Engine ideas

[Hoop]

Hey Everyone,



I am of course, a new member here, I hail from Ohio, and I drive(on weekends) an '85 Fleetwood Brougham, as seen in my sig.

It has 99,000 miles on it, a few rust spots here 'n there, and of course, the notorious HT4100 with its 135hp and 200 ft lbs of fury!

I'm trying to decide what to do with it engine wise, even though the HT4100 is in good condition right now, I don't expect that to last forever.

My first weapon of choice would be a 500. Problems I'm running into with that, make me nervous to try it without some serious investments.

First off, the '85 was controlled with around a billion sensors, so I know i would need a new computer to start. Im worried about messing up the climate control, fuel economy(even though it wouldbt work anyway) and anything else electrical.

Second, anyone ever try to find a 500? They are getting pretty hard to spot, and ones you do seem to hit, they want alot of money for them.

my next weapon of choice, would be a 425. More abundant yes, but still, I run into my electrical gremlins.


Next on the list, replacing it with another 4100, or a 4500 or 4900.

I REALLY dont want to go with another 4100, and I dont even know if they make RWD applications of the 4.5 and 4.9.


Last option, and this is DEAD last, would be to have a GM 350 installed.
This is worst case scenerio, as I like to keep brands together, but if I absolutely HAVE to, then I will.


I have installed a 403 Rocket in a 87 Fleetwood around 2 years ago, but the guy forgot to number everything... so he got screwed there.

If I did the work myself though, it wouldn't be the first time


Sorry for the long first post, but I look forward to being here awhile, and hearing any ideas you guys might have.

[Stoneage_Caddy]

wow i didnt know the ht4100 was in rear drive apps , interesting

i dont think the 4.5 or 4.9 came in any rear drives but i could be wrong , but i wonder if the 4.1 block will accept the 4.9 internals,heads ,manifolds,crank and cam etc , wonder if itd be easier to put a 5.0 out of a 90 fleetwood in it ?then again it doesnt make that much more power , what what engine the 1989 caddy presidntail limo used ....

[davesdeville]

I haven't seriously looked for 500s yet, but I do know that around 750k were put into Cadillacs, although some were FWD versions on Eldorados. I don't know if the FWD setup would or wouldn't cause problems with a swap. If you can't find a 500, you're more likely to find a 472, as around 1.5 million were put into Cads (all RWD I believe).

[kcnewell]

The 4.5/4.9 engines did not come in a RWD configuration. The swap that you're contemplating is complicated but not impossible....I'd try to find a 472 if it was me.

[Hoop]

Yeah, the HT4100 was unfortunately used in a Rear Wheel drive applications, right after the great 4-6-8 368 Cu In. disaster.


I have been leaning towards the 500/472 for the longest time, but like I said, Im ultra weary about my electrical equipment working properly after the swap.

I considered swapping in an Olds 307(5.0), but then again, I really would not be getting myself too far

I want this car to remain stock looking, but I want it to be able to move itself, even beat up on the occaisonal Mustang or Camaro

When was the last time you saw a fast stock-looking 80's Cadillac? We are overshadowed by our Younger siblings with the LT1, which, I would not mind owning...

Maybe when I sell the Galant..

Anyway, thanks guys for your help so far, and if anyone has some insight on my electrical porblems, please shed me some light!

[Katshot]

Any of the Olds V8s are a good fit, and a fairly easy swap. A 307 wuld be a great engine but it IS low on power as you mentioned. The 350 would probably be my choice but you COULD go for the 403 as before.

[lux hauler]

I see you're in Ohio. I don't know what the laws are like in your county but if you have to deal with the emissions laws, you might have to stick with the same type motor.

If you're going with a different motor, you might as well go with your first choice......472/500.

I don't know what kind of mileage you get out of the motor you're running now but, it is possible to get 15mpg out of a well tuned 500.

472's/500's are out there, you just have to keep your eyes open to find them. This should be a good time of year to look also.....all the demo derby cars will either be for sale of getting scrapped.

Don't pass-up a 472 just because it's not a 500 either. It's every bit as good a motor.

[davesdeville]

But you can't say that you have the largest displacement V8 ever mass produced.

[cadillackman]

[quote=Hoop]Yeah, the HT4100 was unfortunately used in a Rear Wheel drive applications, right after the great 4-6-8 368 Cu In. disaster.


have you considered going for a late 70's olds 350 rocket?i used to have an 85 toronado and freinds told me that i could almost swap the two clean.,with minimal computer problems.a good cam swap would probly bump it past the 300 hp.mark.

[Brian Bray]

Jordan,

You may want to step back a minute and think where you'll be when you get finished and if that's desirable. You'll have a somewhat faster 100K Ohio car and that means rust (you said it ALREADY has SOME rust!) which will only rust more and will get LESS gas mileage at a time when gas will probably settle in at $1.50 - $1.75 gallon. Even if you install a NEW engine, everything else on the car is 18 years old and has 100K on it. You'll constantly be replacing or fixing something. Repairing rust never ends and is expensive. If you are driving around and hope to get anywhere near 15 mpg out of 472 cu. in., you are going to have to drive it MORE conservatively that you drive your car at present. Is that what you had in mind?

Keep in mind that the swap you are contemplating may make the car LESS valuable in the market when you are finished (I realize that it would be MORE valuable to you, but probably most others won't agree with you!).

To me, this means that the total cost you will be the cost of the project PLUS a good chance that the vehicle you'll end up with will be worth less (unless you find a buyer who thinks EXACTLY like you) than it is presently (and realistically that's probably not too much.. sorry!).

Therefore, I would suggest that if you still want to pursue this course of action, look for a low mileage car from the SW or S that someone has ALREADY performed the swap you have in mind. That is absolutely the least expensive way to achieve your goal and you'll have the bonus of a a rust-free, low mileage car.

Believe me, you have NOT invented the wheel in this matter; someone has already done the swap and with present gas prices may well want to sell the car; you just have to find that seller.

If so, that car may very well be priced LESS than the same car with a smaller engine.

So have patience, take your time, look hard, and take advantage of the reality of gas prices in the pursuit of what you want.

Brian Bray

Originally Posted by Hoop

Hey Everyone,



I am of course, a new member here, I hail from Ohio, and I drive(on weekends) an '85 Fleetwood Brougham, as seen in my sig.

It has 99,000 miles on it, a few rust spots here 'n there, and of course, the notorious HT4100 with its 135hp and 200 ft lbs of fury!

I'm trying to decide what to do with it engine wise, even though the HT4100 is in good condition right now, I don't expect that to last forever.

My first weapon of choice would be a 500. Problems I'm running into with that, make me nervous to try it without some serious investments.

First off, the '85 was controlled with around a billion sensors, so I know i would need a new computer to start. Im worried about messing up the climate control, fuel economy(even though it wouldbt work anyway) and anything else electrical.

Second, anyone ever try to find a 500? They are getting pretty hard to spot, and ones you do seem to hit, they want alot of money for them.

my next weapon of choice, would be a 425. More abundant yes, but still, I run into my electrical gremlins.


Next on the list, replacing it with another 4100, or a 4500 or 4900.

I REALLY dont want to go with another 4100, and I dont even know if they make RWD applications of the 4.5 and 4.9.


Last option, and this is DEAD last, would be to have a GM 350 installed.
This is worst case scenerio, as I like to keep brands together, but if I absolutely HAVE to, then I will.


I have installed a 403 Rocket in a 87 Fleetwood around 2 years ago, but the guy forgot to number everything... so he got screwed there.

If I did the work myself though, it wouldn't be the first time


Sorry for the long first post, but I look forward to being here awhile, and hearing any ideas you guys might have.