Results 1 to 10 of 10

Thread: cylinder boring

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Join Date
    Dec 2009
    Location
    Upstate NY
    Posts
    113

    Default cylinder boring

    Want to put new pistons in my panhead. Made a ring fixture to mount in a 4 jaw chuck. OD and ID run true, has 4 holes in the face to mount the cylinder. Trued the ID in the lathe and made the hole a slip-fit for the sleeve end for the jug. Faced the fixture so the cylinder base would run true to the bore. I mounted the first cylinder and indicated near the top of the bore, and it runs out .008". Ran the indicator down the bore and it's good within .002" in 3 or 4 spots. The bore is stock (3.4385"). Is this something anyone has seen? I thought the bore would run truer than that provided the face of the fixture was true to the axis of the lathe.

  2. #2
    Join Date
    May 2009
    Posts
    138

    Default

    I made a similar fixture that bolts to the top of the cylinder. I find that the base flange is seldom flat. After boring, I true the flange.

  3. #3
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
    Posts
    4,276

    Default

    Ideally, Folks,...

    Your fixture should stress the cylinder as if it were installed upon the cases with heads.

    HDs distort from fastener stress at their long spigots, more and more dramatically as the bore increases.

    By the time an HD cylinder is .060" over stock, stress plates for the final hone-fitting are more than prudent.

    ....Cotten
    Attached Images Attached Images
    Last edited by T. Cotten; 09-03-2019 at 11:32 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  4. #4
    Join Date
    Dec 2009
    Location
    Upstate NY
    Posts
    113

    Default

    OK, thanks for the tips. Just a couple questions. First, for Cotten, what's that flange piece with the screws in it for? And for Larry, when you true up the flange, do you fixture it in the lathe by bolting through the head bolt holes to the surface on the jug that mates with the head, or do you make some kind of expansion arbor to fit the fresh bore on the cylinders?

  5. #5
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
    Posts
    4,276

    Default

    That's lagged to the bench, Omar!

    The "torque plates" have notches for the bolts in the fixture, so the assembly can be held firmly for a convenient and accurate torque.

    The idea is that the cylinder should go back to 'round' when installed in the motor, at the same torque spec.

    Once again, although always beneficial, it is at larger over-bores that this technique becomes critical.
    Horror stories of fragged cylinders or severe overheating could have been avoided.

    ....Cotten
    PS: Carbs distort too.
    Attached Images Attached Images
    Last edited by T. Cotten; 09-03-2019 at 11:28 AM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  6. #6
    Join Date
    May 2009
    Posts
    138

    Default

    Bolts to head and can act as a torque plate.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •