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M42 Head Gasket Blown, Project Thread

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    #46
    the other thing is with a say 1.74mm gasket the pistons need to sit above deck by 0.74mm to have a 1.00mm squish. it doesnt look the pistons are set up that way probably because the gasket overhang prevents that, which another bonus of a MLS. the CR will go up but its often said the CR increase is offset by the superior mixture motion so knock resistance is actually better.
    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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      #47
      For some reason I want to see your last sentence written as a haiku.

      CR will go up
      offset by mixture motion
      knock resistance high

      Comment


        #48
        Originally posted by bmwman91 View Post
        For some reason I want to see your last sentence written as a haiku.

        CR will go up
        offset by mixture motion
        knock resistance high
        Make this a topic
        Conversation in haiku
        No other garbage

        Comment


          #49
          not visit Metric
          weather bad squid is busy
          go later in year

          There was a period of time when Bimmerforums' off-topic was doing it. The good old days, when we were all a lot younger and dumber.

          Also, it looks like I am NOT going out to MM next week. Sssquid is pretty busy, flight options with my miles are not optimal and it'll probably be 2x the driving time versus later in the year. So instead I sent MM an email with a list of specific questions from topics in this thread, and I'll plan to hit up KC a bit later in the year to visit Sssquid and MM. They could hold off on assembling my engine until I am ready to get out there, but neither they nor I want that since it's a pain in their ass and I want the car running again.
          Last edited by bmwman91; 01-24-2020, 09:12 AM.

          Comment


            #50
            Quick update...

            MM is going to have my engine all finished up by the end of the week. It turned out that my pistons and rods were totally fine, and while they are not the most-current design that MM uses, they are actually a newer design that they had just started using at the time. They had assumed that I was using some older stuff than I was, so they cleaned all of it up and installed new rings of the design that they currently use. The pistons and rods are not quite as light as the current stuff, but they are close enough to not be worth replacing and the crown profile / valve reliefs are current.

            My previous block was not reused. I had run it pretty hard and it was out of round by around 0.001", although the failing HG may not have helped and the break in oil I had used initially could have caused excessive wear. Re-honing would have led to me either needing new custom pistons for the slightly larger bore, or burning more oil if the pistons were reused. So MM machined up a spare block for me to hit the desired clearances (0.0029 - 0.0032 all around), and add all the stuff my previous one had (windage tray, oiling mods, etc), plus changing over to use ARP head bolts with a larger shank and finer thread pitch. They have found that they get the most consistent bolt torque with these, versus the stock & Victor Reinz ones that were used on the previous engine (unknown if blown HG was related).

            The head was fully pressure tested. There was no bubbling at all that could be found anywhere, which is a relief. Valve seats got replaced and have a new multi-angle grind that MM had come up with since the first engine was made. They believe that it increases flow slightly, so we'll see I guess. It needed a few thousands shaved off to get the deck perfectly flat. The inter-cylinder sections, particularly between #2 & #3, had a little galling from the shredded metal gasket, which has been surfaced out. Everything else looked good inside, with no damage to journals or lifters. Although the oil definitely had some coolant in it, I caught it well before anything resembling a milkshake formed.

            With any luck, I will have this thing back in a couple of weeks and be on the road again. I need to finish refreshing my spare wire harness (trim ignition leads for COP + crimp on new SPT terminals, integrate WBO2 controller into harness, integrate MAF into harness) and reinstall all of my data logging goodies into the ECU (a fair bit of soldering), order EGT probes and decide whether or not I actually want to use the RHD engineering flywheel. The lightweight flywheel in there now (11lb M20 FW) idles fine, but taking another 4lbs off is tempting. For now I may just get it all back together and swap flywheels in the future after all the tuning is done.

            Comment


              #51
              Sounds like MM got this done relatively quickly. Looking forward to seeing some reinstallation photos and hearing your impressions of the newly built motor.

              Comment


                #52
                sounds like a bit of common sense prevailed with the rod and pistons as money is better spent elsewhere IMO. how come it needed new seats vs just a new VJ? 0.0029 to .0032 seems like a decent amount for a 4032 slug?

                https://metricmechanic.com/wp-conten...ance-Chart.pdf
                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


                  #53
                  Originally posted by digger View Post
                  sounds like a bit of common sense prevailed with the rod and pistons as money is better spent elsewhere IMO. how come it needed new seats vs just a new VJ? 0.0029 to .0032 seems like a decent amount for a 4032 slug?

                  https://metricmechanic.com/wp-conten...ance-Chart.pdf
                  That document is fairly old, and a lot of the parts and techniques they use have changed since then (such as no longer honing with 400 grit in most cases). The 0.0032 - 0.0029 values were verbal over the phone, so either they go a little looser these days or Jim misspoke. The PDF you linked has the Rally M42 listed as 2.0L, which indicates that it is probably based on obsolete bottom end assemblies and techniques that they have moved on from. Back in 2012 when they built the first one for me, the 2.1L Rally engine was listed as having a 0.003" nominal clearance IIRC, and it was noted that it was about 0.001" more than the Sport engine since they had cranked up the compression ratio on the Rally engine at that time. The Rally M42 bottom end parts started evolving pretty rapidly back around that time, and I guess I ordered things up late enough that I got in on much more updated parts than they had been using for their first Rally M42 design for Sam (FebiGuibo, RIP). Anyway, Jim had mentioned that they need to update some documentation, which is tough when they are always at 100% just building their product.

                  The existing valve seats were OK, but MM has come up with some new shape that they claim a 2% increased flow with. It was more of a "hey we also did that for you" thing.

                  As far as I can tell, they want to see this engine again about as much as I want to have to ship it to them again, and they have been going through to make it 99% match what they would ship today if I had placed a new order.

                  Comment


                    #54
                    Originally posted by mike.bmw View Post
                    Sounds like MM got this done relatively quickly. Looking forward to seeing some reinstallation photos and hearing your impressions of the newly built motor.
                    Yup, it has been fast. When I shipped it out there in November, they had 17 engines already queued. We lost a month or more to the holidays (they close some of that time, Wiseco and other suppliers close other times, etc) and they needed to clear part of the backlog while we planned everything out. I believe that they fully disassembled my engine around a month ago while they worked on other builds and got stuff ordered. Once my engine was on deck for inspection, machining and building, it was all hands on deck. They prefer to go 100% on a single engine at a time to keep up momentum and focus I guess.

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