: The best engine to put in my Eldo Cadillac?



KINGUYOM
08-28-11, 06:58 PM
Hello all fans of Cadillac!

I have a big problem with my 1985 Cadillac Eldorado convertible, V8 engine 4100 ht is dying so I have to find a way to change it soon :(

Browsing the web, I saw a lot of guys who have so changed that infamous original engine with a V8 5.7 liter, 350 ... it with a carburetor.

I found several used engines on the web:


• Option 01:
A 5.7-liter v8 efi
who come from a 1976 Cadillac Seville

• Option 02:
A 5.7-liter V8 carburetor
who come from a Chevrolet Monte Carlo Landau Coupe

• Option 03:
A 5.7-liter V8 nine seen on the Summit website
This GM performance V8 350 195 HP Engine C.I.D base


Could you help me and tell me if these engines are mounted in my 85 Cadillac?
especially if they can adapt to my transmission
and my gearbox THM 325-4L?

thank you in advance for your valuable advice

friendly
William

83CADMAN
08-30-11, 12:24 PM
A GM 350…sound good to me. I have an 83 Eldo with the HT4100 and have often though about engine upgrade.
Cadillac offered a diesel, which by the way is an Olds engine based on the GM 350. I don’t know if they used a different transmission with the diesel option or not. If not then one would think that any 350 SB could match up to your stock bell housing. It’s all the computer stuff…

aeronca36606
08-30-11, 01:53 PM
Chevy 350 won't bolt up tp the transmission. The 1985 Eldorado used the old Buick Pontiac Oldsmobile bell housing. Chevrolet is different. With the space constraints with the THM325 transmission, I don't think a bell housing adapter would be an option. If you are going to use anything except the original HT4100 or 5.7L Diesel, Then your best bet would be either an Olds V8 or a Cadillac 368 or any engine in the 368 family. You could also use the Buick V6 as these where sometimes found in the Buick Riviera and Eldorado. (Usually in the 252ci version). Parts for the V6 conversion may be a bit hard to find though as this was a rare option. (I believe the V6 was available with a turbo also)

Take it from someone that has done a few engine swaps in vehicles not originally fitted with the engine being swapped in. Conversions are always a headache unless you have a complete parts car with the configuration you are shooting for. It is almost never the big things that hang you up. It is the small things that cause all of the trouble. Like cables mounts brackets fuel systems starters etc that cause most of the work and expense.

Unless you are looking for something the original engine can not provide (Performance?) then your best bet is to replace or rebuild the original power plant. The 4100 while not a power house by any stretch of the imagination, Is capable of propelling the car at reasonable speeds with reasonable performance while delivering excellent fuel economy. Fuel economy will only become more important as time goes on.

There is also the possibility that your non emission compliant conversion will be banned from the road by an un-caring Department Of Motor Vehicles. Some states are very hard on conversions and most will become so in the next 10 years.

Good luck with your project.

vincentm
08-30-11, 02:18 PM
Have you thought about getting the original engine rebuilt with possible updated gaskets, etc?

dennis93coupe
08-30-11, 04:29 PM
After following ehall's 4.9 conversion in his DeVille, I'd be tempted to try that. It would save a complete engine tear down.

KINGUYOM
08-30-11, 08:19 PM
Thank's a lot for your advices !

aeronca36606, i think you right about the fact to have a donor car is the more simple way,
a friend of mine have in his junkyard an CADILLAC ELDORADO 1981 With the 6.0 liter gasoline, may be i can buy it and transplate all the stuff to my eldo 85 ?

ps : i live in europe, so don't care about state law ;)
also, excuse me for for my bad english...

some picture of his car :

796837968479685

aeronca36606
08-30-11, 09:06 PM
That particular car has the other infamous engine of the 80's. The V8-6-4. The engine itself is a strong design along the lines of the 472cu and 500ci engine. The problems are with the Valve switching technology. This was an early attempt at variable displacement. Unfortunately the control systems where not as developed as they should have been. This said I had a Fleetwood 75 Limousine with this engine and it ran flawlessly. The Variable Displacement system worked 100% as advertised. This is my only actual experience with this engine and it was good. However there have been many that have had a lot of problems with it. You can disconnect a sensor on the trans that will effectively disable the Variable Displacement control. This will let the engine run in the V8 mode all of the time. I tried this once on mine and it ran just as any normal engine would. The fuel economy did go down quite a bit but not excessively. These are a tough engine though and are known to take abuse without causing mechanical failure.
Overall not a bad way to go in place of the HT4100.

As much bad publicity as Cadillac has had with respect to there 1980's designs, There was a lot of innovation during those years.
The HT4100 with all of its problems was in the for front of the move to electronic fuel control. It has some of the best on board diagnostics of the period. Even better than most of today's cars.
The V8-6-4 was the first attempt to integrate a Variable Displacement engine into a mass market.
The 5.7 Diesel was the first diesel experience most Americans had with Diesels. It sold in much bigger numbers than most people realize. It did have some problems with it's design (Most of which wouldn't have been there if accountants stayed out of the engineering of the engine) but was made reliable near the end of it's production run.
During the early 80's there was a lot of change at Cadillac and they did a fairly decent job while bringing a lot of new technology to there cars.

My favourite Cadillacs are the 67 to 70 Eldorado's. I have owned several of each and was sorry after each was sold. Your 85 is a sure to be classic and has some of the best lines of the era. It is also a great drivers car. I had a Brown 85 Eldorado and was very happy with it as a daily driver. (HT4100)

KINGUYOM
08-31-11, 05:01 AM
Thank's again aeronca36606 for your knowledge !

you say this engine is a V8-6-4 ?
i don't know how to recognize this engine
from a regular V8 6.liter :s

how to recognize it visually?

in the 1981 year, Cadillac make only this engine ? or they prodcut also regular V8 6.liter ?

thank's

friendly
William

aeronca36606
08-31-11, 03:08 PM
Quickest give away is the tall and oddly shaped valve covers with the electrical connectors for the Valve Disconnect.

I think the 6.0 was only in a V8 6 4 version. (Anyone correct me if i am wrong) I believe you can convert the engine to a conventional design. (Possible valve train or head swap)
You may also be able to use a 400ci or 472ci as i believe these used the same basic block but further research would be necessary.

KINGUYOM
09-01-11, 06:29 AM
thank's again aeronca36606

you a really cadillac expert !

i think in 1979 & 1980, they are not "regular" 6.liter only 5.7 liter....

some pictures to be sure i have understand :
7977479775

watajob
09-11-11, 03:25 AM
That is a V8 6 4. And, to be clear, 79 had a fuel injected Olds 350 lifted from the Sevilles of that time, 80 an FI 368 Caddy, 81 had the 8 6 4 and 82 - 85 had the 4100. The 368 is the small end of the 368/425/472/500 family.

KINGUYOM
09-11-11, 06:15 AM
That is a V8 6 4. And, to be clear, 79 had a fuel injected Olds 350 lifted from the Sevilles of that time, 80 an FI 368 Caddy, 81 had the 8 6 4 and 82 - 85 had the 4100. The 368 is the small end of the 368/425/472/500 family.

Thank's Watajob !
you say " caddy 79 had a fuel injected Olds 350 lifted from the Sevilles of that time"

that's mean it's not exactly the same engine ? the engine of a 76-79 Seville can be put in a 79 eldorado ?
can you explain the differences ?

thank's a lot
William

watajob
09-11-11, 12:25 PM
79 and 80 are totally different engines. As far as the swap, I don't know. 76 - 79 Sevilles were modified X bodies, (RWD). The new for 79 Eldo was part of the E body, (FWD), line. I'm sure there are people on here who could tell you. Or, try a search

KINGUYOM
09-12-11, 05:57 AM
79 and 80 are totally different engines. As far as the swap, I don't know. 76 - 79 Sevilles were modified X bodies, (RWD). The new for 79 Eldo was part of the E body, (FWD), line. I'm sure there are people on here who could tell you. Or, try a search

I search on the web, and i see a guy who swap the 4100 ht (fwd) by a 350 ci ( rwd)
and who said : the flywheel is differente
Flywheel (it's specific to FWD if you're using a RWD configured engine)

most of the time the 350ci from an Oldsmobile 98, but i don't know if the 76-79 sevilles have the same engine exactly ?

your opinion ?

watajob
09-12-11, 02:23 PM
I really couldn't give an opinion as I have no idea. I'm wondering if a post over in the Eldo/Seville forum might yield the answers you're looking for as there are some pretty knowledgeable folks over there. Sorry I couldn't be more help.

rambo45
01-31-12, 04:41 PM
well my suggestion to you is to use an oldsmobile 442 engine. i grew up helping my dad build race cars and the only car he drove was an eldo. In our quest to build a better running race car that would outrun, and last longer we started to see what engines could withstand the heat. Because my dad worked at an autorecking yard we had many cars to chose from, and we found an oldsmobile with a 442 engine. We tested the car out but the car was to heavy, so me and my dad had the idea to pull the oldsmobile's 442 engine, and placed it in his eldo. Because an eldo is alot lighter than most oldsmobiles, we where able to make a better running race car, and a better running car period with an engine that will last a long time.

KINGUYOM
03-01-12, 11:06 AM
thank's rambo45 !

in fact, i need a daily driver eldo, and I think I will consume too much gas with this engine.... in my country gasoline costing two dollars per liter ( that's a shame) :(

83CADMAN
03-01-12, 09:12 PM
In post #6 you were considering a 6 liter engine?? Now there is a thirsty beast. Stick with the orig 4.1, it burns reg gas and will get reasonable gas miliage. Or maybe a Buick 6 cyl out of a Riviara? You could turbo it.

KINGUYOM
03-02-12, 07:30 PM
thank you Cadman83

Oops, you're right, sorry my fault,
I'm confused and I thought that the 442 Was a racing engine,
bigger than 6 liter .... misread the message writting by rambo45

sprocket
04-24-12, 01:38 PM
I've got a 4.9 in place of the 4.5 on my '88 Eldo. I have the original intake from the 4.5 so it is still throttle body injection. The fuel injectors are a little undersized for the 4.5 so I compensated by doing a simple procedure that makes the fuel pressure regulator adjustable. I then booted the fuel pressure about as high as I could which was a little over 12 lbs. That's about the only changes I made. The idle is not quite smooth and I have tried every thing under the sun to correct it. It's not a very big deal though. The engine runs great other than that and I get pretty good fuel economy. The avg economy shows 23 mpg right now but I need to confirm that. Changing the fuel pressure could have affected the accuracy of computer calculation for mpg.

I'm not real familiar with the 4.1, but if the throttle body injection is the same as the 4.5, then you might just need to get injectors from a 4.5 and then increase the fuel pressure like I did. (to change to a 4.9)

ehall
04-25-12, 12:53 AM
When I swapped a 4.9 under my 4.1, I used chevy 305 injectors. The 4.9 is 299 CI so 305 is pretty close.

sprocket
04-25-12, 01:32 PM
When I swapped a 4.9 under my 4.1, I used chevy 305 injectors. The 4.9 is 299 CI so 305 is pretty close.

I did that too at one point. I bought rebuilt ones. I found that the diagnostics showed that the engine ran rich at first until the computer got the feedback from the O2 sensors and then it would go into closed loop and be OK. There still seemed to be a tendency towards the rich side though.

After going back to the 4.5 injectors and increasing the fuel pressure, the lean issue right after start-up went away, or at least wasn't as dramatic, and once in closed loop, the cross counts are usually very high. My engine seems to like this combination better.

creeker
05-02-12, 11:39 PM
MY 1980 coupe deville had the 6.0 liter, 368 engine which is stock for that year,maybe cost a little more for gas, but it's a very reliable and durable engine.

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[QUOTE=creeker;2954015]MY 1980 coupe deville had the 6.0 liter, 368 engine which is stock for that year,maybe cost a little more for gas, but it's a very reliable and durable engine.[/QUOTE

I should have mentioned, it is not the 8-6-4-, If I was you I would disconnect the 8-6-4. feature and invest a bit of money into the engine your friend has, they are a great
engine, get it running for as little money as possible and see if it's worth further investment.