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    What do you think of these pistons?

    Hey guys, I already made a post about this on the r3v FB group but the seller is now being aggressive towards me and basically saying 95% of people who commented on that thread have no idea what they're talking about.

    To me, when I recieved these pistons, it looked to me as if material was welded around the skirt of the piston near the wristpin entry. The seller claims it is simply casting marks, though from my knowledge casting leaves small divets and doesn't look like a build up of material. 2/6 pistons had similar markings in the same area. The 6 pistons I pulled from my b25 had no markings similar to it.

    I've included photos of both a piston in question and a "normal" looking piston from the bunch I purchased. Please let me know what you think. Click image for larger version

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    #2
    Maybe casting marks but the machining is garbage....if that is indeed casting. Why should one want to install this ? Who is making those? Sent from my iPhone using Tapatalk

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      #3
      Originally posted by zaq123 View Post
      Maybe casting marks but the machining is garbage....if that is indeed casting. Why should one want to install this ? Who is making those? Sent from my iPhone using Tapatalk
      Apparently these are OEM b25 pistons out of a very low mileage motor that were ultrasonically cleaned. Just weird that 2 our of the 6 would have those abnormal marks and that it would pass BMWs quality control.

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        #4
        Sub'd.

        Curious what others think. I have seen hundreds, if not thousands of OE BMW pistons. Both with excessive, and conservative miles. Probably have 5-6 engines worth just in the disassembly bins.
        john@m20guru.com
        Links:
        Transaction feedback: Here, here and here. Thanks :D

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          #5
          Originally posted by GarbageCanE30 View Post

          Apparently these are OEM b25 pistons out of a very low mileage motor that were ultrasonically cleaned. Just weird that 2 our of the 6 would have those abnormal marks and that it would pass BMWs quality control.
          in that case .....who in the world would go through the trouble to weld old piston?? very very unlikely. I've seen a few oem pistons but don't recall that... Can you just ask the seller to exchange this one for you??? Maybe it's 100% ok but why not.... if it makes you sleep better

          Comment


            #6
            Originally posted by zaq123 View Post

            in that case .....who in the world would go through the trouble to weld old piston?? very very unlikely. I've seen a few oem pistons but don't recall that... Can you just ask the seller to exchange this one for you??? Maybe it's 100% ok but why not.... if it makes you sleep better
            Replacement might be difficult as I don't think he has any in similar condition, but we spoke about it. You're right though, it's super unlikely that someone welded them but it's possible they were cleaned up in such a way to make a sale. Just weird that out of 4 sets of 6 OEM pistons I've seen in the last 3 days these 2 are the only ones that made me raise my eyebrows.

            Comment


              #7
              Originally posted by GarbageCanE30 View Post
              Replacement might be difficult as I don't think he has any in similar condition, but we spoke about it. You're right though, it's super unlikely that someone welded them but it's possible they were cleaned up in such a way to make a sale. Just weird that out of 4 sets of 6 OEM pistons I've seen in the last 3 days these 2 are the only ones that made me raise my eyebrows.
              if those would have been custom pistons, I would be very concern since not addressing that area would be a shortcut IMHO. Since those are mass produced pistons........... as long as all important surfaces are looking good, they are most likely ok. Speaking all important surfaces..... how certain are you that the ultrasonic cleaning is all these pistons have seen? Look a little too clean and shiny for just a ultrasonic from what I've seen before. Stock pistons have those tiny lines- machined marks. If they are gone on yours, some abrasive was involved for sure. Also maybe it's just your pictures but all edges are looking a little too smooth....another sign of abrasive?....possibly was used to shave some material and hide any skirt scoring??? I would be concerned about how they were "cleaned" if anything else. Honestly, I would rather buy good used pistons with ALL the carbon on them as a sure proof that no one f***d with them. This way you are able to evaluate they actual condition without any "cleaning" that can mask real problems or creates new ones (shaved edges on ring groves etc.. I would just soak them with kero/diesel fuel and a toothbrush (maybe soft brass brush for very stubborn carbon on the crown), that all they really need. Below is a couple of pictures: top picture of M20 piston that does show some casting marks in that area. (random internet pic. Bottom picture, piston came from my M20B25 (late model). That is how they looked after some kerosene/brush cleaning: no shaved edges, machine marks still visible as well as visible minimal skirt scoring( (I would be surprised to find any used P without any signs of skirt scoring) ... good piston and most importantly no issues are masked. Click image for larger version

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              Last edited by zaq123; 05-20-2020, 07:40 AM.

              Comment


                #8
                As zaq said, there's no critical dimensions in that area. A casting imperfection that doesn't affect operation was probably given a pass at the factory.

                As I said in your email, it appears someone cleaned them up beyond just an ultrasonic bath. This is a used piston I stuck in the ultrasonic cleaner with some degreaser. Note the patterns, which the PO probably was trying to wipe away from the ultrasound. They can be used straight away like this, have used this method to clean pistons many times over the years.

                Click image for larger version

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                And these are straight out of engines, untouched:

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                john@m20guru.com
                Links:
                Transaction feedback: Here, here and here. Thanks :D

                Comment


                  #9
                  Originally posted by ForcedFirebird View Post
                  As zaq said, there's no critical dimensions in that area. A casting imperfection that doesn't affect operation was probably given a pass at the factory. As I said in your email, it appears someone cleaned them up beyond just an ultrasonic bath. This is a used piston I stuck in the ultrasonic cleaner with some degreaser. Note the patterns, which the PO probably was trying to wipe away from the ultrasound. They can be used straight away like this, have used this method to clean pistons many times over the years. Click image for larger version

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                  Good examples there. Pistons like cyl heads ports, just because they are shiny, doesn’t mean they are good or better than before Sent from my iPhone using Tapatalk

                  Comment


                    #10
                    Click image for larger version

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                    Originally posted by zaq123 View Post
                    Good examples there. Pistons like cyl heads ports, just because they are shiny, doesn’t mean they are good or better than before Sent from my iPhone using Tapatalk
                    I'm attaching some comparison pics and other pics of the pistons to hear your opinion. He mentioned to me he also used steel wool to clean them. These pictures show very clearly the area of concern vs a normal looking skirt. The one on the right is very lumpy to the touch even and looks distorted while the others are much cleaner like the one on the left. The cleaning process also concerns me. The main reason I looked for new pistons is due to scoring on my old ones and these do have some scratches, albeit only on the surface, from the cleaning process.

                    Comment


                      #11
                      Yeah, looks like they were chucked in a lathe and rubbed clean. They may be OK, but have someone measure them. If the PO removed any material, you would have been better off using the scored pistons. BMW's like very tight piston to wall clearances (.002mm or .0007" - less than 1/2 thou on a side). PLUS pistons are NOT round. So, if material came off in places it shouldn't you will have an odd fit when the pistons comes up to temperature. When shaving the skirts off the bottoms of the pistons, I indicate them to center, and they are about .010" out of round at room temp (indicator repeatedly moves +/-.005" every 90°).

                      The area you are concerned about isn't as critical as the outsides of them.
                      john@m20guru.com
                      Links:
                      Transaction feedback: Here, here and here. Thanks :D

                      Comment


                        #12
                        Originally posted by ForcedFirebird View Post
                        Yeah, looks like they were chucked in a lathe and rubbed clean. They may be OK, but have someone measure them. If the PO removed any material, you would have been better off using the scored pistons. BMW's like very tight piston to wall clearances (.002mm or .0007" - less than 1/2 thou on a side). PLUS pistons are NOT round. So, if material came off in places it shouldn't you will have an odd fit when the pistons comes up to temperature. When shaving the skirts off the bottoms of the pistons, I indicate them to center, and they are about .010" out of round at room temp (indicator repeatedly moves +/-.005" every 90°).

                        The area you are concerned about isn't as critical as the outsides of them.
                        Thank you as always John for your input! I'll have my machinist measure them and let him be the judge I suppose.

                        Comment


                          #13
                          Originally posted by GarbageCanE30 View Post

                          Thank you as always John for your input! I'll have my machinist measure them and let him be the judge I suppose.
                          What was wrong with your old pistons? P to V contact? You gonna pay a machinist to check pistons?

                          Honestly, if you went as far as removing them, I'd pay the machinist to bore the block +.5mm (instead of sitting there and checking pistons), get brand new BMW oversized pistons for $500-600 (incl. rings, pins etc) and call it a day. As a result, new bores, new pistons and a few more horses thanks to slightly larger displacement.

                          Comment


                            #14
                            Originally posted by zaq123 View Post

                            What was wrong with your old pistons? P to V contact? You gonna pay a machinist to check pistons?

                            Honestly, if you went as far as removing them, I'd pay the machinist to bore the block +.5mm (instead of sitting there and checking pistons), get brand new BMW oversized pistons for $500-600 (incl. rings, pins etc) and call it a day. As a result, new bores, new pistons and a few more horses thanks to slightly larger displacement.
                            Old pistons had fairly deep scuffs on them. They probably didn't need to be replaced immediately but it was a "while I'm in there" type situation haha. That was originally the idea but these basically looked new, saved me the boring part and therefore more coin. I've began to understand saving money is rarely the right choice when building an e30.. lol

                            Comment


                              #15
                              If someone walked in my place and asked to measure some pistons there was questions about, they would be charged about the cost of a 12 pack of good beer. Block boring starts at $300 for .010 over.
                              john@m20guru.com
                              Links:
                              Transaction feedback: Here, here and here. Thanks :D

                              Comment

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