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Big Block Swap mounts

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by talldogg, Jul 16, 2001.

  1. talldogg

    talldogg 1/2 ton status

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    First of all, I'm seriously pissed at the lack of accomplishment over the weekend regarding my 454 swap. According to me I was already to go Saturday morning. All I had to do was pick up some new motor mounts and a hoist. I know I should be going with poly mounts, but I'm on a budget right now, and besides the 454 is used and it probably won't be the torque monster a built 502 would be. So I got to Auto Zone to pick up the mounts. I know I need big block mounts, not 350 mounts. As I understand, the rubber is denser in the big block mounts.
    First thing that I notice, the mounting holes on the mounts is different from small block to big block. I think I might have been looking at 2WD big block mounts, not 4WD big block mounts. I took home the big block mounts and suyre enough, the holes on the crossmember brackets don't line up.
    Is it possible that I need 4WD big block mounts?? What years did 4WD trucks have big blocks??? Or do the motor mount brackets need to be swapped???
    I stopped by a wrecking yard yesterday to hopefully see for myself, but all I found were 2WD big block trucks and a couple Blazers which I knew were going to have small blocks. Thanks in advance, as I'm dying to finish this swap.

    It's not what you buy, it's what you build!
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Any of the 77-91 K30's should have the proper big block mounts I would think...

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  3. talldogg

    talldogg 1/2 ton status

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    Rene,
    That's what I thought, I asked the guy to look up a 79 4WD 454 K30. The computer didn't show a 454 for this truck, so he looked up 2WD, I think. I can't be sure as he was the one hitting the keys. (Wouldn't it be nice if they just let YOU mess with the computer and have them pull the parts????) Anyway, I'm not sure what I got so I need to find out for sure.
    BTW So does this mean I don't have to swap the motor mount brackets that are on the frame????? Thanks!!

    It's not what you buy, it's what you build!
     
  4. 502Burban

    502Burban 1/2 ton status

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    Talldog,

    I feel your pain. [​IMG] I've recently been there myself. Thought I would need the "big-block" mounts and went through all the same hassles you are experiencing. Turned out I needed to just use the same old "small-block" mounts that were originally in the truck.

    The big-block mounts won't work without fabrication. The difference is in the mounting pattern for the different clamshell housings. I ended up just using the Energy Suspension polyurethane inserts in my original clamshells and everything worked out OK.

    Robb
    '73 GMC Suburban - 502DFI
    <a target="_blank" href=http://community.webshots.com/user/robbrj>community.webshots.com/user/robbrj</a>
     
  5. talldogg

    talldogg 1/2 ton status

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    Robb,
    Thanks for the reply. You would think that the big block mounts would work, but now I'm more focused on what the difference in chassis' is between a 1/2 ton 4wd and a 1 ton 4wd frame. Something doesn't make sense. The difference between a 2wd and 4wd frame is obvious, but what gives between the 1/2 ton and 1 ton??

    It's not what you buy, it's what you build!
     
  6. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    The bolt pattern is different on a truck frame that originally came with a big block motor. If it originally had a small block, you need to use small block motor mounts. The motor side is exactly the same, just the frame side is different.
    Also, the 6.2L used the small block bolt pattern, not the big block pattern.

    Making the world better, one truck at a time.
    SW-ORD
     
  7. 502Burban

    502Burban 1/2 ton status

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    You're welcome. Happy to help. Stephen's got it right (no suprise, there [​IMG]). The frame mounting pattern is different. I figure if the diesel torque-monster can be handled by the small-block mounts, it should handle the big-block torque just fine.

    Robb
    '73 GMC Suburban - 502DFI
    <a target="_blank" href=http://community.webshots.com/user/robbrj>community.webshots.com/user/robbrj</a>
     
  8. talldogg

    talldogg 1/2 ton status

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    Stephen & Robb,
    Thanks guys! By checking out your rigs, I'm confident in what you're telling me. So I take it it's not worth it to look for an original big block 4wd truck and pull the brackets off the frame for my Blazer?? If I remember correctly there are three bolts and one rivet holding it in place. Thanks again.
    BTW I'm seriously overwhelmed by both of your rigs, keep up the good work guys!

    It's not what you buy, it's what you build!
     
  9. white_knight

    white_knight 1/2 ton status

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    They're both right.
    We used small block mounts for our 454

    <a target="_blank" href=http://www.whiteknight.scriptmania.com/>http://www.whiteknight.scriptma
    nia.com
    </a>
     
  10. realsquash

    realsquash 1/2 ton status

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    This jives with my 77, also. I just used stock small-block mounts with my 454, and later upgraded to ORD poly mounts, which bolted right in.

    Squash
    <a target="_blank" href=http://www.trailrunners4x4.org/users/realsquash>http://www.trailrunners4x4.org/users/realsquash</a>
     
  11. 502Burban

    502Burban 1/2 ton status

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    Yup, you have it right on the mounts. There are actually 4 holes in the mount, but only 3 are used to attach it to the frame bracket. The rivets, top & bottom of the mount, are what hold the 2 clamshell halves together, sandwiching the rubber insert between them.

    If you run the urethane inserts, you drill out the rivets, which allows you to separate the clamshell halves. Then just place the urethane insert between the clamshell pieces, and clamp the assembly together with a vise. The inserts come with 2 heavy-duty zip-ties that you slip throught the drilled-out rivet holes. This fastens the assembly together until you bolt it to the frame brackets. After they are bolted down, you can remove the zip ties, or leave them in place like I did. Later, I was glad I left them, 'cause I had to remove the engine again, and the mounts didn't fall apart. [​IMG]

    Good luck! (and thanks for the kind words, too. [​IMG])

    Robb
    '73 GMC Suburban - 502DFI
    <a target="_blank" href=http://community.webshots.com/user/robbrj>community.webshots.com/user/robbrj</a>
     
  12. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    I have a 454, and I used the GM small block mounts... everything fits great, and the engine hasn't even jump out of the truck yet!

    Does anyone else smell BFGs burning???
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s
    <a target="_blank" href=http://24.10.209.54/bigolk5.htm>http://24.10.209.54/bigolk5.htm</a> [​IMG]
     
  13. talldogg

    talldogg 1/2 ton status

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    I want to thank you guys for the replies. You can imagine how frustraing it was for me last week when I realized I wasn't going to be able to drop in the big block. I had bought the BB mounts at Auto Zone without being sure if they were the right ones, I stopped by Kragan and they couldn't figure it out either, I was really dissappointed when the guy at Napa couldn't figure it out and mounts his book listed were the EXACT same mounts I bought at Auto Zone, just in a different box. As for now I'll just take back the BB mounts and buy the SB ones. The engine is used and I'm not too sure what shape it's in, so the regular mounts should be fine for now. I'll just keep an eye on them and if they need replacing, I'll swap them, or if the engine ends up needing a rebuild later on I'll swap to the poly ones. Thanks again!!!!

    It's not what you buy, it's what you build!
     

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