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Rebuild a VW ~2000cc

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  • Ray
    I have a ~2000+ cc VW aero conversion that I want to overhaul. 78.4 stroke and 91.5 mm bore apparently I am using a Limbach Crank. I measured the cylinders and
    Message 1 of 10 , Sep 2, 2008
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      I have a ~2000+ cc VW aero conversion that I want to overhaul. 78.4
      stroke and 91.5 mm bore apparently

      I am using a Limbach Crank.

      I measured the cylinders and pistons and found that they seem to be
      91.5 mm size.

      Anyone know of a source for this size cylinders/pistons/rings ?

      The old pistons have "Mahle" on the casting and they are flat topped.

      I also wondered how the cylinders might interchange if I wanted to go
      to a 90.5mm of 92mm cylinder. Is the outside diameter similar on any of
      these sizes.

      If I went to the smaller 90.5mm cylinders and the case is drilled for
      the 91.5mm are there reducers required or how would I accomodate the
      smaller cylinders(assuming the OD is actually smaller).

      Any assistance or advice would be appreciated.

      Ray
    • Bill Clark
      Ray, No one in the VW automotive world that I have talked to over the past 24 hours has ever heard of a Mahle 91.5mm piston, so either what you have is
      Message 2 of 10 , Sep 3, 2008
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        Ray,

         

        No one in the VW automotive world that I have talked to over the past 24 hours has ever heard of a Mahle 91.5mm piston, so either what you have is aviation-specific, exceptionally rare, or indicates you measured the bore rather than the piston.

         

        The standard is to measure the piston diameter rather than the bore. If it turns out that your pistons are actually 90.5, your case and head bore will accept either the 90.5mm or the 92mm. As obviously there is a sacrifice in cylinder wall thickness to go with the 92mm, some (not I, but all my experience with this powerplant is automotive, not aviation) will say go to 94mm to get the thickness back, others will say never exceed a 90.5mm bore and use stroke for greater displacement, and others will tell you that as long as you have good air flow the 92mm cylinder will work just fine. My experience is that the 90.5’s live where the others don’t, but it is a lot more work to push an old bus down the 110 degree highway at 4K than to twist a propeller at altitude at 2500, so ‘your mileage may vary’.  For what it’s worth, although I don’t have a good micrometer handy, I checked a set of automotive Cima-Mahle 90.5mm cylinders real quickly on the way out the door this morning with a caliper and the OD of the cylinder appears to be dead on 98mm which will get you ‘close’ on determining whether you are likely to be able to drop in a set.

         

        Where do you live? There are a lot of great books out on building a VW motor that will ‘live’, as well as many good VW automotive shops and parts suppliers that are usually more than happy to ‘gab’ about options, but as you are likely already aware will either not sell to you or require LOTS of disclaimers if you mention that your application is an aero engine, and I could likely point you at one that is close to you when I have an idea where that is.

         

        Regards,

         

        BC


        From: AirVW@yahoogroups.com [mailto: AirVW@yahoogroups.com ] On Behalf Of Ray
        Sent: Tuesday, September 02, 2008 8:13 AM
        To: AirVW@yahoogroups.com
        Subject: [AirVW] Rebuild a VW ~2000cc

         

        I have a ~2000+ cc VW aero conversion that I want to overhaul. 78.4
        stroke and 91.5 mm bore apparently

        I am using a Limbach Crank.

        I measured the cylinders and pistons and found that they seem to be
        91.5 mm size.

        Anyone know of a source for this size cylinders/pistons/ rings ?

        The old pistons have "Mahle" on the casting and they are flat topped.

        I also wondered how the cylinders might interchange if I wanted to go
        to a 90.5mm of 92mm cylinder. Is the outside diameter similar on any of
        these sizes.

        If I went to the smaller 90.5mm cylinders and the case is drilled for
        the 91.5mm are there reducers required or how would I accomodate the
        smaller cylinders(assuming the OD is actually smaller).

        Any assistance or advice would be appreciated.

        Ray

      • Steve Bray
        Air boat, use the phrase air boat and it s cool with them. Steve B Jackson, Tennessee ... From: Bill Clark Subject: RE: [AirVW] Rebuild a
        Message 3 of 10 , Sep 3, 2008
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          Air boat, use the phrase air boat and it's cool with them.

          Steve B
          Jackson, Tennessee

          --- On Wed, 9/3/08, Bill Clark <dba4you@...> wrote:
          From: Bill Clark <dba4you@...>
          Subject: RE: [AirVW] Rebuild a VW ~2000cc
          To: AirVW@yahoogroups.com
          Date: Wednesday, September 3, 2008, 2:00 PM

          Ray,

           

          No one in the VW automotive world that I have talked to over the past 24 hours has ever heard of a Mahle 91.5mm piston, so either what you have is aviation-specific, exceptionally rare, or indicates you measured the bore rather than the piston.

           

          The standard is to measure the piston diameter rather than the bore. If it turns out that your pistons are actually 90.5, your case and head bore will accept either the 90.5mm or the 92mm. As obviously there is a sacrifice in cylinder wall thickness to go with the 92mm, some (not I, but all my experience with this powerplant is automotive, not aviation) will say go to 94mm to get the thickness back, others will say never exceed a 90.5mm bore and use stroke for greater displacement, and others will tell you that as long as you have good air flow the 92mm cylinder will work just fine. My experience is that the 90.5’s live where the others don’t, but it is a lot more work to push an old bus down the 110 degree highway at 4K than to twist a propeller at altitude at 2500, so ‘your mileage may vary’.  For what it’s worth, although I don’t have a good micrometer handy, I checked a set of automotive Cima-Mahle 90.5mm cylinders real quickly on the way out the door this morning with a caliper and the OD of the cylinder appears to be dead on 98mm which will get you ‘close’ on determining whether you are likely to be able to drop in a set.

           

          Where do you live? There are a lot of great books out on building a VW motor that will ‘live’, as well as many good VW automotive shops and parts suppliers that are usually more than happy to ‘gab’ about options, but as you are likely already aware will either not sell to you or require LOTS of disclaimers if you mention that your application is an aero engine, and I could likely point you at one that is close to you when I have an idea where that is.

           

          Regards,

           

          BC


          From: AirVW@yahoogroups.com [mailto: AirVW@yahoogroups.com ] On Behalf Of Ray
          Sent: Tuesday, September 02, 2008 8:13 AM
          To: AirVW@yahoogroups.com
          Subject: [AirVW] Rebuild a VW ~2000cc

           

          I have a ~2000+ cc VW aero conversion that I want to overhaul. 78.4
          stroke and 91.5 mm bore apparently

          I am using a Limbach Crank.

          I measured the cylinders and pistons and found that they seem to be
          91.5 mm size.

          Anyone know of a source for this size cylinders/pistons/ rings ?

          The old pistons have "Mahle" on the casting and they are flat topped.

          I also wondered how the cylinders might interchange if I wanted to go
          to a 90.5mm of 92mm cylinder. Is the outside diameter similar on any of
          these sizes.

          If I went to the smaller 90.5mm cylinders and the case is drilled for
          the 91.5mm are there reducers required or how would I accomodate the
          smaller cylinders(assuming the OD is actually smaller).

          Any assistance or advice would be appreciated.

          Ray


        • Ray
          Bill, Thanks for checking it out. I think the outside of the 91.5mm cylinder was around ~97.8 mm if I recall correctly. I guess that is good since the 90.5mm
          Message 4 of 10 , Sep 4, 2008
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            Bill,

            Thanks for checking it out.

            I think the outside of the 91.5mm cylinder was around ~97.8 mm if I recall correctly.

            I guess that is good since the 90.5mm cylinders have a 98mm dia and means I might have to bore it out a slight bit to make them fit.

            Of course its better to have to bore out rather than buy new case and heads.

            Based on the thicker 90.5mm walls that is what I will be getting for my rebuild.

            Does the base of the cylinder seal against the shimms and top of the case?

            Does the top of the cylinder seal against the copper gaskets or the top and sides of the head?

            I wonder how critical is the opening diameter if it is not used for a sealing surface?

            I read something about the different expansion rates of the aluminum head vs the iron cylinder and that when the engine heated up it improved the sealing, but did not mention whether it was against the sides of the cylinder and head or against the copper gasket.

            I guess what I really need to know is that if you put in a 90.5mm cylinder that is 98mm OD how much bigger does the head need to be? 98.01mm?

            Ray
            Riverside County, CA
          • Bill Clark
            Ray, If I were you, I d talk to the Berg boys at Gene Berg Enterprises in Orange. They are the absolute GODs of automotive VW survival and they have tried just
            Message 5 of 10 , Sep 4, 2008
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              Ray,

               

              If I were you, I’d talk to the Berg boys at Gene Berg Enterprises in Orange . They are the absolute GODs of automotive VW survival and they have tried just about everything. You pay through the nose for their parts and machine work, but I have never run across an unhappy customer unless they ignored Berg’s instructions and/or warnings or misrepresented their application, and I’d rather pay high prices for engine parts than face the high cost of litigation any day!

               

              By the questions you are asking it sounds like you are new to building the VW powerplant, so it is better to put you in touch with true experts than to try and bring you ‘up to speed’ via email, but to catch up so far;

               

              • Don’t take my 98mm as gospel since I measured it with a Harbor Freight caliper and without my glasses. I still think you have a 90.5 or 92mm piston already, and I would expect that even if you do have a 91.5 it will use the same bore as the 90.5/92mm use.
              • Back in the really ‘early days’, some of the single port heads used a copper sealing ring against the top of the cylinder, but whether you are using single or dual port heads, with pistons >= 85.5mm it is a machine fit.
              • DON’T machine the case or heads yourself, even if you are the master of all machinists! Take it to a shop that specializes in VW work (and there are plenty to choose from in SoCal!) along with your pistons and cylinders. Even if you don’t stick with what you currently have, at least you’ll know what you’ve got.
              • (Personal opinion) Don’t build a VW aero motor until you’ve had an automotive motor you built live through at least 75K miles (preferably in a Bus, and a Type III (Squareback, Fastback, Notchback) configuration doesn’t count) and a summer trip to Vegas (during daylight hours). Far too many people don’t understand that VW engines are an extremely complicated assemblage of incredibly precise engineering that gives them the appearance of simplicity, and just believe that they ARE simple. In your case, that could be a fatal error.
              • Machining tolerances are critical. So is properly directed and contained cooling airflow of sufficient volume.

               

              One more thing I’ll throw out there…

               

              I’ve been building automotive VW engines for over 30 years, and unless I was building an absolutely rock stock factory spec motor for either an absolutely authentic vintage restoral or a little old lady who didn’t take her car out if the temperature was outside of a 45-78 degree window, I always start with a counterweighted crank and I also ALWAYS send the crank, rods, pistons, flywheel, clutch, and pressure plate to the balance shop. Because of this, I can tell you that I am currently building a new 1776cc (90.5mm Bore and stock 69mm stroke) using the first crank I ever bought in 1976 which now has over 100,000 miles on it and still checks out to the ’10 under’ factory spec I purchased it at. I’ve seen them crack and break too, but only in badly neglected or abused (racing) engines.

               

              I have looked at all of the aero-VW manufacturer’s web sites, and it seems that none of them use counterweighted crankshafts, so I can’t help but wonder why. My best guess is that someone with more experience with a slide rule than these power plants decided that at the RPM range they are anticipated to operate at the benefit isn’t as great as for those of us that cruise down the freeway at 4000+ RPM, but still I come back to my experience of 100,000+ miles and literally zero wear on a horizontally opposed engine. In an attempt to convert to aeronautically worthwhile terms, a quick trip to the calculator says that if the average speed for those miles was 65MPH, which we all know is way too high, that’s 1538 TTSN, or greater than TBO for most if not all 4 cylinder Continental and Lycoming options. Remember the concept that Bob (the other Bob) Hoover espouses; The aero and automotive worlds are SUCH different applications that all of my experience in one may have no value or application in the other. Also, although I try and not answer questions I don’t know the answer to from personal experience, free advise is still worth exactly what you pay for it.

               

              Good Luck,

               

              BC

               


              From: AirVW@yahoogroups.com [mailto: AirVW@yahoogroups.com ] On Behalf Of Ray
              Sent: Thursday, September 04, 2008 7:40 AM
              To: AirVW@yahoogroups.com
              Subject: [AirVW] Re: Rebuild a VW ~2000cc

               

              Bill,

              Thanks for checking it out.

              I think the outside of the 91.5mm cylinder was around ~97.8 mm if I recall correctly.

              I guess that is good since the 90.5mm cylinders have a 98mm dia and means I might have to bore it out a slight bit to make them fit.

              Of course its better to have to bore out rather than buy new case and heads.

              Based on the thicker 90.5mm walls that is what I will be getting for my rebuild.

              Does the base of the cylinder seal against the shimms and top of the case?

              Does the top of the cylinder seal against the copper gaskets or the top and sides of the head?

              I wonder how critical is the opening diameter if it is not used for a sealing surface?

              I read something about the different expansion rates of the aluminum head vs the iron cylinder and that when the engine heated up it improved the sealing, but did not mention whether it was against the sides of the cylinder and head or against the copper gasket.

              I guess what I really need to know is that if you put in a 90.5mm cylinder that is 98mm OD how much bigger does the head need to be? 98.01mm?

              Ray

            • Ray
              Bill, I took your advice and got my new 90.5mm piston/cylinders from GeneBerg balanced and honed by them. I should know in another month how it all comes
              Message 6 of 10 , Oct 20, 2008
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                Bill,

                I took your advice and got my new 90.5mm piston/cylinders from GeneBerg
                balanced and honed by them.

                I should know in another month how it all comes together and works but
                it is looking really good so far.

                I have been following the Great Planes guide for engine work and am
                very pleased with the tips and accuracy that I am now putting into the
                overhaul.

                Its all about tolerences and I am following the guides to the letter as
                a precision builder would.

                Ray



                --- In AirVW@yahoogroups.com, "Bill Clark" <dba4you@...> wrote:
                >
                > Ray,
                >
                >
                >
                > If I were you, I'd talk to the Berg boys at Gene Berg Enterprises in
                Orange.
                > They are the absolute GODs of automotive VW survival and they have
                tried
                > just about everything. You pay through the nose for their parts and
                machine
                > work, but I have never run across an unhappy customer unless they
                ignored
                > Berg's instructions and/or warnings or misrepresented their
                application, and
                > I'd rather pay high prices for engine parts than face the high cost of
                > litigation any day!
              • k_mccune
                This brand of forged pistons was used on some higher end European dirtbikes KTM/Huskvarna come to mind..back in the 80s and 90s. Sorry no VW info, but it may
                Message 7 of 10 , Oct 23, 2008
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                  This brand of forged pistons was used on some higher end European
                  dirtbikes KTM/Huskvarna come to mind..back in the 80s and 90s. Sorry
                  no VW info, but it may help you get a line on what you want.

                  Kevin


                  --- In AirVW@yahoogroups.com, "Ray" <jb92563@...> wrote:
                  >
                  > I have a ~2000+ cc VW aero conversion that I want to overhaul. 78.4
                  > stroke and 91.5 mm bore apparently
                  >
                  > I am using a Limbach Crank.
                  >
                  > I measured the cylinders and pistons and found that they seem to be
                  > 91.5 mm size.
                  >
                  > Anyone know of a source for this size cylinders/pistons/rings ?
                  >
                  > The old pistons have "Mahle" on the casting and they are flat topped.
                  >
                  > I also wondered how the cylinders might interchange if I wanted to go
                  > to a 90.5mm of 92mm cylinder. Is the outside diameter similar on any of
                  > these sizes.
                  >
                  > If I went to the smaller 90.5mm cylinders and the case is drilled for
                  > the 91.5mm are there reducers required or how would I accomodate the
                  > smaller cylinders(assuming the OD is actually smaller).
                  >
                  > Any assistance or advice would be appreciated.
                  >
                  > Ray
                  >
                • Brian & Pat Stone
                  Hi Kevin, Your VW aero conversion may well be a Limbach certified engine, since you say you re using a Limbach crank. (If so, for my own info as I have a
                  Message 8 of 10 , Oct 26, 2008
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                    Hi Kevin,

                    Your VW aero conversion may well be a Limbach certified engine, since you
                    say you're using a Limbach crank. (If so, for my own info as I have a
                    Limbach L2000, what model might yours be?)

                    My overhaul manual for the Limbach L2000 and L2400 doesn't mention the
                    manufacturer of pistons, but says about cylinders:-
                    "The four cylinders of high silicon aluminum alloy with a NICASIL
                    (nickel-silicon carbide Mahle Trademark) coating. These cylinders feature
                    extremely light weight and enhanced cooling characteristics compared to
                    cast iron cylinders".

                    Unless you are committed to increasing your engine's capacity you could
                    always investigate spares from Limbach. In 1987 Limbach Aircraft Corp.
                    was located in Zurich and in Tulsa, OK. See
                    http://www.limbach.de

                    Cheers
                    Brian Stone.
                    _____________________________________________
                    | |
                    | Brian and Pat Stone, Canberra, Australia |
                    | Ph h +61/0 2 6254 5525 m +61/0 413 08 7631 |
                    | stones@... _or_ bjs@... |
                    |_____________________________________________|


                    On Thu, 23 Oct 2008, k_mccune wrote:

                    > This brand of forged pistons was used on some higher end European
                    > dirtbikes KTM/Huskvarna come to mind..back in the 80s and 90s. Sorry
                    > no VW info, but it may help you get a line on what you want.
                    >
                    > Kevin
                    >
                    >
                    > --- In AirVW@yahoogroups.com, "Ray" <jb92563@...> wrote:
                    >>
                    >> I have a ~2000+ cc VW aero conversion that I want to overhaul. 78.4
                    >> stroke and 91.5 mm bore apparently
                    >>
                    >> I am using a Limbach Crank.
                    >>
                    >> I measured the cylinders and pistons and found that they seem to be
                    >> 91.5 mm size.
                    >>
                    >> Anyone know of a source for this size cylinders/pistons/rings ?
                    >>
                    >> The old pistons have "Mahle" on the casting and they are flat topped.
                    >>
                    >> I also wondered how the cylinders might interchange if I wanted to go
                    >> to a 90.5mm of 92mm cylinder. Is the outside diameter similar on any of
                    >> these sizes.
                    >>
                    >> If I went to the smaller 90.5mm cylinders and the case is drilled for
                    >> the 91.5mm are there reducers required or how would I accomodate the
                    >> smaller cylinders(assuming the OD is actually smaller).
                    >>
                    >> Any assistance or advice would be appreciated.
                    >>
                    >> Ray
                    >>
                    >
                    >
                    >
                    > ------------------------------------
                    >
                    > Yahoo! Groups Links
                    >
                    >
                    >
                    >
                    >
                  • HAROLD DIRKS
                    Check out this URL for limbach engines: http://www.limflug.de/ hrdirks ... From: Brian & Pat Stone To:
                    Message 9 of 10 , Oct 27, 2008
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                      Check out this URL for limbach engines:
                       
                       
                      hrdirks
                       
                       
                      ----- Original Message -----
                      Sent: Sunday, October 26, 2008 8:18 PM
                      Subject: Re: [AirVW] Re: Rebuild a VW ~2000cc

                      Hi Kevin,

                      Your VW aero conversion may well be a Limbach certified engine, since you
                      say you're using a Limbach crank. (If so, for my own info as I have a
                      Limbach L2000, what model might yours be?)

                      My overhaul manual for the Limbach L2000 and L2400 doesn't mention the
                      manufacturer of pistons, but says about cylinders:-
                      "The four cylinders of high silicon aluminum alloy with a NICASIL
                      (nickel-silicon carbide Mahle Trademark) coating. These cylinders feature
                      extremely light weight and enhanced cooling characteristics compared to
                      cast iron cylinders".

                      Unless you are committed to increasing your engine's capacity you could
                      always investigate spares from Limbach. In 1987 Limbach Aircraft Corp.
                      was located in Zurich and in Tulsa, OK. See
                      http://www.limbach. de

                      Cheers
                      Brian Stone.
                      ____________ _________ _________ _________ ______
                      | |
                      | Brian and Pat Stone, Canberra, Australia |
                      | Ph h +61/0 2 6254 5525 m +61/0 413 08 7631 |
                      | stones@pcug. org.au _or_ bjs@.... au |
                      |___________ _________ _________ _________ _______|

                      On Thu, 23 Oct 2008, k_mccune wrote:

                      > This brand of forged pistons was used on some higher end European
                      > dirtbikes KTM/Huskvarna come to mind..back in the 80s and 90s. Sorry
                      > no VW info, but it may help you get a line on what you want.
                      >
                      > Kevin
                      >
                      >
                      > --- In AirVW@yahoogroups. com, "Ray" <jb92563@... > wrote:
                      >>
                      >> I have a ~2000+ cc VW aero conversion that I want to overhaul. 78.4
                      >> stroke and 91.5 mm bore apparently
                      >>
                      >> I am using a Limbach Crank.
                      >>
                      >> I measured the cylinders and pistons and found that they seem to be
                      >> 91.5 mm size.
                      >>
                      >> Anyone know of a source for this size cylinders/pistons/ rings ?
                      >>
                      >> The old pistons have "Mahle" on the casting and they are flat topped.
                      >>
                      >> I also wondered how the cylinders might interchange if I wanted to go
                      >> to a 90.5mm of 92mm cylinder. Is the outside diameter similar on any of
                      >> these sizes.
                      >>
                      >> If I went to the smaller 90.5mm cylinders and the case is drilled for
                      >> the 91.5mm are there reducers required or how would I accomodate the
                      >> smaller cylinders(assuming the OD is actually smaller).
                      >>
                      >> Any assistance or advice would be appreciated.
                      >>
                      >> Ray
                      >>
                      >
                      >
                      >
                      > ------------ --------- --------- ------
                      >
                      > Yahoo! Groups Links
                      >
                      >
                      >
                      >
                      >

                    • Ray
                      Yes it is a Limbach L2000 engine. Apparently before I got it someone had replaced the Nikasil cylinders with regular cast iron cylinders. Now that I have
                      Message 10 of 10 , Oct 27, 2008
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                        Yes it is a Limbach L2000 engine.

                        Apparently before I got it someone had replaced the Nikasil cylinders with regular cast iron cylinders. Now that I have discovered that it is not stock, it explains a few things.

                        The stock replacement cylinders are over $2,000 usd.

                        It also has the 7 row VW oil cooler which I think is different from the stock 5 row version.

                        It has an extended aux oil sump as well.
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