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BBC into gen 1 k5. Crossmember built

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by MNorby, Oct 2, 2006.

  1. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    Going to put the 454/ TH400/ Doubler into the 71. It is currently in an 83 frame. What do I need to know about motor mounts? Will the ones from the 83 fit? Crossmember clearance? It has HEI and tall valve cover to cleare roller rockers. I am putting a 1" body lift on the rig. Will I need to do some creative BFH mods to firewall to fit it? It also has hedman headers, will they fit? Looking in a jegs mag it looks like the application could be the same. Any other tips regarding the swap?Thanks
     
    Last edited: Oct 9, 2006
  2. bigblock72

    bigblock72 1/2 ton status Premium Member GMOTM Winner

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    Move the front crossmember forward about 2 inches and that will cure your firewall issues, just make sure you check clearance to the radiator, but somewhere around 1-2 inches makes a big difference. Use the first gen motor mounts, they will bolt up. Headers may work, you may have to space the mounts up a half inch to make the tubes clear the crossmember.
     
  3. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    I have read alot about using 73 and newer truck engine crossmember, did you do that or just take the stock one and move forward? I will also use the 4 core radiator and prob continue to run electric windstar fans
     
  4. Yukon Jack

    Yukon Jack 1/2 ton status

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    Burt4x4 used the 73-up crossmember and had just minimal firewall mods to make - he has a body lift. I used the stock crossmember and had to do considerable firewall mods. If you move the engine forward, keep an eye on your front driveshaft angle to make sure it doesn't get too severe. Keep us posted and be sure to post pics of your swap.
     
  5. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    front shaft shouldn't be too much deal being as going doubler so moving forward will help rear shaft angle. What about full length header clearance with the stock crossmember?
     
  6. Yukon Jack

    Yukon Jack 1/2 ton status

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  7. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    does anyone have pics of normal 73-87 type headers in the gen 1 rigs with the 73-87+ type crossmember installed? hang down issues?
     
  8. bdozeraz

    bdozeraz 1/2 ton status

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    we put a big block in my dad's 71 and had no real issues. Used the stock low boy valve covers and it cleared the fire wall. used the stock 71 crossmember in the stock location with the stock 71 motor mounts and everything bolted up.
     
  9. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    bdozeraz, what did you have for exhaust?
     
  10. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    well got then 350/465/205 out this weekend and got my 454/th400 out of the other rig and ready to strat the swap. I want to move the engine forward an inch or so forward for firewall clearance and driveline lengths. Here are the 80s style engine mount towers bolted in the frame with the center of mounts roughly 1 inch forward. I messed around with the 80s style crossmember but it looks like a hack job to use it so gonna build something like this out of 1.5x3/16" sq tube. Opinions?

    I already have the scale blueprints drawn out. Should have 1" clearance from oil pan. This drawing was just for visiual aid.

    crossmember.jpg

    crossmemberedit.JPG
     
  11. CDA 455

    CDA 455 3/4 ton status

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    If you can, try moving the axle forward the same amount (1 in) to stay 'neutral' with rig balance.
    Ideally though, the engine should be behind the front axle (i.e. engine pullies should be at, or behind, the front axles.
    Good luck and keep the pics coming :D !!
     
  12. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    i have already moved the front forward 1.5" with a zero rate and will prob a little more when I do 52s in the front
     
  13. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    crossmember built

    crossmember built out of 1.5" 3/16 sq tueb, just need to make mounting provisions.

    crossmembernew01.jpg
     
  14. RGV72BLAZER

    RGV72BLAZER 1/2 ton status

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    looks beefy.
     
  15. Clockwork71

    Clockwork71 Registered Member

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    I think with the new motor mounts you should be able to run any 73-87 headers with little or no frame mods. I kept the original crossmember and motormounts and used doug thorley 304-y headers. I had to grind the frame for the second header tube on the pass. side. I would recommend using short valve covers if you can. You will have less firewall clearance issues. Also, i think your box steel engine crossmember will work good. it looks like you won't have any clearance issues if you use crossover steering.
     
  16. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    I am using my ord crossover steering from my buggy so it already has a bent draglink but it will clear by a mile. I have to run tall valve covers because of my roller rockers. Found out the hard way when I put the engine in and was putting the tin on the stockers wouldn't clear.
     
  17. Yukon Jack

    Yukon Jack 1/2 ton status

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    Very clean looking crossmember. You do great work.
     
  18. vtblazer

    vtblazer 1/2 ton status GMOTM Winner

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    :bow: :bow:
     
  19. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    works on more tonight but didn't have time for pics. drilled my7/16 holes that bolt it to the engine mount brackets out to 7/8 and put some bushing material in there so when the bolt it tightened down it will be tight against the bushing instead of trying to squeeze the tubing together. Will take pics tomarrow.
     
  20. bigblock72

    bigblock72 1/2 ton status Premium Member GMOTM Winner

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    That crossmember looks great! Quite impressed with how it turned out. The later style motor mounts are ton stronger than the early style, I think the motor should fit nice with what you're doing.
     

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