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Older block in a '90????

Discussion in 'The Garage' started by tiger9297, Sep 8, 2006.

  1. tiger9297

    tiger9297 1/2 ton status

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    I am planning an engine swap in my '90 K5. I had plans to do a BBC or maybe a 400 SBC. However, a guy told me yesterday that you cannot put an older block in my truck b/c the older blocks do not have the "crank sensor" (????) that tells the computer when to fire. I have never heard of this. I know tons of people have put 406 SBC's in trucks but I'm not sure if it has been done in the computer controlled models or not. Anyone got any knowledge of this?
     
  2. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    Crank trigger! Have you previously swapped in a LT1 engine or something like that? Something with an Optispark? That's about the only way you wouldn't still have a regular HEI distributor sticking up at the rear of the engine.
     
  3. tiger9297

    tiger9297 1/2 ton status

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    No I haven't swapped in anything. I have just pulled the original TBI 350 out of the truck. I am trying to plan out the new engine and I was considering a 400 SBC. Then I talked to this guy yesterday and he said it couldn't be done. I always take "advice" I get from people with a grain of salt til it's confirmed by the folks here at CK5.

    So you are saying that I CAN swap in an older 400 SBC and use the stock computer without any problems?
     
  4. K5er4Life

    K5er4Life 1/2 ton status

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    you can, the TBI engines dont have any crank sensor, theyre a very simple fuel injected setup that doesnt require a whole lot to run. However, there are going to be some things you need to consider when putting together a TBI 400. A few things that come to mind off the top of my head are as follows...

    1. Bolting the TBI to a stock style 400 intake will not work unless you use a adapter readily available at jegs, or summit, wherever. You cant bolt a TBI intake to the 400 heads because the bolt pattern is slightly different. I have heard of people modifying a TBI manifold to fit the old style heads but I have no experience with this.
    2. Youll want to obtain a cam that will be appropriate for a fuel injected motor. The cam designed for a carb motor will have a lobe seperationa angle and a duration that the TBI system will not particularly like or run at its best with. I would talk to a few cam manufacturers about what will be best with the heads and setup that you are using.
    3. Figure that with the displacement of the 400, presumably the cam will be different than the stock TBI cam, youll need to to a little prom work. I got my chip from TBIchips.com. It worked ok but there is some tuning for me to be worked out still.


    Thats all I can think of right now on the spot, there is more but thats the jist of what youll run into. TBI systems are very simple and are easy to hook up. Theres not alot of wires or sensors but without the right combination of parts it wont run very well. Dont expect that you wont have to do a little bit of tuning because I imagine once you get everything in there (400 sized motor, nice cam profile, etc..) you will have to play with the computer to get it to run at its best. Im sure someone will poke in here with some things that I forgot but right now I have to get back to work, after I look through some other posts real quickly. :D
     
  5. GMCJason

    GMCJason 1/2 ton status

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    I had a similar question a while back but I was just looking at an older 350 block, not a 400. Here's the link.

    http://coloradok5.com/forums/showthread.php?t=143688

    I haven't done anything with this yet so I can't speak from experience but it appears you should be OK using the block. I agree with K5er4Life on the computer stuff; you'll need to get a new chip.
     
  6. b454rat

    b454rat 1/2 ton status Premium Member

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    Tell that guy is he full of sh!t. I had a TBI 406 in my old truck. Block was a 73, heads and up were 88-up. You can even run the older heads, just need to elongate the center bolt holes.
     
  7. bleedchevy

    bleedchevy Registered Member

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    When you elongate the center four bolts make sure you black permatex the heck out of the holes to help seal them. I put a 79' block in a 88' worked just fine.
     

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