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Which block head combo

Discussion in 'Chevy Trucks' started by jlwhite90, Nov 6, 2003.

  1. jlwhite90

    jlwhite90 Junior Member
    from Florida
    Messages: 3

    Hi all.
    I have an 86 GMC C1500 VIN# IGTEC14H8GF734587, currently sporting a 305, starting to get some mileage on her and I would like to swap to a 350.
    This is used as a daily driver, possibly towing a small boat on occasion. I don't want a race truck, but when I step on the gas I want her to answer nicely.
    I have 2 blocks (350) to choose from as well as 3 sets of heads, one of which are on the 305.
    Block #1 p.n. 3970010
    Block #2 p.n. 14093638
    Head#1 p.n. 14102193
    Head #2 p.n. 462624
    I also have the crank to both blocks.
    Which combo to use??? Any help would be greatly appreciated.
     
  2. TomatoRedGMC

    TomatoRedGMC Member
    Messages: 39

    :salute: welcome!

    I don't know alot about the head PN's, but do know that the block #1 you have listed is of a 350, while #2 is most likely a 305 block. from past experiences here, i've been told to try and keep 305 heads with 305 blocks, and the same for a 350....mixing and matching may cause compression problems....here is a great website to identify your parts better.
    Apparently, #1 is from 69-79, a 350, can be a 2 or 4 bolt main.

    http://www.nastyz28.com/sbchevy/sblock.html#casting

    this should help you get a matched set.

    walt

    :drinkup:
     
    Last edited: Nov 6, 2003
  3. TomatoRedGMC

    TomatoRedGMC Member
    Messages: 39

    Last edited: Nov 6, 2003
  4. wyldman

    wyldman Member
    Messages: 3,265

    Use the 3970010 block.It's most likely a 350 (could be 327) high nickel block,very strong,and may have 4 bolt mains.That block is worth some $$$ if it's a 4 bolt.You may even consider selling it if your not building a high HP motor.

    You can use the 305 heads on a 350 for about a 1 point jump in compression,and the smaller valve sizes will help the bottom end.
     
  5. jlwhite90

    jlwhite90 Junior Member
    from Florida
    Messages: 3

    the 3970010 block has 2 bolt mains so I think I'll just keep and use her. Thanks for the input, and please keep it comming.
     
  6. wyldman

    wyldman Member
    Messages: 3,265

    You can add 4 bolt mains if you wish.The aftermarket kits are actually stronger,as the bolts are drilled parallel to the cylinders,instead of 90 degrees like stock.
     
  7. jlwhite90

    jlwhite90 Junior Member
    from Florida
    Messages: 3

    Sounds like a job best left to the machine shop. Where does one find the 4 bolt kit?
     
  8. wyldman

    wyldman Member
    Messages: 3,265

    Most good performance shops should have them,or your engine shop should be able to both order them,and install them.

    If your not going real high HP,it not really necessary,if you don't want to spend the $$$.Just wanted to let you know it's an option.