1980 GMC High Sierra questions

Discussion in '1973-1987' started by Dennsco, Jun 23, 2014.

  1. Dennsco

    Dennsco Member

    Jun 23, 2014
    Conifer Colorado
    Greetings, I am new here and appreciate all the knowledge on this forum.

    I recently purchased a 1980 GMC High Sierra shortbed 4x4 as a basket case, mostly the engine and engine compartment needs to be reassembled. The previous owner said it had a good 305 installed with all new gaskets so I will need to reinstall all of the components, alt, power steering pump, fan, shroud, etc:, but not sure if everything is there yet as I have several boxes of parts.

    My questions are, what would I need to do to maximize HP Torque from the 305? I realize it is a smaller motor than the 350 that originally came with the truck and am a little concerned it will struggle with the 4x4. I also do not want to dump a lot of cash and time either and would prefer to stay with the current motor. I was thinking a cam, and new intake/carb setup? Headers or stock mani's? I will need to put in new exhaust from front to back, so dual turbo mufflers or single?

    What would be the suggested carb setup for this motor? How about a tpi retrofit? Worth it?

    Also, I live in Colorado, and we do have an air program here so I would need to be sure it meets emissions standards, not sure if I need air injection, cat, or what would be required.... seems a little daunting the task before me but if anyone has any advice that would be greatly appreciated!
  2. Ben@CPOA/TECH

    Ben@CPOA/TECH Member

    Oct 26, 2013
    Kansas City, MO
    You can certainly hop up your 305 a bit and have plenty of power to spin all 4 wheels. Any fuel injection setup tuned correctly will give you more power than a carb with vacuum advanced ignition.
  3. Pontiac1976

    Pontiac1976 Member

    Aug 21, 2006
    Ontario, Canada
    Make sure the valve guides are good or you could burn the pistons blow block. When there the valve seals could be done.
    CAM, Intake alum, 4BBL carb- or as said fuel injection setup, Flat top Pistons
    your choice but you will have to make sure it meets emissions standards for the part you replace. OH good balancer
    It might be less work to keep the carb set up.
    That if you stay with the 305 keep clean proper oil changes it should last.

    If your going to work it really hard not keep on the on the oil changes a 350
    will be a little better for hp

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