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Technical Valve stem size on ‘62 Mercury

Discussion in 'The Hokey Ass Message Board' started by 67drake, Apr 27, 2020.

  1. 67drake
    Joined: Aug 8, 2008
    Posts: 207

    67drake
    Member
    from Avoca WI

    Waiting to get my block, heads and crankshaft back from the machine shop. I called on the progress today and was told the only hold up was that they were assuming the valve stems were normal 11/32” diameter, and mine are 5/16”. I guess they haven’t run into this before. This is my first Ford rebuild, but I had researched the build before I started it, and had never heard of the valve stem size difference.
    Are my ‘62 260 V8 heads that much of a oddball?
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 51,178

    squirrel
    Member

    They didn't measure them? Hmmm.....
     
  3. 67drake
    Joined: Aug 8, 2008
    Posts: 207

    67drake
    Member
    from Avoca WI

    I guess not.
    They said the valves that came with the kit that they ordered had the 11/32”. It just seemed a little odd that my original heads would be different than a run of the mill 289,302. It caught them by surprise. I just figured someone here might have run into this before. I kind of suspect they were making an excuse because they’re behind schedule with the completion
     
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 51,178

    squirrel
    Member

    The early engines had quite a few differences. But it's a good excuse, I supposed.
     

  5. Beanscoot
    Joined: May 14, 2008
    Posts: 2,370

    Beanscoot
    Member

    260 heads also had smaller combustion chambers than 289s.
    Early 260s had lighter connecting rods and a differently balanced crankshaft than the later 260.

    All 1962 are early, all 1964 are late. But I don't recall when the changeover was.
     
  6. 67drake
    Joined: Aug 8, 2008
    Posts: 207

    67drake
    Member
    from Avoca WI

    Good info.
    Thanks guys!
     
  7. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,462

    seb fontana
    Member
    from ct

    All the 260's I had were 5/16 stem, all my Ford books say 5/16 [.310]. 11/32 didn't start till 289 cube.
     
    squirrel likes this.
  8. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,641

    sunbeam
    Member

    seb is right 221 and 260 had 5/16 valve stems.
     
  9. Arominus
    Joined: Feb 2, 2011
    Posts: 394

    Arominus
    Member

    If you have guides that will work, run the smaller stems, that’s a little bit of airflow and less weight to move.
     
  10. Beanscoot
    Joined: May 14, 2008
    Posts: 2,370

    Beanscoot
    Member

    1964 260 engines had 11/32" nominal valve stems (actual 0.3410"), same part number as the regular 289 engines:

    Ford MPC valves 011.JPG

    Ford MPC valves 013.JPG
     

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