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Big Block vs. Small Block Motor Mounts....w / PICs...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Greg72, Dec 6, 2001.

  1. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Ignorance is bliss....I never cared about motor mounts until I started learning that there is something strange about the way my motor is installed.....

    It's a big block motor....but I'm told it's is installed using small block motor mounts and crossmember. Is this a common thing? Also...there appear to be two sets of mounting holes in the frame for the crossmember. The rearmost pair would seem to be for the smallblock motor, and the more "forward" pair would seem to be making a bit more room for the big block by bringing the motor away from the firewall.... [​IMG]

    Right now the motor is pretty tight up against the firewall, with minimal clearance for the distributor and valve covers. If it's possible to move the crossmember to the "forward" holes, I'd gain about 2 inches of additional clearance back there.

    I've posted photos in my CK5 album to show you more clearly what I'm talking about. Please check them out here:

    See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38
     
  2. Blazer79

    Blazer79 1/2 ton status

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    I don't think you can move the engine to the other holes because you would pull the torque converter from the tranny (or not be able to bolt it to the flexplate). My 454 bolted exactly to the same holes as the SBC. There were no more holes. I think engine mounts are standard distance from the tranny so you can bolt in any Chevy engine.

    <font color=purple>//////
    <a target="_blank" href=http://blazer79.freeyellow.com>blazer79.freeyellow.com</a></font color=purple><font color=black>
    Soon a 454 K5!!</font color=black>
    [​IMG]
     
  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Ok,

    Just to clarify.....I understand that moving the engine would also mean moving the transmission/xfer case and rear crossmember too......and also some driveshaft length issues.

    I am not trying to keep everything else in it's current position and simply pull the engine forward.

    Thanks for bringing that up though, I want to explain this as clearly as possible. [​IMG]



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  4. Emmettology 101

    Emmettology 101 3/4 ton status

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    It is possible to do, but one good thing about having it set back is a better center of gravity!(Not much, but some)

    But I dont see why ou couldn't move everything forward and redrill the t-case crossmember mounts..... You'll have to adjust the shift linkage probably also!

    Mike

    <font color=green>"1024x768x256... Sounds like one mean woman."</font color=green>

    <a target="_blank" href=http://www.geocities.com/emmettology101>www.geocities.com/emmettology101</a>
     
  5. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    As far as I know all trucks, small or big block, used the same motor mounts. I do know that late '60s and early '70s Camaros and Novas had different motor mounts for small and big blocks. The big block mounts were a little taller to clear exhaust and oil pan. They didn't make any difference front to back. I know for a fact that you can pull a small block out of a truck and bolt a big block right back in its place without any changes to the motor mounts. I would say that you have got it right. Hope this helps.

    '85 K5 : Run it til it breaks, then fix it and go again!
     
  6. four_by_ken

    four_by_ken 1/2 ton status

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    I agree... big block, small block the same. Pull out drop in... Did it, done it.

    Ken H.


    '86 K5 up and coming
    14 bolt(Detroited),10 bolt,39.5 Boggers rear,
    TSLs front, 468 BBC, 350 trans, 205 transfer
    Rust free in Michigan!
     
  7. michaelm

    michaelm 1/2 ton status

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    you are only showing the easy side.
    the crossmember is a bunch trickier on the other side
    does it also have extra mounting holes?
    how about bottom of the frame rail?
     
  8. Triaged

    Triaged 1/2 ton status

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    I have that set of holes too but no matching holes on the under side of the frame (or for the t-case crossmember).

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  9. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    OK, here's something I didn't know.....I guess Chevrolet used the same motor mounts for the 327/350/396 blocks.... even though the 396 is a BB, they still used the same attachment bracketry and mounts.

    The 454 is apparently a different animal, and totally different mounts.

    So I guess nothing unusual is going on from that perspective. I did check the opposite framerail as someone suggested.....there are some holes, but clearly NOT the same offset pattern like on the drivers side. The motor could be pulled forward those couple of inches, but I'd have to drill some holes to accomplish it.



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  10. LKJR

    LKJR 1/2 ton status

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    Someone find this man a job, WAY too much time on his hands......

    Like em big and topless
    Excuse me...Would you mind removing your import from under my chevy?
     
  11. Sparky87k5

    Sparky87k5 1/2 ton status

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    I swapped out a 6 cylinder engine / 3 speed manual trans for a 327 / 4 speed M21 trans in a 68 Chevy pickup 1/2 ton shortbox many years ago that had the same mounting holes as your pictures show. At the time I had to move the frame mounts from their original holes to another set that were already in the frame. It seemed that one set was for V8 and the other for 6's. Not sure if this applies to 72 K5's but possible.

    87 K5, 427BBC,D60 & 14BFF, NV4500, NP208, TSM disc's,
     
  12. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    There is something else no one else mentioned. What about clearance issues with the crank damper and pulley? The front cross member is in front of the pulley on my 454 only by 1/2" or so (using the SBC mounting locations). So if you move it forward you may risk some kind of interferrence issues with those parts! [​IMG]

    I would just leave it in the SBC locations. Thats where mine is installed, and I see no use for the additional 2" or so space at the firewall... Those engineers at GM do know what they are doing time to time!!! [​IMG]

    My .02!

    <font color=red>GOT MUD???</font color=red>
    My license plate reads:<font color=blue> 8 YR SUV</font color=blue>
    Excite @Home SUCKS!
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s
     
  13. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Sparky,

    Actually, that's a VERY good point! There was never a big-block offered on the 1st Gens....the biggest motor was a 400SB. A 6-Cylinder was the base engine, so maybe that's what those extra holes were for.



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  14. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    From what I can remember from swaps and motor pulling. The same points are used on the frame for all V8's small or big block. As stated the same mounts were used for all small blocks and the 396 big block. The 454 (and posssibly the 427, which I have never pulled out of a vehicle, so I am not sure, but could be the same as the 396) however used different rubber mounts and "clamshells" (and maybe a slightly different frame mount (can't remember now), but they all used the same frame holes. The extra set on some frames (from what I was told by a GM truck mechanic) was for the inline sixes which were even used in 1/2, 3/4, and some 1-tons. Again this is not the word of LAW, but it is true to the best of my knowledge with numerous engine swaps my friend and I have done.

    See my rig at <a target="_blank" href=http://coloradok5.com/gallery/Leadfoot> click here </a>
     
  15. RGF

    RGF 1/2 ton status

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    I think the extra frame holes does have something to do with using an inline 6, I dont know anything about the 72 frames but I put a 292/6 in my yard truck(85 1ton) the right side mount had to be moved fwd because of the mount off-set on that motor. The holes were already there in the frame and it was a bolt in and didnt have to do anything with the crossmember, I think that they used alot of those 292s back in the early 70s.

    RGF
     
  16. LKJR

    LKJR 1/2 ton status

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    Greg,

    I don't know what was offered in the blazers as engine options but in the trucks the inline mounted in the rear most position and the small block mounted in the front set. Guys take and use the inline mounts for the small blocks on street trucks to gain a little CG advantage, Does hug the firewall a lot but it works, But I think the blazers are different......

    Like em big and topless
    Excuse me...Would you mind removing your import from under my chevy?
     
  17. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    That seems true.
    Greg- do you know what engine originally came in your K/5?
    Was it a small block?
    You can tell by the Vin # and your LMC catalog, or I have one if you tell me the vin.
    Ryan
     

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