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305 vortec swap to 350 vortec

Discussion in 'The Garage' started by sniderman, Jun 13, 2005.

  1. sniderman

    sniderman Newbie

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    I have a 98 GMC 1500 that had a 305 vortec and I installed a new 350 vortec long block,I used my old intake ,computer ,sensors,&wireing.its running fairly good.but has a little hesitation.no codes are showing up. Is there anything that needs to be changed.


    Thanks for any help SNIDERMAN..........
     
  2. sled_dog

    sled_dog 1 ton status

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    Chip and maybe center injector. The Fuel trims likely just can't keep up with the 350. Its likely running lean most of the time but not so much that the PCM senses a big problem.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Timing is likely also another issue where the 305 and 350 are different.

    Calibration of the chip as mentioned is more than likely part of the fix.
     
  4. sniderman

    sniderman Newbie

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    chip

    how do I go about getting the chip programed.and excuse me for asking a dumb questionbut is the chip located in the computer under the hood.Sorry but I'm not real famialar with the newer engines.

    Thanks SNIDERMAN..........................
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Unfortunately neither am I. It's OBD2, I know very little about those systems as a whole.
     
  6. sled_dog

    sled_dog 1 ton status

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    I know a lot about the function of the systems but little about the specifics on that model. www.fullsizechevy.com has lots of guys with that body style truck. Someone there should be able to help you out better.
     
  7. sweetk30

    sweetk30 professional hooker Premium Member

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    gm dealer to re flash the computer most likly. and the timing is not like other old stlye setups. you need to have a scanner to set the timing. you need to watch for a set point in the read out and turn the distributer till it hits that point and lock it down. hope this helps ya. good luck.
     
  8. sled_dog

    sled_dog 1 ton status

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    The point where the crank reference signal indicates #1 cylinder. Its a good point that GM dealer should be able to flash to the 350 setup.
     
  9. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    Just get a complete PCM from a junk yard. I paid 65 bucks for one out of a 96. This would be much cheaper then having someone re-flash it. Then you really need new injectors and they can be pricey!

    Mike
     

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