: Guidance & Advice Needed: 83 Fleetwood brougham 4.1 engine swap

07-31-11, 09:18 PM
I know this has been mentioned a few times on this forum. I'm looking for specific guidance and general advice on replacing a 4.1 (HT4100) engine with something with more horsepower. I'm leaning towards an olds 455... from what i hear this would be a good swap and should match up to the original tranny (although i'm open to changing transmissions to match an engine i will be happy with).

I'd like to hear from someone who has done this before or any general advice on the subject.

I'm looking to ditch all the glam and computerized nonsense that came with the car. I've already taken the engine out and its basically a shell awaiting a new engine. This is a project i have been putting off for about 5 years but looking to finally get it done. I'd like to get my old car back on the road again as a weekend driver.

Thanks in advance for any help on the subject. :)

07-31-11, 10:17 PM
What are you looking for in a weekend driver? 455 would be a good engine for the car but you would have to put, at least, a 700R4 tranny behind it.

07-31-11, 10:43 PM
^Right. The THM 200 (the stock transmission) is not durable enough to hand the power of the 455. The THM 700 is a Chevrolet transmission (with overdrive), so you will need a Chevy to BOP bell housing adapter. Another option would be the TH 400, which does not have overdrive, but would bolt directly to the 455.

cadillac kevin
07-31-11, 11:30 PM
the stock turbo 200 trans will get destroyed the first or second time you drive it so upgrading to a beefier trans is a necessity. I'd go for a turbo 400. only 3 gears and no overdrive, but its what came with the 455's originally

@csbuckn, just out of curiosity how much torque can a stock 700r4 handle?

07-31-11, 11:35 PM
I don't know how much a stock one can handle but I think you can build them to handle pretty much anything. My guess is gonna be a little under 300lbs of torque.

08-01-11, 11:11 PM
What are you looking for in a weekend driver? 455 would be a good engine for the car but you would have to put, at least, a 700R4 tranny behind it.

What am i looking for? Well by weekend driver i mean i'll just be driving the cady at most once or twice a week, so maybe an entire day once a week. I'll be driving the car in California so obviously i need it to be able to handle the hills and mountains. There will be some highway driving as well.

I don't recall the exact make of the original stock transmission that came with the car... one of those THM types. I'll do some research on the 700R4 and try to learn more about it. Thanks for the help.

Would the 700R4 be the best choice? Is there anything you can tell me about this tranny?

cadillac kevin
08-01-11, 11:50 PM
your car originally came with a turbo 200 (THM200-c) if I remember correctly. it was an incredibly weak transmission that could not even stand up to the 200hp corvettes back then.
the 700r4 is a 4 speed auto with overdrive and lockup torque converter. it was mostly used behind 350 chevys. they're pretty durable and stronger in stock form than the turbo 200, but weaker than the turbo 400.

08-02-11, 12:03 AM
The 200R4 trans in stock form is garbage, but they were also put behind the 86-87 turbo Buicks with different internals. Just saying don't write the 200R4 off, but plan to spend some $$$ on a good rebuild with higher quality parts. Lots of turbo buick guys run that trans with 500hp and aren't gentle on them.

The 700R4 and 4l60e isn't all that great of a tranny either IMO, I blew one up in my 99 Z28 Camaro with 100k miles on it. I didn't beat on it that hard IMO, just normal Camaro use, maybe about 15-20 passes down the quarter mile, only time I did a big smoky burnout was when it was new tire time.

Good info on the 200R4

08-06-11, 11:17 PM
Hey Aron thanks for that link.

That shop is just a few miles from me so I'm planning to give them a call and pick their brains a little.

08-07-11, 01:59 AM
^ That's too funny, I just typed in performance build 200R4 or something like that on google and gave you that link.