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Thread: 3800 Series II NA. Head Milling

  1. #1

    3800 Series II NA. Head Milling

    Ok, so I've seen a lot of numbers thrown around, but I can't find the right number. Does anybody know what the Max i can take off of these heads is without touching anything else? P&P heads with 140# springs, stock length push rods and stock length valves.

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    Full Throttle SlasherVRGR's Avatar
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    Quote Originally Posted by Brian_mf View Post
    Ok, so I've seen a lot of numbers thrown around, but I can't find the right number. Does anybody know what the Max i can take off of these heads is without touching anything else? P&P heads with 140# springs, stock length push rods and stock length valves.
    That would depend alot on the cam, duration plays more of a factor than lift. Best way would be to do some measurements and go from there.

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    Full Throttle SlasherVRGR's Avatar
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    Also on a side note, any time you mill heads, change heads, or change rockers you should measure pushrods to be sure they're the right length.

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    98 Maro
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    Much nicer, better, cleaner, and most importantly faster than the old one

  6. #5
    Thank you for the advice. I suppose ill be researching/asking more questions in the near future as this is my first time doing something like this. I really appreciate it.

  7. #6
    For what it's worth, my heads are milled 0.050" with 0.045" head gaskets and I'm running an Abbot Racing Cam. My LIM is milled 0.030" on the bottom and 0.22" on the sides.

    My pushrods are at least a couple sizes shorter but I can't remember their length.

    I've read that anything past a 0.040" lower head deck height for milling and thinner head gasket combined should have the LIM milled.

    Stock lifters can only compensate for a 0.015-0.20" increase in preload. (I think this more or less answers your original question)

    Keep in mind aftermarket cams usually have a smaller base circle. So, it's not as simple as subtracting the shorter gasket/milled distance for pushrod length.

    And finally, if you P&P the heads and have a valve job done, the valve will sit slightly taller in the head and load the lifter more. That's assuming they don't shave the top of the valve to compensate.
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    ┬─┬ ノ( ゜-゜ノ) triple_l82's Avatar
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    the max that has ever been milled was .020 flat, .080 milled, and then another .020 or .035 flat. whatever the final flat was done ended up being a total of .120-130 milled off the heads and thats when one cracked. You can safely mill flat .1 on these heads, several have been done to .060 flat. For best results go angle milled at .60 or .080 as it will roll the valve angle and makes the most difference. After milling though have the intake milled to match and fit, after that happens the heads and intake will be a matched set and can not be mixed with others.
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