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M42 valve seat specs

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    M42 valve seat specs

    Hi to all of you! :) My name's Matteo.
    I kindly need some information about M42 valve seat job.

    My head suffered from crack in cylinder 2, from water passage to exhaust valve seat.
    Also in cylinder 3 there's a crack between exhaust valves.

    I have to cut it and weld. Then remake valve seat.



    Some information:
    Valve seat width

    Intake mm 1.65 ± 0.25

    Exhaust mm 2.0 ± 0.25


    Ø valve seat

    Intake, outer Ø mm 32.4

    Exhaust, outer Ø mm 30.1


    Ø valve diameter
    Intake 33 mm

    Exhaust 30.5 mm



    I can proceed with valve cutters, but I need confirm. Which diameter of valve cutter should I use for intake and exhaust valve seat? Angle for both is 45 deg.
    Maybe addressing this question to those who already have done this.

    Many thanks.
    Teo

    #2
    Just get good used head, instead. "Passion is timeless"
    '91 318i (Alpine) - daily
    '88 325ix (Zinno) - drive here and there!

    Comment


      #3
      Repairing the cracked head is not likely to give a good long term solution since the cracks go all the way through, and a weld will penetrate only part of the depth. As fresh_td said, finding a good used head will provide much better results. These engines do not like to overheat, which is probably the cause in most cases, but I also suspect that maybe there were some issues with quality control during production (maybe a defect in one of the molds) since some heads seem to crack very easily, and some seem to have no problems ever.

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