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caddy 500 vs m-21 = BAD?

Discussion in 'The Hokey Ass Message Board' started by Rad Rob, Sep 4, 2009.

  1. I'm going to pick up a 1976 caddy 500 this weekend. The idea was to use it in my '39 chevy pickup with a model-a chassis for a unique ride. I wanted to use my m-21 in that truck but I hear bad things about caddys having too much grunt and I don't want to blow up the trans.

    My other option for the engine is to yank out the 400sbc from my '53 pontiac sedan delivery and use the caddy in that behind my rebuilt th350 (that conveniently has a BOP/Chevy dual pattern housing) I can then use the 400 in the '39 with the m-21 and live happily ever after. I even have a set of '55 chevy fenderwell headers I can use on the '39 if I go this route.

    Not getting the caddy engine is also an option, I do have another 400sbc sitting on a stand awaiting re-assembly. ;)

    This is as far as I've come with the '39 pickup, exept now it sits on the model-a frame instead of a pallet.
    [​IMG]

    And the pontiac, well it just got new lower quarters and the front clip finally went back on after the engine swap.

    [​IMG]

    [​IMG]
     
  2. Any large Caddy worth it's salt will rip the guts out of either tranny you mentioned.

    Both are good trannys, but the Caddy is much bigger than either one was designed for.

    You will find it very worthwhile to find a TH400 and use it.
    They are almost bulletproof, and may be the only reasonable choice for a big Cad. at a reasonable cost.

    Any other option I can think of is either way too weak, or way too costly.
    TH400's are really tough and relatively cheap compared to all the other options.
     
  3. Ricks57
    Joined: Feb 11, 2006
    Posts: 76

    Ricks57
    Member
    from San Diego

    Hi,
    I think it depends on how you plan to use the truck. If you're a drag race/performance type guy you'll probably eventually blow it up. If you don't power shift and dump the clutch at 4000 rpms it'll probably last if it's in good shape to begin with. The muncie was pretty much the only performance transmission for many, many years.
    Rick
     
  4. I'd consider selling/trading the muncie for a th400 if that's the case. I'm pretty stuck on the idea of a caddy engine, I've been looking for one for about 4-5 years now. :cool:
     

  5. skwurl
    Joined: Aug 25, 2008
    Posts: 1,620

    skwurl
    Member

    Doe the person you are buyining the engine from have the caddy trans?. I may be able to get my hands one one.
     
  6. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    Personally, I'd run the M21. Neither of the projects seem like they're headed in a pro street direction with huge sticky tires and drag race suspension.

    The key thing to remember is you can only load your transmission as hard as the back tires will allow. M21s came in plenty of big block muscle. Good luck with the project
     
  7. Neither one of these projects are going to the drag strip. I have a muscle car for that purpose that gets me into the 10 second bracket. :D These are just for cruising and general horsing around in town... that's the idea at least. The m-21 is an all aluminum unit with a straight line shifter and I put an aluminum bellhousing with a hydraulic clutch on it from an '80's chevy pickup so it will be easier to adapt when the time comes. I've noticed flywheels are expensive for the caddy engines so I may trade/sell the muncie for a th400.

    The engine is not coming with a trans. unfortunatley, it would have been FWD anyways.
     
  8. i just put a Muncie M-20 behind my 425 horse caddy so far so good. I had a T-10 in it for 23 years before it gave out.
     
  9. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,378

    dave lewis
    Member
    from Nampa ID

    3 things to consider...
    Pontiac flywheel.
    Edelbrock intake (with stock eldo intake, the carb sits LOWER than the intake ports )
    Pilot bushing needs to be custom made ( cad crank pilot was never finish machined, only fitted to torque converter )

    Oh yeah,, # 4...Enjoy the monster torque !

    Dave
     
    Last edited: Sep 5, 2009
  10. skwurl
    Joined: Aug 25, 2008
    Posts: 1,620

    skwurl
    Member

    My bad I didnt see the Eldorado part.
     
  11. I'm assuming it would be FWD since it's a '76 engine. :confused:
     
  12. I had no idea about the pilot bushing or the flywheel. I need to do more research.
     
  13. zman
    Joined: Apr 2, 2001
    Posts: 16,731

    zman
    Member
    from Garner, NC

  14. Deuce Roadster
    Joined: Sep 8, 2002
    Posts: 9,519

    Deuce Roadster
    Member Emeritus

    How do you figure to mount the Muncie ??

    I do not know of a clutch/flywheel and bell housing that fits a 500 cubic inch Cadillac engine. But then, I am NOT real knowledgeable about the Caddys.

    Inquiring minds want to know. :D
     
  15. I found a website with trans adapter a flywheel and a pilot bushing. It's going to cost about $500 for those parts which is making a th400 look even better.

    m-21 anyone? Trade ya for a bop th400. :cool:
     
  16. Bullrack
    Joined: Aug 14, 2008
    Posts: 336

    Bullrack
    Member
    from Louisiana

    I thought the smaller engines came in the FWD cars. Every 500 I've seen was in a RWD. I have 2 1976 Caddy's. I'm not the authority though, just what I thought. Also, I wouldn't worry about a mild 500 and a Muncie. There were factory big blocks that were stouter than it that had Muncie's behind them. Steven.
     
  17. zman
    Joined: Apr 2, 2001
    Posts: 16,731

    zman
    Member
    from Garner, NC

    all of it is available pretty reasonable. Standard BOP bellhousing.

    40 Ford with Caddy and T56

    [​IMG]

    Transmission tunnel for T56

    [​IMG]
     
  18. I came to realize that the muncie can take the torque, but my wallet isn't quite fat enough to handle the cost involved. I'd rather sell my trans and buy an auto which would hopefully leave me with some extra cash to get the intake and carb. I want. That's the plan, man.

    I did a little searching (all of 30 seconds on craigslist) and found a Pontiac th400 for $200 "rebuilt" and another one for $175 in "great condition" within 20 miles from my house. That's a lot cheaper than the parts required to run the muncie.

    I want to drive my stuff eventually, I'm tired of constantly funding projects that require endless attention. We all know that's not how it goes, but I like to think it can be done where I can drive my stuff someday. Heck, I've been trying to finish my pontiac for 5 years now and the way things are going I may have 5 more ahead of me. :rolleyes:
     
  19. Deuce Roadster
    Joined: Sep 8, 2002
    Posts: 9,519

    Deuce Roadster
    Member Emeritus

    I know about the B-O-P bell housing but the flywheel was my main concern :)
    I know that even in the older ( think 50's ) Cadillacs ... standard shift cars were VERY rare.

    Cool
     
  20. zman
    Joined: Apr 2, 2001
    Posts: 16,731

    zman
    Member
    from Garner, NC

    Last I looked http://www.cad500parts.com/ would sell ya one...
     

  21. I agree.

    Unless you build the Caddy it isn't going to make any more zot than anything else that would have come with the M-21 behind it. I don't see the '39 getting much traction unless you spend either a ton of money or time building a good drag race type of suspension and then spend whats left on tires and VHT.

    granted you can't shift it like the MOPAR Bang-Bang tranny but you can get through the gears pretty quick without out banging them.

    Te 400 turbo would be a good choice if you planned on racing it as would the M-22 but the 400 would cost you less.

    Turbo 350 is probably not a real good choice regardless. They aren't a bad tranny and can be made to be real stout but for money you can do a lot better.
     
  22. Rich Rogers
    Joined: Apr 8, 2006
    Posts: 2,018

    Rich Rogers
    Member

    The Muncie input shaft is the weak link, that's why I didn't put my M-22 behind my 472 Cad. Even when the the performance engines were being built they didn't top well over 500 lbs of torque that the Caddy will deliver. Any BOP bellhousing will work BUT the Pontiac flywheel will not work. Nothing other than the newer ones on the market for the Caddy will fit correctly or safely afaik. Also a T-350 won't last behind it either cause it just isn't strong enough. You'll need the 400 turbo just my .02
     
  23. JeffB2
    Joined: Dec 18, 2006
    Posts: 9,484

    JeffB2
    Member
    from Phoenix,AZ

    Now you could get crazy and swap in the 500 and the front wheel drive if it were narrow enough to fit.I had a 1970 Eldorado that was a lot of fun if you brought it up on the converter and stomped it, it would engulf the front of the car in tire smoke where you could hardly see out the windshield.The '70 Eldo was rated 400 HP@4400 RPM and 550 ft lbs torque @ 3000 RPM, too bad unleaded low octane gas finally killed the 'ol gal.:( Your Caddy with the lower compression and lower HP and torque will probably be more gentle on parts.
     
  24. OldSub
    Joined: Aug 27, 2003
    Posts: 1,064

    OldSub
    Member Emeritus

    Actually '76 is one of the few years the 500 was available in a rear wheel drive car.

    The 500 was originally just in the front wheel drive Eldorado. In the last few years of the 500's use it was also installed in rear drive cars. The reality is its not easy to tell a 500 from a 472 once they are installed and some claim the 472 makes more power.

    I think its more accurate that more high compression 472's were made because they ended soon after '72 ('73 or '74 was the end of the 472) and the low compression bigger motors were installed instead.

    I actually have a '76 rear drive 500 with TH 400 on the floor in my shop today.
     
  25. I still say the Caddy will rip the guts out of the Muncie.

    Like the other guy said, a mild Caddy has much more torque than the average hi perf big block.

    Thank goodness that the TH400 is not only the toughest of the bunch, it is also still the cheapest and easiest option you have.

    Two (three?) strong reasons that are very hard to argue with.
     

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