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Cylinder Head Evaluation + Decisions on Rebuild

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    Cylinder Head Evaluation + Decisions on Rebuild

    Hey there, I have been following this site for a long time during my last E30 restoration/rebuild. First time posting here, I hope this is in the right spot and everything. But anyway, I'd like to feel out some opinions on the next step of my engine restoration.

    On my 1988 325i, I had a failed/cracked head I discovered when I pulled the head. I recently acquired a cylinder head. The head was only $225 but has a broken rocker arm. The guy I bought it from suspected a hydraulics failure of some nature but I also am anticipating that this could have been a high rev'd out head? I am anticipating the camshaft lobes may be quite worn so I've already sourced a new camshaft. The head was clearly recently machined and still is shiny and clean on pretty much all the surfaces. It also has great-looking newly replaced studs. I am trying to reduce costs that are unnecessary (the last restoration I spent all of a $5k budget really quickly on unnecessary parts so trying to learn from those errors). So here are a few questions:

    1. Can I reasonably avoid another trip to the machine shop? With it having been machined recently, it looks in great shape overall. The valves all seal properly and are not bent. No cracks on a macroscopic level noted. I don't want to skip this important step of having a machinist evaluate, but I do feel having a valve job done when everything seals well and is in good shape might be futile.

    2. Thoughts on using a used rocker arm to replace? I have a cracked head with good rockers that I've thought of using for spare parts. But I'm also considering replacing all rockers and the rocker shaft with new components.

    Thanks and sorry for the lengthy post. I would love to hear what others would do in this situation. I plan to strip the head the weekend and do lots of measuring of the components. I'm hoping the valve springs are within spec, they're pricey.

    #2
    Noone can realistically answer the question 1 except for a machinist who has done a disassembly, inspection and report.

    Every time I've done a head on a car ive dropped it off at the machine shop and got them to do a disassembly, inspection and report. and most of the time they have come back with a few things that need doing and you just pay the money and you put the now known good head on and now for the life of that head you now know that on X date and X km it was in perfect condition.

    Other people do things differently but for me, you drop it off and let the pros do their thing. if it looks as good as you say it is then you might not be up for any machining costs and it will be a cheap trip. Unless you have a way to check it you'll never know that your valve stem seals are leaking. My last m20 head "ran fine" but upon inspection all the exhaust valve stem seals were stuffed.

    question 2, good question, no idea.
    Last edited by e30davie; 01-13-2022, 05:44 PM.

    Comment


      #3
      Rockers break from high RPM, especially if they're the Febi replacement. Check to see if that was the case on the head.. As for the hydraulics, the rockers are mechanical and just have oil passing through the rocker shaft. Idk what that guy was talking about.


      1. I would personally send it to a machine shop to pressure test the head to insure that there are no cracks. Was it sent to be machined under your possession?

      They're gonna have to disassemble the head to really take a good look at it, so I'd spend the money for to know for sure and just have them assemble the head for you after they look over it. Doesn't mean you need to do a valve job, but if you did, then you'd just know for sure that it was done right and correctly

      2. If you have original BMW rockers, and they're not oddly worn, I would use those with confidence. Otherwise, if you're spending the money to do it right, I would go with HD rockers. Those are the only new ones I'd put on a head. The Febi ones are not good. I would not be surprised if the broken one was a Febi.

      Replacement rocker shafts are also not the best. I would just go with the rocker shafts, rockers and cam from your old head. I don't see why you'd want to source another one if the head casting just cracked.

      If you do decide to replace the cam, make sure you see the correct stamping on it. SETA cams and i cams can be easily mixed up. Also, people will sell SETA heads (885) as and 'i' head, when it's really not.

      Different cam and single valve springs. Make sure you see the double valve spring or the correct marking on the cam for the i cam.

      A SETA cam will have an "M" stamp right at the cam journal on the cylinder one side. I can't remember for sure what the i head is stamped. I'm thinking a P or an L


      So, just keep that in mind. Hope that helps
      Originally posted by wholepailofwater
      Q
      :devil:


      WTB: Dove Grey e36 Front Door Panels (2 door)

      Comment


        #4
        get it inspected by a reputable shop, if there is nothing wrong then there are no parts that will be replaced unnecessarily. You aren't wasting money, you are alleviating the risk that whoever did the previous work was either incompetent or did a half a job based on the customer at the times request to do the minimum amount of work. If the head has been on a running engine then there is a risk it was damaged (cracked) due to an overheat so a pressure check will diagnose that. Some of this depends how long you wan the engine to last or be useful before it gets onsold to someone else
        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

        Comment


          #5
          Yup, the word's 'risk'- the cost risk of reassembling the head yourself with cam and new rockers is pretty low- a set of gaskets, and you're done.

          I tend to do this when I'm cash poor. I do also, however, have a straightedge and measuring tools, and measure the head to make sure it's not thin or warped.
          I also install the cam, by itself. If it slides in, I'm confident. If it pushes in with some pressure, I'm less confident. If it's hard to get it to go, I tend to rethink.

          However, when I've got money for the project, it goes to a machinist friend, and always comes back either free, in a red bag, to go in the 'cut it apart for fun' bin,
          or it costs me $500 or so to get it back from him- and then I get to add more money for the parts he kept for himself 'because they were bad'.

          So yeah, if you don't mind the time risk, you could try running it. I once even re- used a head gasket on a 'there's no way this thing is good' engine,
          and then got to change it 3 months later out of paranoia when the darned thing WAS, in fact, still ok.
          I was a lot younger then.

          t
          it's your money, your time, and sometimes both.
          now, sometimes I just mess with people. It's more entertaining that way. george graves

          Comment


            #6
            R3V is getting soft, not one poster simply stated "OP, you need to get your head checked."

            Comment


              #7
              Originally posted by roguetoaster View Post
              R3V is getting soft, not one poster simply stated "OP, you need to get your head checked."
              Us - R3v is so dead

              *new member joins*

              Also us - Hey noob, show us your GF tiddies
              Originally posted by wholepailofwater
              Q
              :devil:


              WTB: Dove Grey e36 Front Door Panels (2 door)

              Comment


                #8
                Get a 30X jewelers lens and look it over closely. No use paying a machine shop for finding a problem you can see for yourself.

                Comment


                  #9
                  Originally posted by packratbimmer View Post
                  Get a 30X jewelers lens and look it over closely. No use paying a machine shop for finding a problem you can see for yourself.
                  This is advice that leads to regret.
                  Originally posted by wholepailofwater
                  Q
                  :devil:


                  WTB: Dove Grey e36 Front Door Panels (2 door)

                  Comment


                    #10
                    Just to clarify, I'm saying that a 30X lens will save you a trip to the machine shop if you find a crack or problem.

                    Comment


                      #11
                      Yup, we're getting old. and soft. The gf's left.

                      just sitting in front of an unlit stove with the dog.

                      shit, the dog left.

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

                      Comment

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