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Technical engine swap 331 to 390

Discussion in 'The Hokey Ass Message Board' started by raybhotrod, Sep 11, 2021.

  1. HEY GUYS DOES ANYONE KNOW IF IT IS A EASY SWAP A 331 FOR A 390 IN A 1950 CADY 62 CP
    Thanks Ray
     
  2. oldiron 440
    Joined: Dec 12, 2018
    Posts: 2,410

    oldiron 440
    Member

    Why do people type in all caps, don't they realize it represents yelling?
     
    Mr48chev likes this.
  3. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,180

    d2_willys
    Member
    from Kansas

    Depends on what year 390. 1963 390s are different than early years.
     
    wvenfield likes this.
  4. BUT YELLING AND ALL CAPS WORK FOR HARD-OF-HEARING, HALF-BLIND OLD FARTS LIKE ME, YOU WHIPPER SNAPPER!!!!
    But, sorry OP, I don't know anything about Cadillacs.
     

  5. Moriarity
    Joined: Apr 11, 2001
    Posts: 21,894

    Moriarity
    SUPER MODERATOR
    Staff Member

    331 are an extended bell block while 390’s are not. So at the least the transmissions are different. Also the exhaust ports on a 390 are much larger so the 331 exhaust manifolds will not fit.
     
  6. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,041

    Mr48chev
    ALLIANCE MEMBER

    Well the good news is it looks like both have rear sump oil pans. 331 being the red one 390 being the blue one.
    The early trans isn't going to bolt on the 390 and you would need to either buy a spendy adapter if one exists or use a Turbo 400 or maybe BOP automatic of choice behind the 390.
    Most likely having to fab or modify mounts.
     

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  7. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,041

    Mr48chev
    ALLIANCE MEMBER

    After that, in any engine swap where the same exact series of engine is going back in the vehicle such as replacing a 283 Chevy with a 327 or 350 or a 292 Ford with a 312 you are going to run into some issues.
    Things to consider:
    Oil pan sump design and location. This is a deal killer on a lot of same brand engine in same brand cars as a lot of later engines had the sump on the other end of the pan. If the distributor is on the same end of the engine you are usually good, if it is on the opposite end you are in for a hassle most of the time. For those who are asking "what the hell did he mean by that?" the oil pump and distributor drive off the same gear on the cam on almost all engines and if you have a front distributor it means that the deep part of the pan is going to be in the front. That won't clear the crossmember and often the steering on a lot of rigs that came from the factory with an engine with a rear mount distributor.

    Motor mounts and how they attach to the engine and chassis.

    Bell housing flange design on the engine. = what trans fits or is there and adapter available?

    Outside dimensions of the engine compared to the old one. A lot of engines that are quite similar got quite a bit taller and V8's got wider when the stroke was increased moving heads and exhaust closer to things like upper control arms.

    Cylinder head orientation; meaning which head sits forward or behind the other head as they are never straight across even. The that should be an easy swap becomes not so easy when you figure that on the engine you took out the Number one hole was on the drivers side and that head was an inch or so forward of the passenger side and the one you are putting in has number 1 on the passenger side and the left head wants an indent in the firewall before the engine will fit.
     
  8. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,180

    d2_willys
    Member
    from Kansas

    A 1955 Cadillac hydramatic would probably bolt to the 390, as 1955 up engines are Not extended block. Hard to find. Super hydramatics will bolt up to 390, but you will need at least driveshaft mods done.
     
    Deuces and pkhammer like this.
  9. pkhammer
    Joined: Jan 28, 2012
    Posts: 685

    pkhammer
    Member

    d2_willys is correct. I have two 331 Caddys both from 1955. Neither have the extended bell. I believe all '49-'54 engines have the extended bell but '55 and up do not.
     
    Deuces likes this.
  10. Good boy i am 83 and growing and dont care if I write in caps ,does it really matter
     
    Barrelnose pickup likes this.
  11. Jessie J.
    Joined: Oct 28, 2004
    Posts: 399

    Jessie J.
    Member

    Glad to see you still active and participating.
    Short answer to your question. Easiest and cheapest way is to use the transmission that came with the engine. or a same year or newer replacement.
    Adapting post 55 engines to any of the earlier transmissions to requires expensive adapters.
    Putting a high torque 390 in front of a 1950 vintage trans will be detrimental to its longevity, unless it is totally rebuilt to withstand the doubled h.p. and t.q.

    OR... is it that your '50 already has a 390 and you wish to return it to 331 power?
     
  12. sorry guys i did not say i have an adaptor for a built 200R trans to hook it up to the 390 Thanks
     
  13. Barrelnose pickup
    Joined: Aug 20, 2008
    Posts: 1,348

    Barrelnose pickup
    ALLIANCE MEMBER

    Like has been said, drive shaft, trans mount, exhaust.
    If you have a gearbox already for the 390 then maybe not much more than eng mounting.
    I have a 49 331 and a 59 390, not a lot of difference.
     
  14. Thanks guys if its just that its a cake walk
    Ray from the land of taxes and morons

    Only car guys and bikers are smart
     
  15. samurai mike
    Joined: Feb 24, 2009
    Posts: 506

    samurai mike
    Member

    i put a 61 390 in a 54, exhaust hit the power steering box. i have a 63 with a 58 engine and i'm getting ready to put a 63 390 in a 51. older motor mounts will bolt on to 63's.
     
  16. Dangerousdan
    Joined: Apr 12, 2018
    Posts: 270

    Dangerousdan
    Member
    from Arizona

    Thanks for the photo's. Really enjoyed.
     
  17. dan c
    Joined: Jan 30, 2012
    Posts: 2,250

    dan c
    ALLIANCE MEMBER

    we have a fella in st. louis that uses all caps due to poor eyesight.
     
  18. i just blow up the print
     
  19. Jokester
    Joined: Jan 29, 2005
    Posts: 536

    Jokester
    Member

    CTRL + scroll will make most things larger...

    Alas, it doesn't work on the one thing you really want larger.

    .bjb
     
    Jessie J. likes this.

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