xu9j4 head (maximium) skim with valves in?
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  1. #1
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    Default xu9j4 head (maximium) skim with valves in?

    Anyone know the maximum amount an xu9j4 head can be skimmed before removing valves?

    I requested my head rebuilder to skim 0.5mm off but after measuring it today (131.8mm height) it looks like only a minimal amount was removed.

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    Over phone he sounded as though he was going to place head in machine as is for the re-face... I know 0.5mm is a no-no but would be great to know what the limit is before i go to the shop tomorrow morning.
    89 Pug 405 Mi16
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  2. #2
    1000+ Posts PeterT's Avatar
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    When the cutter hits the valve seats.

    Why would you skim it with the valves in?
    Last edited by PeterT; 5th December 2016 at 09:34 PM.

    '92 205 Mi16
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  3. #3
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    less work for them I guess... as I would be happy with at the minimum a 0.3mm skim, due to also increasing comp with a 0.7mm cometic head gasket.

    Even though they should certainly absorb the labour if they have to remove valves again. Which I will insist on if that is the case.
    89 Pug 405 Mi16
    Possibly for sale....

    WRECKING/ Parts Car:
    Blue 89 405 Mi16

  4. #4
    Fellow Frogger! Bluey's Avatar
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    Why would you skim a 16V cylinder head more than the minimum amount needed to make the face straight?

    0.5mm skim would be lucky to gain 0.1 compression points while reducing the useable life of the head because if it warps from overheating or you go to service it again there wont be enough meat to skim it straight.

    Skimming heads to increase compression is a pushrod V8 thing. On a pent-roof twin cam it's stupid and on a 8V cambelt/timing chain engine it messes up the timing so why make things difficult?

  5. #5
    1000+ Posts PeterT's Avatar
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    You can safely take up to 2.0mm off an 8V head but you need to reset the cam timing.

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