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small block to big block swap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by slider, Jul 14, 2003.

  1. slider

    slider 1/2 ton status

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    I am putting a big block in a 1984 chevy 4x4 that had a small block in it. Upon install I have noticed that their is no room between the brake power booster and the valve cover. If I had to change the valve cover I will have to pull the booster. I see where they make short valve covers but I am running studs and roller rockers and they will not fit under short covers. I used small block mounts and it all fit fine. Does the big block use different block mounts that attach to the frame? Anyone else have this problem after a swap? Thanks for the help, and p.s. this thing hauls ass now /forums/images/graemlins/thumb.gif
     
  2. fortcollinsram

    fortcollinsram 1/2 ton status

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    Yeah, that is the reason I wen't with roller TIPPED rockers, so I could use the factory short valve covers...It is a really tight fit...You can hammer a stamped stell valve cover to fit...I am running factory cast aluminum covers on mine and I can still get the valve covers on and off with out touching the PB booster.... I say live with it If I already had the full roller rockers and the tall valve covers I would just keep it... I mean, you really don't pull your covers except to adjust valves and replace the valve cover gasket....

    Chris
     
  3. Zeus33rd

    Zeus33rd Smarter than you GMOTM Winner

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    Hmm...

    I've got Harland Sharpe full roller rockers on my big block with the tall covers...No issues getting the covers off here. Its not exactly a strait up and off deal, but nothing difficult about it.

    [​IMG]
     
  4. morphed86k10

    morphed86k10 1/2 ton status

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    Time for hydroboost /forums/images/graemlins/thumb.gif
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Orange intake? /forums/images/graemlins/smile.gif
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    I see where they make short valve covers but I am running studs and roller rockers and they will not fit under short covers.

    [/ QUOTE ]

    Did you *try* this though?

    I have a motor that supposedly won't fit roller rockers under the stock valve covers. But the problem wasn't the valve lift, (which CAN be an issue if you have a lot) it was the studs and polylocks. So, I took the studs out, cut a few threads off the top, then took the polylocks and cut most of the head off of them. (the part that has the wrench flats, you don't torque them much, so no problem removing a bunch of material there)

    That way, by cutting the stud AND the top of the polylock, there are still plenty of threads left in the polylock on the stud, and the set screw still sits flush. Couldn't do this if we were talking 1", but I took off a bit less than 1/4", and all was good.

    Just an idea if you really want easy to remove valve covers.
     
  7. Zeus33rd

    Zeus33rd Smarter than you GMOTM Winner

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    [ QUOTE ]
    Orange intake? /forums/images/graemlins/smile.gif

    [/ QUOTE ]

    Its orange cause its the stock cast iron POS, Ugly as hell un painted. /forums/images/graemlins/pimp1.gif
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    Its orange cause its the stock cast iron POS, Ugly as hell un painted. /forums/images/graemlins/pimp1.gif

    [/ QUOTE ]

    Ahh, I understand. At least you've got a big block. /forums/images/graemlins/smile.gif

    I didn't even bother to paint my new engine. It's just got your typical 23 years of sludge on it. /forums/images/graemlins/smile.gif
     
  9. slider

    slider 1/2 ton status

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    Thanks for the info but the question remains the same. Are the big block engine mount brackets that bolt to the frame different from a small block? And if I do install the big block frame mounts willthe motor drop down and I will have clearance between the booster and the valve cover. The problem is the motor under heavy load hits the valve cover, it has new motor mounts and a new transfer case mount. Thanks for the help.
     
  10. madmike

    madmike 1/2 ton status

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    I don't know the answer to your question, but I would like an answer too. I just swapped a big block into my truck that had a small block in it. The engine fit fine, no problems, but my tranny was still 3/4" away from final fit. If I tried to shove the engine back, it hit the firewall. I ended up drilling 4 new crossmember holes in the frame and moving the tranny forward.

    The odd thing about this is that I pulled the big block from another truck I had, which was exactly the same year, frame, etc. I still don't know why/what was bastardized!
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    The mounts are all the same.
     
  12. morphed86k10

    morphed86k10 1/2 ton status

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    No no no no!! The mounts are not all the same!!


    Ok, it depends on what you are calling the mounts really. Everything that is originally rivited to the frame is basically the same for all intents and purposes. The "cradles" (I don't know the real name), i.e. the shells held on to the motor with three bolts per side are different from original small block to big block trucks.

    I had this problem when I put my 454 in my K10 from my K30. Everyone said the mounts are all the same. I pulled the two motor mount bolts from the K30 and pulled the 454 complete and tried to drop it in the K10, but it just wouldn't go. After a while I swapped the cradles from the old small block on to the big block and it slid in just right. I'd bet thats the same problem you're having.
     
  13. Sparky87k5

    Sparky87k5 1/2 ton status

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    Having completed the SBC to BBC swap I do know that SBC motor mounts bolt to a BBC and then allow the BBC to sit on the SBC frame mounts. My trans bolted right up to the bellhousing and my SBC clutch/TO bearing all swapped over to the BBC flywheel. I'm using the GM cast alluminum valve covers (late 454/502 style), stock rocker arm/valve train and am able to remove the valve covers w/o problems. Tight fit but they come off.
     
  14. slider

    slider 1/2 ton status

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    I found a set of frame cradles today they are different from the small bock to the big block, the big block ones will let the motor set a couple of inches lower. Thanks for the help.
     

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