Try to identfy that nailhead engine if its 401 or 425

Discussion in ''Da Nailhead' started by Tony Hadley, Aug 15, 2019.


what cubich inch

  1. 401

    4 vote(s)
  2. 425

    2 vote(s)
Multiple votes are allowed.
  1. Tony Hadley

    Tony Hadley New Member

  2. cobravii

    cobravii Well-Known Member

    I would curious to see the digits stamped in the block right by the temps sensor in the head. That would almost always tell all.
  3. wkillgs

    wkillgs Gold Level Contributor

    The cast in lift hook in the first pic is only on 1966.
    Red mid-sump oil pans usually mean it's a 425, but the '-705' casting number is on 401 blocks.
    As Larry replied, check the ID stamp just in front of the valley pan.
  4. PGSS

    PGSS Well-Known Member

    66 401 with 425 or 66 Skylark GS heads? I can't see any color on the block?
    I did read from Russ Martin they bored the 401 705 blocks to 425 in the day??
    Last edited: Aug 17, 2019
  5. Wildcat GS

    Wildcat GS Wildcat GS

    `66 401 originally delivered in CA
    Tom Mooney

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