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1990 Small Block to Big Block Conversion

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by blazen_md, May 21, 2003.

  1. blazen_md

    blazen_md 1/2 ton status

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    Looking to put a big block in my 1990 blazer that already has a tbi 350. I want to keep my fuel injection and use an early 90's 454. I talk to Turbo City today and they said all I would need is the big block throttle body and I would probably have to use one of their chips in my computer everything else should work from the small block. Has anyone done this and I would like to know any other problems that you have come across etc. If it matters I will most likely be using a TH400 transmission. Thank you for any help.
     
  2. BlazerGuy

    BlazerGuy 3/4 ton status

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    You may need to upgrade your cooling system to a 4 core(or a big 2 core) radiator and all the bracketry(alt, PS etc) will have to be from the BB.
     
  3. the cork

    the cork 1/2 ton status

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    youll also have to fiddle with your exhaust, to what extent
    i dont know, for sure the manifolds need to be big block, after that the y pipe might line up or not,
     
  4. fortcollinsram

    fortcollinsram 1/2 ton status

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    I just dropped in my rebuilt 1992 454 TBI into my 1987 K5 the other day...I bought the 454 complete with all the accessories, TBI, wiring harness and computer...You can reuse you existing harness but you will need to swap a couple connectors here and there (most notably, the TPS, and IAC and such on the throttle body)If you are going to keep the 454 pretty stock just find a 454 TBI ECM and swap in the entire computer or just the PROM...you can get these for like $30 from a yard...I wouldn't waste $$$ on a custom chip that was available from the factory /forums/images/graemlins/wink.gif Although if you do get a factory 454 TBI ECM or PROM, make sure if was from a truck that either had a 5-speed or a TH tranny...if the truck that the ecm is from was equipped with a 4l80E, the ECM and PROMS are different and won't work... /forums/images/graemlins/thumb.gif

    For the the biggest pain has been clearance issuse with my headers...the headers cut it too damn close in areas like the knock sensor and fuel lines...but with stock iron mannies, you'll be fine..

    I second the radiator idea...I just tossed my leaky stock 2-core and bought a NEW 4-Core Modine for $170...

    Other than that, fuel lines are the same size (I bought new ones for the 454 b/c the hard line in beat to accomodate the dist., coil, etc.) spark system is damn near identical...

    Chris
     

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