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Studillac: 331 vs 390

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  • Studillac: 331 vs 390

    Can a 390cu work as easily as a 331cu in a 1953 commander? Someone told me there was a block difference with the 360/390, but I thought the block change was not until early/mid 1960s? Any info / advice about the 50s caddy engine installs is appreciated.


  • #2
    '49-54 331" had the extended bell housing and require their own adapter. The '55 -'62 365" and 390" have a modern flat back block. For the '63 390" and '64-69 429", Cadillac revised it with shorter connecting rods and was 1" lower, 4" narrower, and 1.25" shorter. The accessories (water pump, power steering pump, distributor) mount on a die-cast aluminum housing at the front of the engine for improved accessibility. An alternator replaced the generator. The crankshaft was cored out lighter and stronger. The '63-67 Cad engine is 52# lighter than the '49-62, approx 595#; so shorter, lighter. narrower, it may fit better in a Stude.

    FWIW, I have a '63 390" Cad core - $350; completely blueprinted with all new wear parts, $3995.

    jack vines


    • #3
      Jack obviously is very well versed in the cad motors. He provided all the differences between the different versions. As a big picture thought I'd just say that there is a lot of interchangeability between all the cad v8s from 49 through 63 and generally where one fits, any of them will.

      Lovely motors too. High quality, powerful and about the same weight of our well loved Studebaker v8's.

      His offer of the 63 Cad motor sounds pretty good too.
      Diesel loving, autocrossing, Coupe express loving, Grandpa Architect.


      • #4
        Back in the day I had a 64 Caddy with 429 engine Powerful yet good on gas. cheers jimmijim
        sigpicAnything worth doing deserves your best shot. Do it right the first time. When you're done you will know it. { I'm just the guy who thinks he knows everything, my buddy is the guy who knows everything.} cheers jimmijim*****SDC***** member


        • #5
          Back in the day, I had a 67 Eldorado with 429. Excellent motor, but it needed the 24 gallon gas tank, and probably coulda used a 55 gallon tank. I recall 8-9 MPG, but that was mostly town and country, and very little interstate. If putting a Caddy motor in a Stude, I'd go with the 429.


          • #6
            My FIL had a 68 fleetwood with the 472, IRRC. I remember getting 19 mph on a trip to Chicago back in the day. We didn't drive real fast but did not poke either.
            Diesel loving, autocrossing, Coupe express loving, Grandpa Architect.