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DIY e30 M20 valve spring compressing technique

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    DIY e30 M20 valve spring compressing technique

    Hi All, I have searched and seen many different methods and tools to compress valve springs, but not a method like this. Perhaps this will help others rebuilding their m20 heads.

    Since I was only doing one head, I thought I could get by with the Harbor Freight "universal valve spring compressor". But (surprise, surprise), it didn't work well. Normally I would spring (pun intended) for a proper tool, but thought "this is not that complicated, the tolerances are not tight, and the forces are not large, so there must be a better way".

    The problem with the HB tool is that it only grabs (and frequently falls off) the larger outside spring, but doesn't compress the inner spring. But the adapter on the tool is useful. So here's what I did...

    Tools required:
    6" C clamp
    Harbor Freight Universal Valve Spring Compressor
    Magnet tool

    Here's the Harbor Freight tool:
    Click image for larger version

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    I needed the adapter, so I removed the c-clip:
    Click image for larger version

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    then I used pliers to adjust the adapter...
    Click image for larger version

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    ...to fit the spring retainers with clearance for the keepers:
    Click image for larger version

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    Place a towel around the top, side, and bottom of the head where you'll be working:
    Click image for larger version

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    continued on the next post as I've reached my maximum photo upload
    Last edited by mybimr; 01-13-2016, 03:28 PM.
    current fleet: '89 325is; '91 325ic; '88 325is; '91 325i

    #2
    ...continued from above

    ...continued from previous post

    Place the adjusted adapter on the valve spring retainer:
    Click image for larger version

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    the next step is to take your 6" c-clamp and place the fixed end over the valve (on the bottom), making sure the towel is between the tool and the head in all places:
    Click image for larger version

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    hold the clamp assembly in-line with valve stem/spring assembly as you compress the spring. the adapter will stay on top of the spring due to it's retaining tabs:
    Click image for larger version

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    continue until the retainer clears the keepers:
    Click image for larger version

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    Use a magnet tool to remove the keepers:
    Click image for larger version

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    I hope this helps others. It worked really well for me. This may work on other heads, but the M20 is 175mm (just over 6" tall) with interference valves, so the valves are not so recessed into the head that the flat end of the clamp can't reach them. The towel is important since it's very easy to scratch the aluminum head.

    PS - if you don't have the HB tool, you might be able to do this with an O2 socket and a larger c-clamp. I checked and the socket fits, and has a nice slot for grabbing the keepers, but it's too tall for a 6" clamp.

    Cheers,

    Gregg
    Attached Files
    Last edited by mybimr; 01-13-2016, 03:23 PM.
    current fleet: '89 325is; '91 325ic; '88 325is; '91 325i

    Comment


      #3
      And here's what you end up with:

      Click image for larger version

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      I was surprised to find a broken outer spring on the #1 exhaust valve. I have no idea how long I had driven with that situation! I don't recall ever noticing anything out of whack...I guess it demonstrates that the engine will run with only the inner spring lol!:D

      Click image for larger version

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      Attached Files
      current fleet: '89 325is; '91 325ic; '88 325is; '91 325i

      Comment


        #4
        Notable ingenuity. Option B is go to Advance and get their free rental C compressor :)
        Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com

        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

        Comment


          #5
          Ahhh, I didn't check there. I looked at my local autozone, and they only had one similar to the harbor freight style.

          Sent from my SM-N900V using Tapatalk
          current fleet: '89 325is; '91 325ic; '88 325is; '91 325i

          Comment


            #6
            Autozone hasn't had the C type here.
            Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com

            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

            Comment


              #7
              the forces are not large
              I had an old sliding- bar style woodworking clamp I'd used for years-
              worked great, never had a problem.

              Until a stuck retainer caused me to overtorque it, it slipped off at the wrong time, and the
              spring went through a florescent light. Made an unholy mess.

              I spent the $75 for a good one.

              STILL had to make something to get the M42 apart...

              Watch your eyeballs out there!

              t
              now, sometimes I just mess with people. It's more entertaining that way. george graves

              Comment


                #8
                If I had to do this regularly, I would have tack welded or epoxied the adapter to the clamp. With the tangs on the adapter, it would be very difficult to slip off. But I concur, be safe everyone! It's like playing with a red Ryder bb gun...and you know what your mom always told you!

                Sent from my SM-N900V using Tapatalk
                current fleet: '89 325is; '91 325ic; '88 325is; '91 325i

                Comment


                  #9
                  I bought an overhead valve spring compressor tool at sears for like $35. works perfectly, no DIY required. :p
                  Build thread

                  Bimmerlabs

                  Comment


                    #10
                    C-clamp and spark plug socket with a window gently put in it with an angle grinder, worked great . . .
                    just another option
                    1991 325i - "Scambles" The Daily Driven lightly modded.
                    1988 Mazda RX-7 TII "Mako" The Free Dorito
                    bacon by Jared Laabs, on Flickr

                    Comment


                      #11
                      I bought an overhead valve spring compressor tool at sears
                      ...but where's the fun (and stitches) in that????

                      t
                      now, sometimes I just mess with people. It's more entertaining that way. george graves

                      Comment


                        #12
                        the fun was fully disassembling the head in 15 minutes, lol.

                        actually, I'm going to end up using it again on my N52, and I haven't touched it in like 10 years.
                        Build thread

                        Bimmerlabs

                        Comment


                          #13
                          After seeing this, I'm super stoked to pull apart a head. I've got an m30b35 that sounds like it could use some head work, so that'll be a great chance to try stripping it down.
                          sigpic
                          1987 - 325i Convertible Delphin Auto [SOLD], 325i Convertible Delphin Manual [SOLD]
                          1989 - 325i Convertible Bronzit m30b35 swapped [SCRAPPED], 325i Sedan Alpine Auto[DD]
                          1991 - 325i Coupe Laguna Manual [Project], 535i Sedan Alpine [SCRAPPED]

                          Comment


                            #14
                            Socket and hammer FTW. 😎

                            Sent from my E6653 using Tapatalk

                            Comment


                              #15
                              I found that the compressor I had for the M10/20/30 didn't work on the M42.
                              Didn't go deep enough, so I ended up making something very like Awaken's
                              socket, except with the old woodworking c- clamp.

                              t
                              now, sometimes I just mess with people. It's more entertaining that way. george graves

                              Comment

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