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    Machining Heads

    Is removing the valves always required when skimming the head?
    We're out there in here.

    #2
    You can loosen the cam caps enought to relieve the tension off the valve springs. That should give enough clearance for the head to be milled. Any machine shop should now this trick

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      #3
      Depends on what kind of head we're talking about, and how much it needs to be skimmed.

      I wouldn't remove the valves, the machinist can do it if it's necessary.

      '93 Daytonaviolett Touring Design Edition

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        #4
        Just take it to the shop and ask then
        I have had my head resurfaced 2 different times by 2 different shops and one guy made me take all of the valves out (such a pain in the ass) and the other guys machine made it so that the valves didn't get in the way at all

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          #5
          You can skim them with valves in, but they are a pain to clan after - also any carbon in the chamber will score the surface as the cutter crosses it, so I prefer to remove the valves and media blast or tank them prior to cutting.

          A valve job isn't a bad idea, either, since it's already off and coming apart. Heads with any kind of mileage on them will have leaky/pitted exhaust valves.
          john@m20guru.com
          Links:
          Transaction feedback: Here, here and here. Thanks :D

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            #6
            Yeah the head on my nv m50 is warped and the valves stick past the head. I have to take them out so im getting a valve job done and replacing the stem seals It doesn't seem to have been apart maybe the Non vanos valves are a bit different or the seats sit a bit lower?
            We're out there in here.

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              #7
              If the valves are past the deck, you may want to check machining limits. Pretty sure the casting is toast at that point.
              john@m20guru.com
              Links:
              Transaction feedback: Here, here and here. Thanks :D

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                #8
                I agree with John... I machined my head past BMW's spec of 5.500" and the valves aren't anywhere near going past the deck. So you must be waaaay past spec. Could still be usable I guess, just be sure to check clearance before you put the head back on
                -Alex

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                  #9
                  So I've been out of town just got back. I went over and measured it with my machinist.
                  Came out right around 5.515". After cleaning the head in the hot tank the finish on the mating surface was original and the motor has never been apart so it was uncut. The non vanos head must be a bit different. So I'm skimming it over the weekend to get it flat again. Starting at .008 see how I go .01 is the max. Valves all still sealed fine so just a quick lap with grinding compound and throwing it back together with the oem thicker gasket
                  We're out there in here.

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