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  1. #1
    fixer's Avatar
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    What is the maximum safe compression cutoff for running pump gasoline?

    Bolted the OP head on my 750 project today & went with the .015 copper gaskets & ran a compression test & got 145's (+\-) cold.

    I would imagine I'll be over 150 broken in & warmed up. Can I still run pump gas?


  2. #2

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    theres alot more to it then compression with when you run the triple pipes you have alot more things that add up to you running pump gas . i would start out with 100 oct to be safe and go from there. 150 lb is safe for a regular motor and pipe but with the triples i would say better safe then sorry

    you should check your squish too

  3. #3
    fixer's Avatar
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    How can I check the squish on this Ocean Pro head ? It's got that swirl pattern in the dome.

  4. #4

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    Quote Originally Posted by fixer View Post
    How can I check the squish on this Ocean Pro head ? It's got that swirl pattern in the dome.
    HMMM maybe Xlint can chime in

  5. #5
    Connecticut CrazyA's Avatar
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    Only the dome is swirled, not the outer squish area, which is what will be measured.

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Right ^^^^

    You're checking the clearance in the quench area. (outer area where the piston comes closest to the head)

    CrazyA posted a how to check squish in the tech section. Check it out.


    If memory serves me correct, Ken at OP said the heads should have 43 thousandths clearance at the squish. (quench)

    But Randy at Watcon feels that anything less than 55 and the guys at Sharp's say 60 thou is too little and invites detonation.

    Please feel free to call ken and discuss it with him. He's a really nice guy and should help you out

  7. #7
    fixer's Avatar
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    I get 52. So if I want to run pump gas I'm going to have to step down to the .030 head gaskets, correct?

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    You're right around the cut off for 92 octane now.

    If you install the 30 thou gaskets, you should be fine.

  9. #9
    fixer's Avatar
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    Can I run 92 set up like this? Can I run octane booster?

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by fixer View Post
    ... Can I run octane booster?
    Be careful with that stuff. It doesn't work like people think it does.

    If you need more octane, either run the more expensive fuel or reduce the compression enough to be safe on pump gas. Reducing compression is the safer and less expensive option.

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