Cadillac 331 365 390 info shared

Early (pre-1968) Cadillac engine discussion.

Cadillac 331 365 390 info shared

Postby nitrohonkey » Sun Feb 01, 2009 12:13 pm

I am posting this because It has been difficult for me to to find info on these engines. I began toying around with these engines over the last couple of years...I am building a 1962 cad 390 for my 36 ford. What I am sharing is my experience thus far, but I do not claim to be an expert! Feel free to correct me if I am misled; feel free to add to this post to help others!WANTED speed parts for 331-390 Cadillac engines!

The 331 was the first overhead valve Cadillac engine. Early 1949 engines had "center-bolt" valve covers rather than the perimeter style bolts common to later engines.
I believe that somewhere between late 54 and 1956, the 331 became extinct and the 365 was born. Although they are similar engines, there is a great deal of difference between the 331 and 365. The 331 has a portion of the bell housing cast to the back of the block like an Old's rocket 301...I believe they share the same flywheel (Olds 301/ 324 and Caddy 331) The CAD 331 only parts are:engine block, distributor, exhaust manifolds, and rocker shafts are different in appearance, seem to work on a later engine. I have heard the heads will interchange with later engines, but exhaust ports are smaller and spaced differently than later engines. 331 are lower compression than 365/390.
Interchangeable parts between 331 and 365/(390 through 1962) are: valve covers, valley cover, water pump, pulleys, valve covers intake manifold, timing cover and heads(but I believe push rods have to be altered and valve relief issues come into play)

365 and 390, up through 1962, are very similar. Only major difference is stroke/ displacement and the oil filter. 365 has remote oil filter like a 331 and 390 has a spin-on oil filter on the lower passenger side of engine block. Although NOT interchangeable with other GMs, 365 and 390 engines @ the back of the engine block where transmission mates are designed much like late model GM engines(ie small Chevy).
If you want to adapt a ford or GM manual/auto transmission to the rear of these engines check out They have just about any type of adapting combination one could conceive...just make sure you do not have a shy wallet!
1963 is a weird engine....
distributor is moved up front, much like a ford v8. Water pump was redesigned along with timing cover and valve covers are different than earlier model engines... I have 1963 heads on my 1962 390 and 1952 331 script valve covers on the 63 heads.
I believe the 429 was born from the 1963 390 engine???

Anyone know if 429 heads are interchangeable with 390????
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Re: Cadillac 331 365 390 info shared

Postby kadillackid » Mon Feb 02, 2009 2:05 am

;)  A bit more on the subjet....the 59 390 still retained the remote filter system like the earlier years, 1960 was the introduction of the full flow filter mounted on the lower passenger side. The 1957 pump I believe was a odd one where the inlet was on the opposite side as previous years and later years. If looking for a dual quad intake and wish to run later model carbs, try to source a 57 model with the casting number 1469263 as this has the later AFB type carb bolt spacing, the Edelbrock  AFB and AVS type bolt right on with no need for adapters. The earlier intakes have the WCFB bolt pattern.
1957 Intake Eldo.jpg
1959 Cadillac Coupe on Air Ride / 390ci
1975 Cadillac Coupe lowered  / 500ci
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Re: Cadillac 331 365 390 info shared

Postby Gary » Fri Feb 13, 2009 1:11 pm

Transmission adapters are also available here:

Expensive, but made from steel plate.
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