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Harley VL degrees of total advance

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  • Harley VL degrees of total advance

    Is the degrees of total advance on a VL motor 35 degrees. I have a set of 1930 flywheels I want to mark TDC and Total Advance. Thanks!

  • #2
    More like 30°. The piston position will NOT be the same as a UL due to difference in stroke and rod lengths. It's about .333" (BTDC, not from the cylinder deck). If the piston to head clearance is too large the engine may knock even at the factory setting.
    If the engine is still apart, this is an excellent time to optimize your quench distance. They are almost always way too loose, and should be tightened to .035" (absolute minimum) to .040" by:
    1. decking the cases
    2. milling the cylinder deck
    3. milling the cylinder flange
    Measure twice, cut once, remember to include compressed thickness of head and base gaskets.
    Important: the piston’s position (height) relative to the top of the cylinder is never, despite frequent comments, “the stroke length ÷ 180, times the number of degrees” in any engine. It’s physically impossible, since a connecting rod of infinite length is required to achieve this. One half (50%) of the stroke doesn’t occur at 90°, ever.
    For reference, based on the 74" V, VL, etc. (not VLH) with 4.00" nominal stroke and 7.6875" rod:
    25° .234"
    26° .253"
    27° .272"
    28° .292"
    29° .312"
    30° .333"
    31° .355"
    32° .377"
    33° .400"
    34° .424"
    35° .448"
    Last edited by kitabel; 09-28-2018, 09:49 PM.
    The Linkert Book

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    • #3
      Shop Dope 260C, the latest I have in a series of specification sheets, calls for 11/32" advance (0.344", 30.5 degrees) for moderate compression engines in solo service, and 5/16" advance (0.3125", 29 degrees) for high compression solo engines with 8.2 heads and all engines in sidecar service. The same sheet says 1930/31 V and VC engines should be timed 1/4" to 5/16" btdc (0.250 - 0.312" or 26-29 degrees advance).

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