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  1. #1
    It got WIFI and touchscreen ! PWCGUY's Avatar
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    Decking the Head Increase compression ?

    Just ordered a larger SC and plan to go through the motor this winter. One cylinder is a little low on compression ( 125 psig ) so I will probably hone and put new rings in this cylinder. Also plan to go through the head lapping all valves and Riva valve train upgrade. Based on posts I've read the head gasket on these motors is a weak link when runing higher boost and RPM's so I want to minimize the chance of blown head gasket next season which leads me to the question.

    If I have the head decked will it increase compression ? Do you use a thicker head gasket ( if it exists ) ? I definitly do not want to increase compression on this motor so any feedback would be appreciated. Also where can I get the copper spray to coat the head gasket ?


  2. #2
    yes, depending on how much it`s cut. but nontheless, yes.
    also if you did that, you`d have to check cam timing and adjust as needed.

    copper spray can be found at most auto part stores and speed shops.

  3. #3

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    I believe that RR makes a thicker head gasket. Contact PPG for help.

  4. #4

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    Pale Rider is correct. Any milling of the head will increase compression. After milling--obtain and piece of clear plastic
    (at least one quarter inch thick) that will cover the milled head surface. Then after you have finished any and all work on the valves and they are installed and seated--turn the head upside down--fill the combustion chanbers with baby oil. Then take your clear plastic and lay it over the combuation chambers and make sure ther are no air pockets just under the plastic. Remove the plastic--the measure how many CCs of fluid are in each chamber. Then find in the service manual how many CCs are on a stock uncut head. This way you can calculate what your new compression ratio will be. If you only cut a minamal about you would not have raised compression to a danger level. Also as you increase boost you also increase compression ratio.

  5. #5
    It got WIFI and touchscreen ! PWCGUY's Avatar
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    Thanks for the feedback so far ! Based on this I need to rethink strategy. Is there an easy way to check flatness of the heads mating surface ? Maybe I can avoid decking it.

  6. #6
    Quote Originally Posted by PWCGUY View Post
    Thanks for the feedback so far ! Based on this I need to rethink strategy. Is there an easy way to check flatness of the heads mating surface ? Maybe I can avoid decking it.
    if you have a perfect squared straight edge, go across the center length wise and corner to corner, use a feeler gauger under the straight edge and measure any gaps, then check with the service manual for specs...

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