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ULH Cylinder queation

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  • ULH Cylinder queation

    Boys I need some guidance here. This has to do with ULH cylinders. Are 74 and 80 cube cylinders the same with one being bored larger or are they different cylinders? I read Bruce’s paragraph on this subject but obviously I’m missing something. Thanks guys, Bob L
    AMCA #3149
    http://www.thegoodoldmotorcyclepartscompany.com

  • #2
    The 74 and 80 13 fin cylinders are the same casting. 80 cylinders were bored to 3 7/16 (vs 3 5/16") and relieved around the valves.

    Jerry

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    • #3
      Thanks Jerry but what do you mean relieved around the valve. I'm not retarted, just slow.
      AMCA #3149
      http://www.thegoodoldmotorcyclepartscompany.com

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      • #4
        Originally posted by Robert Luland View Post
        Thanks Jerry but what do you mean relieved around the valve. I'm not retarted, just slow.
        That means that several thousandths of metal around the valve is ground away to provide a better flow towards the bore.
        Be sure to visit;
        http://www.vintageamericanmotorcycles.com/main.php
        Be sure to register at the site so you can see large images.
        Also be sure to visit http://www.caimag.com/forum/

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        • #5
          The 13 fin cylinders have 120-37 and 120-371 cast in the front/rear base flanges. They will be used on the 1937 Big Twin flatheads and the 1938-41 ULH models. The 11 fin cylinders have 120-38 and 120-381 cast in the front/rear base flanges, and were used on the 1938-48 74 cubic inch flatheads.
          Last edited by Steve Slocombe; 03-30-2012, 04:21 AM.

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          • #6
            Bob Cylinder on the left is ULH and the cylinder on the right is UL - both 13 fin.







            Jerry

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