Piston to valve, piston to head

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by dragster156, Mar 17, 2018.

  1. dragster156

    dragster156 Member

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    What's the minimum piston to valve and or piston to head everyone likes to run.

    Currently the motor has .080" head gasket and has

    .165 exhaust clearance
    .113 intake clearance

    Any thoughts on a ballpark of what going i.e. .010 smaller to a .070 gasket is worth? Or even smaller if can be done?

    Thanks
     
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  2. rpt

    rpt New Member

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    I'm not for sure an expert, but I would think in terms of compression ratio and keep the clearances as a limit to stay safe. So you should measure your static compression ratio first and then think about an higher or thinner gasket.
     
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  3. dragster156

    dragster156 Member

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    I agree.

    The motor was run with an .080 head gasket and with the head on the motor without the gasket nothing hits. So there is at least .080 piston to head.
     
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  4. rb0804

    rb0804 Member

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    I like to be .125 on the intake and exhaust on engines I build for others as there is less chance of there being an issue. The minimum that I would run would be .090 on the exhaust, which will be the one to hit first. As far as the head clearance it depends on if it’s an aluminum or steel rod and how high you plan on turning it. With a BBC engine at 10,500 I’ve had the piston kiss the head with a .083 and a zero deck height. I also tend to like the thicker gaskets they seem to hold up better when things get sketchy. Sucks when something in the drivetrain breaks, the motor zings and you have to put exhaust valves before you can run it again. Lower compression is easier on parts and the tuning window is much larger.
     
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  5. jay70cuda

    jay70cuda Member

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    Are we talking a Hemi or a Chevy? A Hemi with .080 piston to valve on the exhaust will hit after 9000 . Just went thru this 2 weeks ago. And after 9700 the number changes again.
     
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  6. dragster156

    dragster156 Member

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    its a hemi. I will just stick with the .080" gasket, not the end of the world

    most rpm it will see is 84-8600
     
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  7. secondwindracing

    secondwindracing top alcohol

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    Check the valves when they are chasing each other...also your cam timming has alot to do with valve clearances... with a .080 you really knock out a bunch of compression..good luck dave
     
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  8. Dale H.

    Dale H. Member

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    Although I wouldn't advise it, but I have run as little as .050 on the intakes. The exhaust needs around .100 with good springs. The intake isn't as critical as the exhaust being the exhaust valve is chased back up by the piston, and when valve float happens the piston catches up with it. The intake valve on the other hand chases the piston down, so valve float isn't a problem with it.
    -Dale
     
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  9. MaineAlkyFan

    MaineAlkyFan Member

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    Most RPM it should see...

    Just an observation. :)

    Chris Saulnier - Team Tigges
    Mechanic Falls, Maine
     
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