1980 Eldorado Coupe 368-swap for a 500

nitinnelapudi2 · #1 (**permalink**) 08-28-08, 12:25 PM

Has anyone done a swap for a 368 on an Eldorado coupe from the 79-85 era? I have a 1980 cadillac eldorado coupe with a 368 (without 8-6-4). I want some power so I heard it is fairly easy to swap out the 368 for the 500 or other bbc engines. Anyway I talked to my mechanic and he said he doesn't know if the it will fit in the eldorado coupe. even thought they are ths ame blocks he has a feeling it won't work...Any ideas? Has anyone done this before? Any ways to mod up the 368? cams, chips, etc?

***Lord Cadillac*** · #2 (**permalink**) 08-28-08, 01:10 PM

I do believe this has been done before. Do a good search within this section of the forum. Otherwise, let's allow other to chime in...

Welcome aboard! And thank you for signing up!

Edahall · #3 (**permalink**) 08-28-08, 02:09 PM

I remember someone swapping in an Olds 403 to replace their HT4100.

carnut · #4 (**permalink**) 08-28-08, 03:59 PM

In 1980, at least in Calif. the only engine was an Olds based 350 fuel injected gas engine or a 350 Olds diesel. So any big block Olds engine would potentially work. 403's from Trans Ams and Olds 98's would work. The oil pan, exh. manifolds gear linkage brackets A/C brackets and front eng. mounts from a 350 diesel of that era from a Eldo, Seville or Toronado would be necc. The electric fuel pump would be unplugged at the fuel tank and the mechanical pump would then be used. I would also use the oil cooler adaptor from the diesel as well. least expensive way would be to buy a complete diesel front wheel drive car.

455Eldorado · #5 (**permalink**) 08-28-08, 05:04 PM

Hi!

I've swaped the original diesel with the Olds 455 some time ago. The only thing I had to find was the accelerator cable. All the brackets, accesories, oil pan are from the diesel engine. Later on I replaced the intake manifold, water pump, pulley, radiator,....with aluminum to reduce the weight. The front was too heavy with the big block in the car.

Regards!
P.

nitinnelapudi2 · #6 (**permalink**) 08-29-08, 07:06 PM

Yes this is true, in California the engines were oldsmobile made, either the olds 350 or olds 350 diesel. The eldorado was also outfitted with the smallest of the cadillac big blocks in 1980 the 368 without the 8-6-4 function and also in 1981 which was also the 368, but with the 8-6-4 function. My question is, since the 1980 eldorado is smaller than other cadillacs of that year is it possible for the 500 or other big block caddy engines to fit inside the chassis of the car? does the other caddy big blocks other than the 368 have larger deck heights or other dimensions that are physically different than the 368? I am trying to fit a 1979-85 cadillac eldorado body style with a big block caddy engine (other than the 368) that is currently housing a 368 engine...is there any problems that might come to mind for you experts out there that might cause for concern. My mechanic is willing to do it, but I would rather know of any difficulties before i fork over tons of money...don't get me wrong i know it costs, but i would like to get a general Idea of the problems so I can estimate costs.

carnut · #7 (**permalink**) 08-29-08, 07:24 PM

Too much fabrication on a Cad engine. Oil pans, oil pump pick up tubes, exh. manifolds, motor mounts and then you still have the weak transmission. I doubt you will find any info on the 500 install.

nitinnelapudi2 · #8 (**permalink**) 08-29-08, 07:37 PM

so your saying none of the parts that are on the 368 would fit the 500 to fit the caddy? what im saying is, couldn't i take all the oil pans and pick ups from the 368 and fit it onto the 500 to make it work? also would a smaller big block work? per say the 472? because the 500 is too strong for the tranny, would a smaller less torquey/hp motor work? I just got rid of my 4.1 for this 368 and now im still still stuck with a less than powerful engine for this car...is there anything that can be done to the 368 for better performance?

drmenard · #9 (**permalink**) 08-30-08, 01:35 PM

The 500 will fit in with very little mods...almost none....The 472 will fit in with no mods.. but the problem is the transmission ...All the torque could distroy it.As long as you are not going to race it , it might be ok... But if all you wanted was a bit more power, you could put in a 425 out of a 77-79... It will bolt in with no mods .. you will have to use the 368 pan and some other bolt on parts off the 368...

nitinnelapudi2 · #10 (**permalink**) 08-31-08, 04:26 PM

Just to make sure Im hearing this right... the 500/472/425 would fit in the car (79-85 body style) with no obstructions (like deck heights and all are same?) basically what im saying is the car's engine bay is big enough to hold the larger cubic inch engines with out any problems? Remember this is the smaller of the eldorado's, not the 76' big body.... what type of tranny do i need to make the 472/500 work? will it be able to replace the current tranny without mods?

455Eldorado · #11 (**permalink**) 09-01-08, 03:23 PM

I've been using the same original THM325 transmission with the Olds 455 engine (350hp) for 7 years now. The only thing modified is an additional oil cooler and a shift kit from Transgo. I don't race the car and even if I wanted to the front wheels loose traction very quickly.
As far as i know the THM435 will not fit because it is too big. Additional weight of the big block is a problem without the heavier THM425 in anyway.
The Olds 455 seats higher than the stock 350 and deck could be a problem with some intake manifolds. Don't know about Cadillac 500 engine though...

P.

nitinnelapudi2 · #12 (**permalink**) 09-03-08, 02:22 PM

Thats a very interesting setup you got...350hp under tha hood? bet that eldo gets up and goes! Ive been wanting to do that for yrs with my ht4100. In fact last yr I bought a 1983 olds tornonado to get all the fwd drive parts to switch my ht4100 to a olds setup. wish I kept it. I now have a 1980 caddy eldorado with a big block 368, and I want to put something in there that will give it some pep, you know? what yr is your caddy? so would you say that if i stuck a 425 ci caddy block (i think 180 hp) it would be fine with the tm325? the guy at aamco said if i put it in the car it would be fine as long as I don't hit the gas at a dead stop, but thats what I want to do, i want to burn some rubber, ya feel me? any suggestions?

455Eldorado · #13 (**permalink**) 09-04-08, 02:54 AM

It's true...with 350hp in there under the hood it just flies! Who knows what the top speed would be...the suspention is not up to it. Maybe with touring suspention package available as an option back than and performance steering box, wider low profile tires....The fastes I went was about 100mph.

I was told the same thing about transmission. Top speed doesn't matter but
hitting the gas from dead stop could kill it. I was however also told that with FWD and stock wheels/tires it will be hard to do much damage since the wheels loose traction real fast (FWD). It is kinda hard to take off on wet road...Still, o-60mph is way bellow 10s on dry road and no tire burnout.

I have a 1981 Biarritz, 3 speed (wider chain&sprocket drive than the 324-4L)
originaly diesel equiped. The swap was real easy!

I guess for rubber burning you need a rebult transmission with performance clutches, shift kit,....can be done but costs around 1200usd or more.

nitinnelapudi2 · #14 (**permalink**) 09-04-08, 02:59 AM

1981 with an olds engine? interesting ... so it was a olds deisel engine and you just swapped it out for a 455? how much did it cost u? for your car couldn't you get stiffer springs for the susp? man i jealous!!!

455Eldorado · #15 (**permalink**) 09-04-08, 04:27 AM

The swap was cheap and easy. I had the Olds 455 from a wrecked 1976 Toronado already and the only thing I had to buy was the accelerator cable.
Most (if not all) of the accesories, brackets,...is from the diesel engine.

The 455 is taller than 350 so the deck height could be a problem. The '76 Toronado, also FWD, has a recessed intake manifold and it fits under the hood. The weight became a problem though and the front was heavy in corners so I reduced the weight by replacing anything I could with aluminum...
intake manifold, water pump, radiator, crank pulley (diesel pulley is very heavy),...and is handles just right now.

There are no harder aftermarket torsion bars (front) for these cars. The easy and cheap way is to find a car with touring suspention and swap the rear spring, front bars and sway bars. Can't tell for sure but I suspect diesels have stiffer front bars as well due to heavier 350diesel engine. Shocks...those are easy to find but don't make much of a difference.

Regards!
P.