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Need advice from experience for an M42 rebuild

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    #76
    yikes, thanks for the heads up bmwman91. i'll check the condition of that part when i get home.

    i am starting to get nervous about a lot of these parts thats need replacement that are NLA. i did a search on that part number and there are used parts on ebay and ecstuning/tunermotorsports for new but for $500ish.

    i even looked for the timing sprockets and those are becoming scarce too. is there any point during a timing rebuild to reuse the sprockets, like can it be inspected and deemed still good or is it a must-replace type part at this stage in the teardown?

    Comment


      #77
      The sprocket thing has been a point of contention in the community. My short answer is that, for the most part, the sprockets should probably last forever.

      For a long time it was conventional wisdom among M42 owners that you should always replace the sprockets, and that any sprocket with sharp/pointy teeth was "badly worn." I used to think that was the case as well. After a long conversation with Jim Rowe who owns Metric Mechanic, I stopped thinking that. There were multiple manufacturers of the sprockets, and some simply had sharp teeth rather than square ones. Beyond that, no properly maintained engine would ever have occasion for the chain rollers to come up against the square tips anyway. The chain & teeth simply do not mesh like that.

      So unless your sprockets are showing gall marks, pitting, major loss of metal or other major signs of distress, I would just reuse them and save some money.

      As for the damper, I'd buy a new one. All of the used ones are old as hell by now. Unless a seller is willing to take a photo of the production date which is molded into the back side of the rubber ring, and that date stamp is from the last <10 years, I would not do it. www.getbmwparts.com is a better place for OEM parts, BTW. ECS, Turner & Pelican used to be good, but they are all now owned by the same not-so-great management company. Very often getbmw has better prices on things, at least for true Genuine BMW, which is the only thing they sell. Not everything matters if it is "Genuine" but I would try to keep all engine bits that way.

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        #78
        Just dropped off the block (with lower timing case cover and oil pan in tow) at the shop today. I hope the damage wonít drive me off this project.

        I got home and checked the condition of my sprockets and they donít look pointy. I also looked at the vibration damper and it looks like it is still in good condition. I forgot to take a pic of the sprockets in the lower timing case but Iíll inspect that when it comes back.

        Here are the pics, tell me what you think:




        Comment


          #79
          The sprockets look good.

          For a part produced in early or mid 1990, the damper also looks OK, but it is hard to tell from the photos. With your hands, grip the outer metal toothed ring and use your thumbs to try to separate the inner metal hub. Do this on a few places on the perimeter, from both sides, and keep an eye out for indications that the rubber has cracked. You should not really be able to move anything at all if it is fully intact.

          Maybe mine bit the dust because I rev the engine to 7500RPM pretty regularly lol (fully built 2.1L M42).

          Comment


            #80
            luckily, i put some pressure on the damper and it has a lot of resistance. so thankfully those are areas i can save money on.

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              #81
              so i was researching more on replacing the timing components and i ran across a thread of swapping it to an late m42/m44 timing case?

              would this be cheaper than replacing all the original m42 pieces since parts are more avaialble? i also read its more reliable due to deflector vs idle gear?

              i found a list of parts needed on m42club:
              Lower Timing Chain Case - 11141739699
              Gasket, case to block - 11141743032
              Deflection Rail - 11311739130
              M6x35 Head ScrewsX1 for deflection rail - 07119919824
              Bottom deflection rail - 11311734694
              M6x25 screws X2 for bottom deflection rail - 07119919926
              M6X25 Washers X2 - 07119931044
              Gasket set, TC cover - 11141247633

              do i leave the upper timing case all original?

              Comment


                #82
                I 100% endorse swapping to the 1994-1995 M42 timing case. The deflector sprocket in the original E30 design is crap and a time bomb. It is what did in my original engine.

                It is a direct swap using the parts you listed.

                The gasket PN was updated to 11141739868. Other than that, everything should be exchangeable between the old & new desgn. Just make sure that the top bolt for the long driver's side guide is 45mm long. When the design was updated, the old rail had a 40mm bolt, and using it with the newer one often leads to stripped threads in the head.

                Comment


                  #83
                  i guess this is the biggest ticket item: Lower Timing Chain Case - 11141739699 which 370-400 that bolts to the block, does it use the same front cover that my m42 uses?

                  Comment


                    #84
                    I'd try to buy a used one, honestly. It would likely be under $100. And yes, same outer covers.

                    Comment


                      #85
                      i was able to obtain a late m42 lower timing case for a fair price. thanks bmwman91 for the tip.

                      the block is at the shop and i am just waiting to hear back from them with a quote after they tear it down. i feel like this is a make or break point. i was doing a lot of online research regarding the bottom end rebuild. when i took it out, the cylinder walls had the cross hatch marks and did not show any marring, with high mileage i am guessing they would hone the cylinder walls and assume no need for boring out any material. as i am trying to keep costs as low as possible. what can i do to save on the costs? the shop would deep clean it. i dont have the measuring tools, so i would have the machine shop replace the crankshaft and rod bearings with the appropriate set. would i be able to reuse the stock pistons, install a new set of piston rings, new rod cap bolts at home to save on labor costs? anything else i am missing?

                      Comment


                        #86
                        Originally posted by JonsE30 View Post
                        i was able to obtain a late m42 lower timing case for a fair price. thanks bmwman91 for the tip.

                        the block is at the shop and i am just waiting to hear back from them with a quote after they tear it down. i feel like this is a make or break point. i was doing a lot of online research regarding the bottom end rebuild. when i took it out, the cylinder walls had the cross hatch marks and did not show any marring, with high mileage i am guessing they would hone the cylinder walls and assume no need for boring out any material. as i am trying to keep costs as low as possible. what can i do to save on the costs? the shop would deep clean it. i dont have the measuring tools, so i would have the machine shop replace the crankshaft and rod bearings with the appropriate set. would i be able to reuse the stock pistons, install a new set of piston rings, new rod cap bolts at home to save on labor costs? anything else i am missing?
                        Just did the timing case on mine, check out my thread, highlighted the bolts and found the torque specs. Just make sure to use the late model metal gasket that bmwman said: 11141739868
                        1991 BMW 318i AlpinweiŖ II Slicktop 231,000 Miles Build date: Wednesday, 1/30/1991
                        2003 BMW Z4 2.5i Sterlinggrau Metallic 112,000 Miles Build Date: Monday 12/9/2002

                        Comment


                          #87
                          Got a status update on the block from the shop. The block got torn down and inspected crank is good, rods can be recondition but cylinder walls need to bored and I will need new oversized pistons. He is still preparing a quote/estimate but now I have an idea what Iím in for but hopefully all you m42 gurus can help guide me to the next step.

                          As I was trying to keep costs low, would it be possible to reuse the stock piston and just have a slightly larger ring gap? Or does it HAVE to be a new piston/ring set?

                          I see a bunch of forged piston options which are a bit pricey. Are they are non forged alternatives like the oem one but for the larger bore size? Is there another bmw engineís piston I can use with the recondition connection rods?

                          I donít plan on racing, tracking etc. I just want a dependable reliable rebuild that I can drive on 2-3 times a week so I donít need all the high performance spec but if prices are all on level playing field Iíll opt for whatever is better reliability in the long run.

                          Main bearing cap bolts can be reused?
                          Buy new connecting rod bolts?
                          Have the shop install the new crank bearings (upgrade to that 360 full thrust bearing I keep reading about from the m50)?

                          Thanks in advance.

                          Comment


                            #88
                            Consider displacement increases now. Look at what folks have done to get a sub 2.0L M42, and many have used other than M42 fitment BMW pistons, but YMMV.

                            Anything that's TTY should be replaced, and I'd get new rod bolts for peace of mind. Might as well spend $40 now than 2k later.

                            The bearing surface is about the oiling groove, not additional thrust bearings.

                            Basically, let your machinist tell you what size items you can/should use and then you can explore getting parts.

                            Comment


                              #89
                              Originally posted by JonsE30 View Post
                              Got a status update on the block from the shop. The block got torn down and inspected crank is good, rods can be recondition but cylinder walls need to bored and I will need new oversized pistons. He is still preparing a quote/estimate but now I have an idea what I’m in for but hopefully all you m42 gurus can help guide me to the next step.

                              As I was trying to keep costs low, would it be possible to reuse the stock piston and just have a slightly larger ring gap? Or does it HAVE to be a new piston/ring set?

                              I see a bunch of forged piston options which are a bit pricey. Are they are non forged alternatives like the oem one but for the larger bore size? Is there another bmw engine’s piston I can use with the recondition connection rods?

                              I don’t plan on racing, tracking etc. I just want a dependable reliable rebuild that I can drive on 2-3 times a week so I don’t need all the high performance spec but if prices are all on level playing field I’ll opt for whatever is better reliability in the long run.

                              Main bearing cap bolts can be reused?
                              Buy new connecting rod bolts?
                              Have the shop install the new crank bearings (upgrade to that 360 full thrust bearing I keep reading about from the m50)?

                              Thanks in advance.
                              you'll almost certainly need replacement pistons to keep the piston to wall in spec by the time the bores are trued up properly, sounds like the machinist advised this? BMW sell oversized pistons which might be cheaper than aftermarket forged but not by a large amount if at all.

                              you cant beat an OE piston for reliability they are actually engineered for the engine by the piston manufacturers and BMW and tested. a lot of aftermarket forged stuff is not done properly.

                              forged aftermarket pistons are really what you want only if you're building a high performance engine, changing stroke, CR or running more aggressive cams where you need a piston that's physically different to whats available from the OE...

                              new rod bolts are recommended, main bolts bmw seem to say to replace them for the M42.

                              https://workshop-manuals.com/bmw/3_s...lls_(m40_m42)/
                              Last edited by digger; 07-16-2019, 05:14 PM.
                              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


                                #90
                                so i got a call back from the shop after the tear down and the quote i was given was pretty much what to i expect for a rebuild, i just of course wish it was lower.

                                once it comes back i will finish re-assembling the head, and i'd like to prepare for it to mate to the block.

                                i removed the camshafts, trays and lifters from the old head to transfer to the re-valved head.

                                do i need to prime the lifters with oil and bleed it with vacuum pump?
                                do i need to use assembly lube on the walls of the cam tray where the lifters slide in?

                                i was looking for a head gasket and found a "cylinder head gasket set" from elring on ecstuning that looks like it has all the seals and gaskets from the block surface deck up. except the 10 head bolts and 10 head bolt washers. is this good for just a basic street car?

                                i mainly here to stay away from victor reinz but hear elring is a good alternative.

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