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731 Head- No Steam Holes?

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    731 Head- No Steam Holes?

    M20 experts-

    I was dropping off my 731 head at the machine shop when I realized that the 731 head has no steam holes.

    There was obvious corrosion where the steam holes are supposed to go. In small block 400 heads they added these steam holes, and if blocked off caused pretty bad air pockets that would create heat marks in the bores for whatever reason.

    Am I fine to run the 731 head and block those steam holes off on the block? I'm worried about air pockets forming there as well as corrosion build up.

    I checked other 731 head photos online, and none of them had them.

    Untitled by Bobbie Morrone, on Flickr
    Untitled by Bobbie Morrone, on Flickr
    1989 Zinnoberrot M3 Build Thread
    1990 Brilliantrot 325iS Build Thread

    #2
    its been done before, i say you are GTG
    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

    new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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      #3
      Cool, thanks. The 731 needed welding around corroded coolant jackets and had a junk surface finish so if I needed to change something re: steam ports, now would be the time.

      Cometic states anything finer than 50 RA is acceptable. The surface on there was way higher. The machinist said "whoever did this needs a new cutter" lol.
      Last edited by AWDBOB; 09-20-2019, 08:57 AM.
      1989 Zinnoberrot M3 Build Thread
      1990 Brilliantrot 325iS Build Thread

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        #4
        Im glad you resolved that so I dont have to search for pics of my 731 :)

        Im curious as to why you are using a cometic ?
        Deck Lid and soft top Shocks on hand

        Seat shocks on hand for immediate shipment
        https://www.r3vlimited.com/board/sho...86#post4944786
        Alice the Time Capsule
        http://www.r3vlimited.com/board/showthread.php?t=360504
        87 Zinno Cabrio barn find 98k and still smells like a barn. Build thread http://www.r3vlimited.com/board/show...20#post3455220

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          #5
          Originally posted by jeffnhiscars View Post
          Im glad you resolved that so I dont have to search for pics of my 731 :)

          Im curious as to why you are using a cometic ?
          I was about to PM you!

          I’m using cometic because I’m going 86mm bore.
          1989 Zinnoberrot M3 Build Thread
          1990 Brilliantrot 325iS Build Thread

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