BRAKE DRUM QUESTION.

Discussion in 'Got gears?' started by 70skylark350, Sep 17, 2017.

  1. 70skylark350

    70skylark350 Jesus loves you unconditionally

    Hi, wondering if anyone knows if a 3987445 n.o.s. brake drum would be the same as the ones for my 1970 8.2 Buick rear? they are listed for 70-72 chevelle and 74 nova.
     
  2. 70skylark350

    70skylark350 Jesus loves you unconditionally

    I did a google search, I may have answered my own question? this part number comes up as a front drum so this will not work for my rear correct?......... Man what the heck did we do before the internet.....lol.
     
  3. monzaz

    monzaz Jim

    The Buick rear drums are different as they have a larger finned skirt that goes past the backing plate offset. Chevy only goes up to the backing plate.
    Just another one of those Buick Olds added extras for more cooling etc.


    BUT physically the Pontiac and chevy drums will work - Pontiac will be the best fit as it has the correct hub register (2.78) and stud holes Chevy has a 2.81 hub register and the same stud holes 7/16 x 20

    Jim J D Race
     
  4. 12lives

    12lives Control the controllable, let the rest go

    Hi Jim - hub register? Please explain:
     
  5. monzaz

    monzaz Jim

    wheel and drum are centered on the hub register. part that sticks out in the middle of the axle shaft wheel bolt pattern
     
  6. 12lives

    12lives Control the controllable, let the rest go

    Thanks - interesting. So with the chevy drum the drum could be slightly off center and cause a vibration or uneven braking? Have you (or anyone?) run across that?
     
  7. 70skylark350

    70skylark350 Jesus loves you unconditionally

    huh, yes very interesting information. I never would have guessed. Thanks for the info. so a chevy drum will fit a Buick but a Buick drum will not fit a chevy?
     
  8. monzaz

    monzaz Jim

    correct. And you can fit a BOP drum on a chevy you just need to open up the register hole with a deburring bit on a grinder etc. Just ream it around .

    The part stores are selling 8839 drums for all the old cars and they are just not correct they are for metric stud rears from 1982 -2004 etc. YOU can use them but the studs are sloppy and the hole for the register needs to be opened up again.
     
  9. 70skylark350

    70skylark350 Jesus loves you unconditionally

    so where would a guy buy factory correct drums? OPGI?
     
  10. monzaz

    monzaz Jim

    regular part stores have them they just need to work harder to find them. :) Jim
     
  11. flynbuick

    flynbuick Guest

    I will be you a Diet Coke that OPGI does not realize there are any differences among the drums.
     
  12. monzaz

    monzaz Jim

    scary if they do not...
     
  13. flynbuick

    flynbuick Guest

    I remember my first experience with OPGI. I saw they had an aftermarket distributor listed for a Buick 455. I called them a couple of times before I purchased to verify the application because at the time no one else had one for a Buick. Yep, they checked it out and they were sure it was for a Buick. When I received the unit it would not fit. I determined it was for a Pontiac 455. I called OPGI and of course OPGI thought BOP 455s are all the same.
     
  14. monzaz

    monzaz Jim

    LOL. That is funny cause it is the SAME thing with REAR ENDS... not ALL bop 8.2 ARE THE SAME.
     

Share This Page