Register now to get rid of these ads!

Technical V8 swap in a 1948 Pontiac

Discussion in 'The Hokey Ass Message Board' started by silverstreak48, May 20, 2020.

  1. silverstreak48
    Joined: Oct 1, 2018
    Posts: 4

    silverstreak48

    Hi! I’ve been thinking about doing a v8 swap in my 1948 Pontiac. It currently still has the straight 8. Does anyone have any advice about how to go about this? Also, where the motor mounts would have to be placed? Any advice would be greatly appreciated! I’ve been told that there is a conversation kit for 48 Chevy that would likely work, but I’m guessing I’d have to put a Chevy motor in it. We’re trying to stick with a Pontiac motor if possible. Thanks!
     
    jakespeed63 likes this.
  2. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,647

    gimpyshotrods
    ALLIANCE MEMBER

    GM back then was not like GM later on, with "badge engineering". Unlike later cars, GM vehicles were actually quite different across the brands.

    Parts for a Chevrolet might be able to be modified to work, but how much modification is hard to say.

    In all likelihood, the mounts would need to be fabricated.

    As for where they would be located, you'd have to suspend the replacement engine in the engine compartment, make sure that the fan is the correct distance from the radiator, and work from there.

    Non like-to-like engine swaps, or swapping to a different engine, even of the same brand, if it was not an alternative optional engine, almost always requires welding.
     
  3. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,583

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Very doable with a Pontiac V8. A step by step here would be lengthy. There are books on engine swaps...look for one on Motor Books website. Also, an excellent post on a recent thread written by @ekimneirbo with photos and text. Plan on removing the 'front clip' (fenders, grille, radiator core support as a unit) for clear access to frame. Removing clip is not that difficult and pays big dividends.

    Ray
     
    Hombre, silverstreak48 and i.rant like this.
  4. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,647

    gimpyshotrods
    ALLIANCE MEMBER

    Yup, plenty of room up there for about any engine, too.
     

  5. GeeRam
    Joined: Jun 9, 2007
    Posts: 370

    GeeRam
    Member

    Here in the UK, this lovely thing has a '60s era 425 Nailhead fitted in it......seems to make it move along the road quite well :D
     

    Attached Files:

    gimpyshotrods likes this.
  6. VANDENPLAS
    Joined: Dec 14, 2009
    Posts: 2,669

    VANDENPLAS
    Member

    Not sure where you located.

    min Canada pontiacs where built on Chevy frames.

    adapting engine mounts is no big deal
    Most guys use the hurst front mount on these as it’s easy to install
     
  7. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,583

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    @VANDENPLAS OP's car has "straight eight" .........not likely a Canadian build car.
     
    gimpyshotrods likes this.
  8. jimmy six
    Joined: Mar 21, 2006
    Posts: 7,115

    jimmy six
    Member

    Sheeat.... I’d put in 2 SBCs you got plenty of room. Seriously to make it easy, get an empty engine and trans and give yourself room around the trans and steering moving it a bit in every direction. good luck
     
    silverstreak48 likes this.
  9. wvenfield
    Joined: Nov 23, 2006
    Posts: 5,119

    wvenfield
    Member

    I'm glad to see you plan on keeping it Pontiac (just my personal preference with a Pontiac).

    As noted above the easiest way is likely to get or make a front engine mount.
     
  10. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,215

    mgtstumpy
    Member

    Totally different frames if US manufactured; Chevy is top hat with bolt in front suspension so mounting kit won't work in a Pontiac frame which has open/boxed 'C' channel frame. A Pontiac in a Pontiac would be a nice touch. Whilst at at, don't skimp on upgrading your brakes, steering and/or suspension. Depending on what engine/trans combo you use, think about Hurst front mounts and also fabricating a rear transmission support member. I swapped a SBC into my 46 Olds frame (Similar to Pontiac) and had to fine tune eng/trans location to allow driveshaft to exit centre X-member with sufficient clearance for rear suspension movement.
    [​IMG]
    48 Chevrolet

    upload_2020-5-21_9-32-6.png
    Pontiac (Example with V8)
     
  11. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,647

    gimpyshotrods
    ALLIANCE MEMBER

    Excellent info, Sir!
     
  12. fyrffytr1
    Joined: Dec 20, 2016
    Posts: 310

    fyrffytr1
    Member

    I am watching this thread. If the straight 8 in my 50 doesn't last I will probably swap to a Pontiac V-8.
     
    silverstreak48 likes this.
  13. silverstreak48
    Joined: Oct 1, 2018
    Posts: 4

    silverstreak48

    Thank you. I’ll have to look into the website. It’s just called motor book?
     
  14. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,583

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    PM sent.
     
  15. I was in a car club in the '50's. There were 2 brothers with Pontiacs of that vintage, both had Olds V-8's with hydros. Not rocket science.
     
  16. belair
    Joined: Jul 10, 2006
    Posts: 8,530

    belair
    Member

    A really cool swap would be the OHV Pontiac 250 six.
     
    dan c, Torkwrench and wvenfield like this.
  17. tubman
    Joined: May 16, 2007
    Posts: 5,210

    tubman
    ALLIANCE MEMBER

    This was common in Minnesota in the late '50's. early '60's.

    Hydra-Matics rule!
     
  18. tubman
    Joined: May 16, 2007
    Posts: 5,210

    tubman
    ALLIANCE MEMBER

    Uh, NO. These are relatively heavy cars. Why would you want to cripple one with anemic engine like this and add parts scarcity into the equation?
     
    hidez57, Hnstray and gimpyshotrods like this.
  19. wvenfield
    Joined: Nov 23, 2006
    Posts: 5,119

    wvenfield
    Member

    Scarce? Yeah, you do see them though. Even in stock form a late one will have more than double the HP of the stock engine.
     
    VANDENPLAS likes this.
  20. tubman
    Joined: May 16, 2007
    Posts: 5,210

    tubman
    ALLIANCE MEMBER

    And the torque would be.....?
     
    Hnstray likes this.
  21. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,583

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Torque moves cars......horsepower doesn’t......hp is a byproduct of torque. You can make a chainsaw engine produce impressive horsepower...IF...you turn 20,000 rpm.....but it would be useless.
     
    gimpyshotrods likes this.
  22. wvenfield
    Joined: Nov 23, 2006
    Posts: 5,119

    wvenfield
    Member

    260. The stock 1948 8 had 190.

    Add headers and triple carbs (Pontiac did do this to a special performance engine) and claimed 315 HP. (No, I don't know the torque but one can roughly guess).

    So while maybe OT a 1948 Pontiac is generally thought of as a low rider, not a stoplight car. With that in mind the OHC 6 would be different and kinda cool IMO. The last OHC 6 I saw for sale went quick.
     
    Last edited: May 23, 2020
  23. belair
    Joined: Jul 10, 2006
    Posts: 8,530

    belair
    Member

    Uh YES. The original worked for decades, and the OHC would run circles around the flathead six or 8. I put a Chevy 250 in my 48 Fleetline with a th350 and a 57 Chevy rear end. It ran great, ate up the hiway, chirped the tires in second gear when I wanted. So Uh, speak of what you know, not what you think.
     
    wvenfield and firstinsteele like this.
  24. 3600 to 4100 lbs depending on model and engine. A 6 cyl Firechicken weighed 3080.
     
    Last edited: May 23, 2020
    Hnstray likes this.
  25. tubman
    Joined: May 16, 2007
    Posts: 5,210

    tubman
    ALLIANCE MEMBER

    Since the car was originally a straight eight, how's about a compromise and stay with one? I envision a hopped up 320 ci Buick Roadmaster engine. I used to race with some guys that ran those. They bored 'em out a full 1/4" (!) and used pistons from an International Harvester tractor to give 356 cubes and added hi-lift rocker arms and 5 or 6 Strombergs (depending on how many they could find). If you could find an Edmunds head and intake, I could also see a 356 ci Packard.

    I like different, interesting cars.:D My definition of interesting doesn't include a 250 ci 6 cylinder in a two ton car.
     
  26. wvenfield
    Joined: Nov 23, 2006
    Posts: 5,119

    wvenfield
    Member

    390 lbs torque @ 4000 rpm.

     
    dan c, mgtstumpy and belair like this.
  27. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,583

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Though my post(s) did not endorse the Pontiac OHC 6 for this application, I am a fan of inline engines. I am member #057 of Inliners International, obviously dating back to their early days.

    I am in fact currently building a ‘37 Chevy coupe with a 250 Chevy six that has been warmed up and dyno’d 258 lbs ft and 226 hp. It was modified specifically with an eye towards torque. The ‘37 Chevy coupe is a relative lightweight and for my purposes, I think will perform very satisfactorily. Nonetheless, as has been stated by others, the weight of the Pontiac in question is quite a lot heavier.

    In addition, the Pontiac OHC engines, while certainly not extinct, don’t seem to be all that common. And most certainly the factory high performance versions were rare when new, much less fifty years later.

    Further, the OP has indicated limited experience with engine swaps in general, and asked about the suitability of a Pontiac V8. Taking that into consideration suggests to me that the swap should be simple, straightforward and use readily available components.

    Ray
     
    Last edited: May 23, 2020
    jakespeed63 and tb33anda3rd like this.
  28. yep. good advice
     
    VANDENPLAS likes this.
  29. fordflambe
    Joined: Apr 9, 2007
    Posts: 516

    fordflambe
    Member

    When born, my 48 Convertible had a straight 8. It was long gone and i wanted to stay Pontiac so this is my build with a 389. Plenty of room............


    AUT_8419.JPG AUT_1740.JPG AUT_9209.JPG IMG_1568.JPG Mar_14_2019_6x2s.JPG
     
    Sporty45, VANDENPLAS and slim tempo like this.
  30. tubman
    Joined: May 16, 2007
    Posts: 5,210

    tubman
    ALLIANCE MEMBER

    I LIKE that (except for the rear wheels; I expect they're only temporary):rolleyes:.
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2020 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.