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Thread: Need advice, 61" Knuck cylinders on a 74"

  1. #1

    Default Need advice, 61" Knuck cylinders on a 74"

    I have a very nice set of late 5 fin 61" Knucklehead cylinders that have been bored out to 74" standard bore.
    What are the pros and cons of using them on my 47 74" bottom end?
    Obviously the compression bumps because they are about a 1/16"?? shorter.
    Does using low or medium compression pistons bring it back down to the standard high compression ratio?

    I have some +0.060" 74" 5 fin cylinders that I could use but these 61" have no fin damage at all, have correct and matching date codes for my engine VIN.

    What's the value of 61" cylinders compared to 74"?
    These could always be sleeved and brought back to being VERY NICE 61" cylinders.

    Thanks in advance for your input.
    Mark Masa

  2. #2


    The height difference is .125" (5.530" vs. 5.405"), which may cause piston to valve or piston to head contact.

  3. #3
    Join Date
    Jun 2001
    Central Illinois, USA



    Were the over-bored cylinders fitted for pistons while stress-plated?

    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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