondering what issues I should expect during the engine swap. I'm wanting to stay with the manual transmission setup. Will the original transmission mount to the 3800 engine (even if temporary)? Are the engine cradles interchangeable? |
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yes the transmission will bolt up to the engine. cradles do not interchange
theres alot of swap information but the 84s are a bit weird but i find much easier to deal with (as they use a 70s style harness or full size harness running power through the solenoid) so i would use the ecu harness from the other car to relocate the main connection away from the exhaust
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Frenchrafe
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JUL 09, 11:30 AM
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Hi, yes you can do it. Keep the gearbox in place on it's mounts and mate up the engine.
You should be able to reposition the lower engine mount towards the rear to line up with the Fiero cradle mount fixation. (Some fab work maybe to modify slightly the fixation on the 3800 motor?)
You could keep all the stock rubber Fiero mounts, but they won't hold up long to the power/torque output. Especially the foward gearbox mount.
Once you have the whole thing positioned properly, then you need to beef up the motor mounts and the gearbox mounts. Either go Rodney Dickman (if he still has any?), or make your own.
TH400 poly mounts are perfect for the gearbox; you'll have to fabricate the base plates, but it's noting more then some thick steel plate cut to shape and rewelded. Copy the orignal rear gearbox mount (lower part) with two big studs welded on to take the TH400 mount.
The front gearbox mount is just two plates welded together at about 125° opening (mock it up and tack it because I'm not sure of this angle any more?), this time with holes for the TH400 mounts and studs for the cradle fixations.
The lower engine mount is just a simple "cotton reel" poly bush mount, like the dogbones (torque struts).
For the dogbone, you just have to be creative with bits of plate or corner section bolted to the upper part of the engine somewhere to get something to line up for the dogbone (which is nothing more than two cotton reel mounts and a length of tube welded between the two.)
I personnaly added some simple corner sections to the cradle to make lower dogbone attachements and fixations on the block (lots of unused threaded holes to choose from) so as not to use an upper dogbone (my charge pipe goes right through where the stock dogbone would be).
Oh, and of course you'll need a machined down 4th gen 3800 Camaro flywheel and a clutch. (Personnaly I would go with a SPEC clutch and flywheel - torque and more torque! But this may be challenging if you are on a budget?)
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"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero
https://youtu.be/hUzOAeyWLfM[This message has been edited by Frenchrafe (edited 07-09-2025).]
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