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85 350 Engine in 86 K5

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by johnny reb, Dec 5, 2000.

  1. johnny reb

    johnny reb 1/2 ton status

    Mar 6, 2000
    Likes Received:
    Pittsburgh, PA
    Just talked to Scoggins Dickey about a new GM Goodwrench 350 for my 86 K5 (currently has a 305). He said most people get the 1985 crate engine and change the flywheel. He said the flywheel was about $50. What is involved in this modification?
  2. HarryH3

    HarryH3 1 ton status Author

    May 31, 2000
    Likes Received:
    Georgetown, TX
    Your 1986 engine should have a one-piece rear main seal, which also means that it has a different crankshaft than the pre-86 engine. Your 1986 flywheel won't bolt to the 1985 crankshaft (with it's two piece main seal) so you'll have to purchase the flywheel that fits the 1985 engine. It will bolt right to the new engine.

    I think 1986 was also the first year for the factory roller cam, so you'll lose that as well. The 1985 engine will have a flat tappet cam.

    You may also have to do a little drilling or grinding on the intake manifold so it will bolt to the old heads. The angle of two of the bolts changed in either 86 or 87, I can't remember which. If yours has TBI, then the bolt angle is slightly different than the '85 heads.

    <font color=black>HarryH3 - '75 K5</font color=black>

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