transfere heads to old block

Discussion in 'Early Cadillac Engines' started by 55caddyguy, Jun 6, 2016.

  1. 55caddyguy

    55caddyguy Member

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    Hello Guys, my 390 , 1960 block is shot. It froze over the winter and spider cracked. I had this rebuilt and it only has 2 hrs at most run time. I have the original 331 block that came with the 1955 caddy. I have no money to invest in redoing another block. I want to use the 390 heads and performance cam in the 331 motor before I install back in the car. How do I go about this and do I use the push rods from the 390 and lifters? Leave the old lifters in place? I want to get this car running by the end of the month for my daughters grad. I still need to reassemble the car once I get it from the body shop this Wed. Short time line with lots of late nights. Thanks in advance. G
     
  2. Schurkey

    Schurkey Member

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    I thought the 390 was a tall-deck version of the 331. If that's the case, the 390 pushrods are probably too long.

    I suspect the cam will slide right in. Doesn't mean the grind will be optimum for the smaller displacement, though.

    Far as I know, the heads should work just fine--but check combustion chamber size to determine compression ratio. Also verify valve-to-piston clearance in case the 390 uses larger valves that might interfere with the valve notches in the older pistons.
     
  3. 55caddyguy

    55caddyguy Member

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    I did the change out this weekend. Taking the cam out of the rebuilt motor was a bitch, had to hammer it out from the back of the block. Taking the cam out of the 331 was no sweat. So I installed the cam, lifters and push rods from the 390 block and heads from it. All fit fine. I need to get the timing set and fire it up. I found that the push rods are the same size for both motors, length and thickness. Only difference is if you use new style lifters or the old style. The old style are counter sunk more than the new ones, so need a slightly shorter pushrod. It was no problem doing the swap placing the 390 heads to the 331 motor. :metal:
    Will see what kind of performance I get once the car is put back together.
     
  4. The Mad Cadder

    The Mad Cadder Well-Known Member

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    You hammered the cam out and have installed another in a motor that you
    intend to use ??

    That dosent sound good hope i misunderstood something
     
  5. 55caddyguy

    55caddyguy Member

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    Yes that is correct I hammered out the cam to free it from the bearings. It slid in nicely into the 331 motor. No nicks or damage.
     
  6. El Diablo

    El Diablo Active Member

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    Any updates on this?
     
  7. CrashTestDummy

    CrashTestDummy Member

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    I read that as he had to hammer the cam out of the 390 (frozen block) but it slid into the 331 easily, so probably no damage.
     
  8. 55caddyguy

    55caddyguy Member

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    I need to find a drivers side header that will clear the steering gear box. I put the project on hold until I finish building my 2000 sq ft shop.
     
  9. pila78

    pila78 Well-Known Member

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    When I was a young guy, I bought a '55 Coupe DeVille that 2 years old. Nice car, except that the brakes were the worst I ever encountered !! These days, they could likely be up-dated to disc type, at least on the front...
     

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