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Thread: 66V head

  1. #1

    66V head

    I am rebuilding my GPR, and was considering having the head milled to bump up compression a little. I donít mind running 92-93 octane, but am NOT running race gas. E85 is a possibility as well because of the extra octane, but the extra E on a watercraft makes me nervous. How much compression will the 66V handle on stock timing and 92 pump gas? How much would have to be milled off the stock head to bring it to that?

  2. #2

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    Call Newmiller machine and have a talk. He will ask you what type of riding you do, what fuel is available and what altitude you’re at. Then make an educated suggestion for your ski.


  3. #3
    Thanks! Iíll get in touch with him!

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  5. #4
    jeffg426690's Avatar
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    You can mill about 20thou off a stock 66v head without doing anything w yhe domes. Will give you 135-140-ish, 92 or 93 works just fine w it.

  6. #5
    Jeff, thats perfect. Thank you. Donít wanna go crazy, just want to make use of a bit more octane to get a little more ďoomphĒ so to speak.

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  8. #6
    Myself's Avatar
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    I usually just drill the rivets on the metal head gasket and remove one layer. I've done it on the 1200r and the 800r.

  9. #7
    Quote Originally Posted by Myself View Post
    I usually just drill the rivets on the metal head gasket and remove one layer. I've done it on the 1200r and the 800r.
    How did it work out? How much psi did you gain? Any noticeable difference in performance?

  10. #8
    Myself's Avatar
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    There is a slight difference overall. Most recently a customer had XLT1200 twins. A his & hers combo. On his I removed the extra intake baffling, and took one layer out of the head gasket. His is slightly quicker out of the hole and more punchy feeling throughout the midrange. It bumps compression up about 10psi.

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