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head surfacing, valve removal?

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    head surfacing, valve removal?

    Can you surface the m42 head with the cams and valves in?

    I measured the head being warped .009, so it needs surfaced, but it looks like the intake valves will be in the way regardless. I tried 'closing' the valves all the way and they're still protruding.

    edit:

    maybe the intake valves are bent??
    Last edited by genocide98; 06-18-2012, 11:17 AM.

    #2
    pics?

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      #3
      No pics, head is at machine shop. They didn't look visibly destroyed when I pulled the head, but I got a call this morning saying that the cam(s) would need to be removed because the intake valves are sitting too high to machine over, even when the cams are in 'closed' position.

      I've never worked on an m42, or any 4v/dohc bmw before. I'm not sure if its normal to have to remove the cams to surface the head?

      Additionally, the car ran (albeit poorly) before I pulled the head. I'll be headed down there later to pull the cams out so the head can be pressure tested.
      Last edited by genocide98; 06-18-2012, 11:51 AM.

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        #4
        The valves should really come out, if not to assure your machinist does not make a knuckleheaded mistake, then at least to replace the valve guides. Also if the valves are removed they can be checked for wear/warpage. Just be aware, some shops will want you to put the cams back on to be sure they dont screw up the cam bearings/dodge any liability/avoid actual work.

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          #5
          Originally posted by roguetoaster View Post
          The valves should really come out, if not to assure your machinist does not make a knuckleheaded mistake, then at least to replace the valve guides. Also if the valves are removed they can be checked for wear/warpage. Just be aware, some shops will want you to put the cams back on to be sure they dont screw up the cam bearings/dodge any liability/avoid actual work.
          I have no problem pulling and installing the cams.

          I'm pretty sure the machinist called to ask because they charge for labor, I'm fairly certain the guy wouldn't want to "surface" my valves. He's a good dude and has never done anything silly like that before.

          I'd love to break the head down and inspect it myself but I simply don't have the tools to do so. Hopefully they don't want an arm and a leg to pull the valves =/

          edit:

          Went to talk to the machinist, said he'd need to pull the valves to surface the head because there isn't enough clearance. I went down to check and see what he meant, it looked like that was the case. Is this normal? or maybe the head has already been machined?

          either way $220 to have it pressure checked, disassembled, machined, new stem seals, and reassembled. I don't have a spring compressor so I'd only save $20 to pull the cams myself.
          Last edited by genocide98; 06-18-2012, 03:26 PM.

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            #6
            That's a fair enough price. IIRC on my old cracked head with cams out and valves still in the valves did protrude below the surface, if only on the outer? edges.

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              #7
              the valvetrain should be removed before the head is surfaced. thats the best way

              Turbo M42 Build Thread :Here
              Ig:ryno_pzk
              I like the tuna here.
              Originally posted by lambo
              Buttchug. The official poster child of r3v.

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                #8
                .009" is a Texas mile.

                Removing cams and valves is standard procedure for machine work.
                john@m20guru.com
                Links:
                Transaction feedback: Here, here and here. Thanks :D

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                  #9
                  Originally posted by ForcedFirebird View Post
                  .009" is a Texas mile.

                  Removing cams and valves is standard procedure for machine work.
                  yes.
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                    #10
                    I've never had to remove cams or valves for machine work, but every cylinder head I've had surfaced had the valves recessed enough to have a safe tolerance.

                    The only valves which are in any real danger are the intake valves, from what I measured at the shop.

                    I missed a zero, it should be .0009, or nine one thousandths.

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                      #11
                      that would be ten thousandths... for what its worth the rule of thumb is one thousandths per cylinder.

                      So a 4 cylinder head should have no more that .004 warpage. 6 cyl= .006 ect.

                      also. take the valves out. you probably want to do stem seals anyways while youre in there. do it once do it right
                      Last edited by Dj Buttchug; 06-19-2012, 09:26 PM.

                      Turbo M42 Build Thread :Here
                      Ig:ryno_pzk
                      I like the tuna here.
                      Originally posted by lambo
                      Buttchug. The official poster child of r3v.

                      Comment


                        #12
                        I would if I could, but I can't because I don't have a valve spring compressor. It'd cost more for me to drive down, buy one, pick the head up and pull it apart, drive back, etc, than to have them pull it apart so I'm gonna be lazy and pay to have it done.

                        hopefully its finished tomorrow.

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