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Engines swap 56 Caddy to 390 engine

Started by #1CaddyFan, January 27, 2020, 06:29:50 PM

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#1CaddyFan

Hi All I need info on swapping a 390 from a 59 sedan Seville into a 56 Coupe along with the tranny does anyone have experience that could guide me in the changeover ? Thanks in advance.

Cadman-iac

Hey Dan,
My '56 coupe had a 390 in it before I bought it, and as far as I can tell it fit just fine.  The person I got it from had already begun to attempt to transplant a SBC into it when I found it though.
I did get the  390 engine and the transmission with it.  I thought it was the original engine for a long time until I began looking into rebuilding it. That's when I discovered the swap.
I can tell you that the oil filter is located on the right rear of the engine instead of being mounted on the top.
The engine mounts both look the same as well as the transmission mount.
Physically there doesn't appear to be any difference in size at all. I don't know about the crank pulley clearance because I don't have the original one to compare.
That's about all I can offer you for information about this swap,  but from what I've seen on my own,  it should work with minimal problems.
Best of luck,
Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

#1CaddyFan

Hey Rick,
Thank a lot for the info. That will really simplify my decision making on the engine for my 56. The seller has a good 390 engine/tranny from a 59 Seville he is going to drop in the car for transport to me. According to info I have found here and in the net the two engines use the same block and the 390 is a bored out version of the 365 so your experience verifies that. It's good to hear It from someone for sure vs reading It somewhere. It did not have the 365 in it when he purchased it and the previous owner told me that it was missing the engine when he owned it for several years awaiting a restoration effort. It has changed hands a couple time after it left Tennessee and now it is coming back to become a weekend driver if my efforts do well. Thanks for the engine advice
again.
Dan

35-709

"I can tell you that the oil filter is located on the right rear of the engine instead of being mounted on the top."

1960 was the first year for the spin-on filter at the right rear underside.  1959 still had the canister filter up top --- unless the Seville engine had it earlier.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

#1CaddyFan

Thanks,
That means the 59 and 56 engines look identical as well. The oil filter being remote mounted canisters. I watched a year down on a 60 and the filter was at the passenger rear.
Dan

#1CaddyFan

Thanks guys
Darn spell check keeps adding words I don't type.
Werth !

Cadman-iac

Quote from: 35-709 on January 27, 2020, 10:11:17 PM
"I can tell you that the oil filter is located on the right rear of the engine instead of being mounted on the top."

1960 was the first year for the spin-on filter at the right rear underside.  1959 still had the canister filter up top --- unless the Seville engine had it earlier.
That was my mistake,  I had checked the year on the one I have and it is a '62. I didn't know they changed the filter that late.  I thought it was with the size change in '59. Sorry for the mistake.
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

Roger Zimmermann

The transmission tail is much shorter on the 1957 to 63 models. you may have some difficulties with the drive shaft, it will be too short.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

#1CaddyFan

Thanks Cadman-lax:
If all goes well I should have the original trans from the 365 as well as the trans and 390 motor combo I might have to change drive shafts or tailshaft I will know more when everything arrives. Am I correct in that both motors share the same tranny bell housing pattern ? That is what I have read from several sources.
Dan

Roger Zimmermann

Yes, Dan, the bell housing pattern is the same. You will be faced with another problem: the cooling. The 1956 transmission has an external cooler while the 390 has a heat exchanger built into the radiator.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

#1CaddyFan

Hi Roger
The ole saying about draining the swamp apparently applies to Cadillacs as well.....I am up to my a%$ in alligators.....lol ....now it's cooling system issues ....so I have two trannys one engine no radiator yet. How did the 4speed hydromatic cool it's self if not from the radiator cooling tank ?

Lexi

#11
I have a spare engine radiator if you are interested. I believe it came out of a 1955 Cadillac. Same as the '56, except they put the drain cock on the other side. Other than that they are the same rad. I would consider this a core for rebuilding even though said to have come from an operating car. Drop me a line if interested.

Edit: Check out this link for trany cooler line info. You may want to consider an aftermarket cooler that mounts behinds your grille, depending on what you do. That way you still by-pass the rad and keep it looking reasonably period correct but with improved cooling. Here is the link: http://forums.cadillaclasalleclub.org/index.php?topic=110099.0

Clay/Lexi

Roger Zimmermann

On the following copy from the parts book, the cooler has the group number 20.0110. On '56 cars, the cooler is under the flywheel housing; the picture here is for the 1957 set-up.
Be aware: in the insert "Oil pressure regulator valve parts", the plug group 20.1808 is not correctly illustrated. In the shop manual, the orientation is correct.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

#1CaddyFan

Thanks for the info on the cooling system and trany. When I get the Caddy and assorted parts I will have a better idea of what to do. Until then (April 2020) I am trying to absorb as much knowledge as I can.
Dan

SixDucks

The exhaust manifolds used may need to be from the '56 engine. I'm not certain about this, but I thought I remembered reading a thread on the Modified Cadillac forum about installing a 390 into a '56.

Terry
Current:
1941 coupe
1962 Fleetwood
1988 Brougham
Previous:
1956 Series 62 Sedan
1963 Fleetwood
1975 Fleetwood Brougham D'Elegance
1989 Brougham

#1CaddyFan

Thanks SD
I think I read that on here as well about the manifolds.