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Big Block Swap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ledfoot, Dec 17, 2000.

  1. ledfoot

    ledfoot Registered Member

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    Has anyone swapped a small block for a big block? How hard is it? Will I need different motor mounts. Also, I have a 700R4, will I need to do anything with it, like move it forward or back.
     
  2. BigJim85

    BigJim85 1/2 ton status

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    I believe just about everything bolts right up. You'll need a bigger ratiator, just go to a junkyard, or a shop, and get a radiator from a Suburban with a 454 in it. That bolts right in too. I dunno what year yours is, but my Dad put a 454 in a '83 with no trouble, like I said, it all bolted right on, might be different in later years. I'm not sure about moving the tranny though, my Dad didn't but his was a stick.

    <font color=red>If it's stupid but works, it isn't stupid.</font color=red>
     
  3. MudFrog

    MudFrog 1/2 ton status

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    Be careful about putting a big block infront of a 700R4. You might want to look into beefing the tranny up some.

    89 K5 Silverado
    http://mudfrog.coloradok5.com
     
  4. bablazer73

    bablazer73 1/2 ton status

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    I am putting a bigblock in my blazer. after much research, I have found alot of money would have to be spent on the 700r4 to make it "reliable". we all know these trannys are weak, and much money is needed to make them stronger. I have decided just to use a th400. I would like to have kept the 700r4, but nobody could make me believe it would last. I hate being broken 20 miles in. THAT SUCKS!!

    your right. I don't understand the jeep thing!
     
  5. baldbandit

    baldbandit 1/2 ton status

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    I'm looking at using this kit in my 700r4 and planning to build a 489 stroker. The tranny is rated for 600 hp and the 489 is rated at 580 hp and 600# torque. Anybody use this kit in their tranny? http://www.transmissioncenter.net?highperf700r4.htm


    baldbandit
     
  6. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    you're back to the old question of "wind it tighter" or "let it loaf". Spending the money on the 700 will probably work, there are a lot of shops that know what they're doing with them, but along the same lines, why not just build the heck out of a small block? because you'll spend more money and put a lot more stress on the parts than you will with a big block. it's the same way with a trans, do you stress the heck out of the 700 or loaf a 400. i say loaf the bigger trans, that way any material defects in any of the parts will not be as likely to show up. The big problem is lack of a low 1st gear and overdrive. Not much you can do about that.
    good luck

    [​IMG]
    SW-ORD
     
  7. nyyef

    nyyef 1/2 ton status

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    you could always try the 4L80, the overdrive TH400. i have been thinking about this swap, but over here big blocks are hard to find. i am debating between a big block or a nice revving 383 for sand dune abuse...i mean...use.
    but i have a 4spd SM465....will the bellhousing bolt right up?

    Knife.
    knife.coloradok5.com
     
  8. Burt4x4

    Burt4x4 3/4 ton status

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  9. nyyef

    nyyef 1/2 ton status

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    thats what i was thinking, because i already have a healthy 350 in my other k5. all i need is the stroker kit. can anyone recommend a company that sells a complete...i mean COMPLETE kit? something that i dont have to balance or machine....just clean and bore the block and install.

    Knife.
    knife.coloradok5.com
     
  10. Burt4x4

    Burt4x4 3/4 ton status

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  11. HarryH3

    HarryH3 1 ton status Author

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    You'll need to get all of the accessory brackets to fit a big block. The ones from your small block won't fit. This is when it's nice to get a complete take out engine from a donor vehicle. It will have all that stuff with it.

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  12. loudandproud

    loudandproud 1/2 ton status

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    What do you have to do to make your 350 a 383??? What do these kits do?? What is involved in putting them on??

    Thanks
     
  13. grtwhite

    grtwhite 1/2 ton status

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    Anyone know how much a 4L80 cost? Just wondering, thanks - Jay
     
  14. nyyef

    nyyef 1/2 ton status

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    simply a 383 is a 350 block 0.030 over and a 400 SB crank. thats it!!
    installing a 4L80 can be expensive because you need the computer thingy....JETperf sell them for astronomical prices. but i have heard you can get the same computer thingy from a diesel truck....or something.....anyone wanna add some more accurate info?

    Knife.
    knife.coloradok5.com
     
  15. You also need new pistons for the diff in stroke.You also need the flywheel/flexplate for a 400/externaly balanced sb.
    And the harmonic balancer for the same application.The 4L80E
    is alot doe,your probably talking $3000 for the thing!!I'ld do a NV4500 conversion and save a few bucks,nothing like a stick anyway.The best thing about a big block swap is you can run a stock reliable motor and have plenty of power,on trail rigs the more reliable it is the beter you are.Just my $.02,good luck.
     

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