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Technical 1951 Pontiac Straight 8 into a 33 Pontiac.

Discussion in 'Traditional Hot Rods' started by casper50, Sep 19, 2022.

  1. casper50
    Joined: Aug 4, 2013
    Posts: 230

    casper50
    Member
    from alaska

    I have access to a 1951 Pontiac straight 8. I'd like to swap out the straight 8 in my 33 Pontiac as it's locked up. Is there a way to do away or adapt the enclosed driveshaft? I'd rather either keep the original rear end or swap something in that I can still run the original wire wheels. If I swap I'll have to put in a hydraulic brake system for the rear. I'd rather keep it as simple as possible.
     
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  2. flynbrian48
    Joined: Mar 10, 2008
    Posts: 7,641

    flynbrian48
    Member

    Seems like a poor choice for an engine swap. They're horrible, even in a '51 Pontiac...
    Edit: To try to be helpful as opposed to just snarky, if you have one, and that's the reason, using a bad engine just because you have one is a not a particularly good idea. They are saddled with (most likely) a huge, heavy, inefficient 4 speed Hydromatic. You'll end up spending a fortune to convert your closed drive, and if you're gonna swap a different rear end, might as well drop in a modern power plant. A Chevy 250 or 292 and 700R4 would me my choice, and a rear end from an early 90's Cadillac Fleetwood or Buick Roadster wagon. They're 5 on 5 (which I think your car has) and even if they don't, drilling axle flanges is no big deal. Don't ruin your car with the straight 8...
     
    Last edited: Sep 19, 2022
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  3. stuart in mn
    Joined: Nov 22, 2007
    Posts: 2,231

    stuart in mn
    Member

    He's talking about swapping the engine, nothing was said about the transmission. I'm not that familiar with Pontiacs that old, but would think if you're just switching one straight 8 for another it should be straightforward. They weren't known as a hot rod engine but I sure wouldn't call them horrible.
     
  4. casper50
    Joined: Aug 4, 2013
    Posts: 230

    casper50
    Member
    from alaska

    I don't want a modern engine in it. Rather keep it a straight 8 as it came.
     

  5. PhilA
    Joined: Sep 6, 2018
    Posts: 1,734

    PhilA
    ALLIANCE MEMBER

    The '51 straight eight traces roots back to the thirties- that's why it's so terrible (it's not terrible. It's just poorer than a lot of engines in terms of making big power and fuel economy, and the dynamics of it are way worse than a V8.) so it's not an inviable swap. The mk1 Hydra-Matic is actually more efficient at cruise than the TH350 because its fluid coupling doesn't slip as much as a torque converter. They're just picky about fluid, heat, phase of the moon and not as smooth or trouble-free as the later transmissions.


    Horses for courses.
     
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  6. Should be a viable swap.... the straight eight in its basic form was used for about 20 years. But.... there no doubt were some subtle changes. Can you get the two engines side-by-side to compare? My guess is you'll see some motor mount changes, accessory changes, etc., but it shouldn't be insurmountable. You might try the Pontiac-Oakland club (they probably have an online forum), as I would imagine this swap has been done more than once. Good luck!
     
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  7. TCTND
    Joined: Dec 27, 2019
    Posts: 355

    TCTND
    Member

    Probably easier and cheaper to just rebuild the original.
     
  8. casper50
    Joined: Aug 4, 2013
    Posts: 230

    casper50
    Member
    from alaska

    cracked block
     
  9. I thought this is a HOT ROD forum! Any and all things possible.:D:D

    Go for it, Casper50. I never had a Pontiac as old as yours. Did have a 1948. In 1957!!
    I have no idea how to make it fit but bet you will do so.
    Good luck.

    Ben
     
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  10. HEATHEN
    Joined: Nov 22, 2005
    Posts: 7,904

    HEATHEN
    Member
    from SIDNEY, NY

    Well, the length and weight certainly won't be a problem. If you're lucky, they're like early Chevrolet sixes that had one block pattern for the bell housing from 1937-62.
     
  11. PackardV8
    Joined: Jun 7, 2007
    Posts: 960

    PackardV8
    Member

    Does anyone have an old J.C. Whitney catalog? IIRC, they sold a steel brace kit for the Pontiac straight eight. It was so long and with the motor mount system Pontiac used, the block would literally sag.

    jack vines
     
  12. fyrffytr1
    Joined: Dec 20, 2016
    Posts: 464

    fyrffytr1
    Member

    I have a 50 and a 39 with straight 8s and other than the carburetor/intake I can't see any difference. Does your car have a manual or automatic tranny? Not that I see any great difficulty in swapping just the motor.
     
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  13. casper50
    Joined: Aug 4, 2013
    Posts: 230

    casper50
    Member
    from alaska

    33 has a manual 3 speed. It's also frozen. Wife want to drive it when it's finished so I need the auto. Sounds as if it will become a real headache but I'll work through it.
     
  14. That wifey thing!! I installed AC in mine so wife could ride along. You guessed it! ONE TIME. I seldom turn it , AC, on.:rolleyes::rolleyes:

    Ben
     
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  15. I used a Toyota rave 4 rear end in my 34 chev truck .
    57 inches wide wms to wms . 4.11 posi .12 inch hydralic brakes , same 6 bolt pattern as chev, whole gear pot pulls out same as a 9 inch . 33 spline axles , parts readily available ,cheap from rock auto .
     
  16. 6sally6
    Joined: Feb 16, 2014
    Posts: 2,057

    6sally6
    Member

    Sounds like a "Block-brace"(anti-sag)...is a smart choice. You could prolly make one!
    Standard hot rodding tricks like split exhaust.....maybe add another carb onto that looong intake(or bigger one)...
    Delta Cam or others could re-grind the camshaft for ya...maybe mill the head a dab to bump up that miserable CR.. free flow muffler(S)................you-be-in-business!!!
    6sally6
     
  17. 40two
    Joined: Feb 19, 2012
    Posts: 2,104

    40two
    Member

    It isn't terrible at all, i rebuilt my original straight eight and it's going strong, no oil consumption, running up hills like a young girl, starts on the first pedalpush and makes nearly 16 mls a gallon. You can do 300 miles in one piece without any stress. With my small tent camper on the hook that weight including some camping equipment about 600 lbs i also had no lack of power.
    and it's easy to fix, too.
     
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  18. casper50
    Joined: Aug 4, 2013
    Posts: 230

    casper50
    Member
    from alaska

    40two I agree. Not everyone needs or wants lots of horsepower in a car. Reliable, smooth running and easy maintenance is a huge plus for some of us.
     
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  19. PhilA
    Joined: Sep 6, 2018
    Posts: 1,734

    PhilA
    ALLIANCE MEMBER

    Yup, done 4500 miles on this one. Needs a valve job because it sat for 6 months outside and still has a sticky inlet valve.

    But, it's smooth, has an exhaust note you don't hear these days (inclusive of the very particular flathead type noise you get, the hissing chatter), starts stops and doesn't overheat. Has a little trouble getting up to 55 im a hurry by today's standards but is really happy if not pushed hard down the highway.
     
  20. casper50
    Joined: Aug 4, 2013
    Posts: 230

    casper50
    Member
    from alaska

    55 in a stock 33 will be plenty fast I'm sure.
     
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  21. PhilA
    Joined: Sep 6, 2018
    Posts: 1,734

    PhilA
    ALLIANCE MEMBER

    Yup.
     
  22. carbking
    Joined: Dec 20, 2008
    Posts: 3,426

    carbking
    Member

    Congrats on keeping it on a similar platform, and all Pontiac. :)

    Performance parts (aluminum head, twin carburetor intake) were produced once, but you have to have a crystal ball to find them today, and own an oil well to pay for them if you do find them.

    Even stock, the 1951 engine produces 50 percent more power than the 1933 (116 hp versus 77 hp).

    And you can add 5 more by changing the Carter 720s (original) to the Carter 2122s (1954 version).

    Should make a nice running car!

    Jon.
     
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  23. fyrffytr1
    Joined: Dec 20, 2016
    Posts: 464

    fyrffytr1
    Member

    You mean like this intake? I picked it up at a local swap meet about 5 years ago. It is going on my 50. edmunds 3.jpg
     
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  24. fyrffytr1
    Joined: Dec 20, 2016
    Posts: 464

    fyrffytr1
    Member

    It would be a lot easier to teach her how to drive the manual and once she learned she would love it. My wife does.
     
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  25. carbking
    Joined: Dec 20, 2008
    Posts: 3,426

    carbking
    Member

    fyrffytr1 - better lock your hood! ;)

    I haven't seen many of these, but memory (sometimes faulty) remembered one drilled for the 4-bolt carbs.

    And ditto on the wife driving a manual. I taught mine to drive a 4-speed in a 12.2 second Corvette about 1966.

    Jon.
     
  26. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,364

    302GMC
    Member
    from Idaho

    Used to have this stuff hidden away for when I found a '54 Star Chief coupe. Didn't get to use it ... More Pontiac 009.JPG More Pontiac 001.JPG More Pontiac 007.JPG More Pontiac 012.JPG
     
  27. carbking
    Joined: Dec 20, 2008
    Posts: 3,426

    carbking
    Member

    302GMC - that is the one I remembered.

    Jon
     
  28. fyrffytr1
    Joined: Dec 20, 2016
    Posts: 464

    fyrffytr1
    Member

    This one will fit the motor but I will either have to get adapters for the four bolt or put three bolt carburetors on it. I think a set of Strombergs would do the trick.
     
  29. fyrffytr1
    Joined: Dec 20, 2016
    Posts: 464

    fyrffytr1
    Member

    302GMC
    I noticed the aluminum head in your first picture. I check the Pontiac classifieds every day here but a few years back I missed one day and that was the day someone posted two of them for $800.00! Of course they sold immediately. I even messaged the buyer to see if he would sell one but he had plans for both.
     
  30. aussie57wag
    Joined: Jul 13, 2011
    Posts: 452

    aussie57wag
    Member
    from australia

    I think that would way cool. Yes it will take a bit more effort. But how cool will it sound and look. With multiple carbs and duel exhaust. If properly built and maintained it should be dependable. Who says you have to run an auto. But if an auto necessary you could adapt a turbo 700 to it.
     

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