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Turbo M20 2.8L Stroker w/ 135mm rods

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    Turbo M20 2.8L Stroker w/ 135mm rods

    I'm in the process of building my 2.8L M20 stroker for turbo application, and I just need to know if this recipe will work.

    M20B25 Block
    M52B28 2.8L 84mm Crank and ARP Main Studs
    Crank Spacer
    FCP Forged H Beam 135mm rods w/ ARP Rod Bolts
    Calico Coated Late Model Rod and Main bearings

    I am going to have Forged Pistons made once I know how large I need them to be. I am trying to get away with 84mm stock size so I dont run into any issues with boring, and also I would like to use a square engine setup.

    My main concern is that I do not see many people running 135mm rods with the M52 crank. I usually see the 130mm rods. So what is the solution? Do I just tell the company that is making the pistons that I need them to be able to fit 135mm rods? Is it that simple?

    Thanks in advance
    Last edited by SLEEPYDUB; 10-30-2017, 03:18 PM.
    - AXIS POWERS - 2JZ E30 Build
    Current Project - 87 325is 2JZ Swapped with M4 DCT

    #2
    Your piston compression height would just need to be 5mm less than it would be with if you used a 130mm rod. I don't see why that should be a problem, given the desired engine specs (desired compression ratio, stroke, rod length, deck height, combustion chamber volume, etc) the manufacturer will be able to make you the piston you need, and pistons made to suit the 885 head's combustion chamber are readily available so that won't be a problem.

    IG @turbovarg
    '91 318is, M20 turbo
    [CoTM: 4-18]
    '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
    - updated 1-26

    Comment


      #3
      That's a good plan. We use the 130mm rods so we can use shelf pistons, but that changes when we go forged pistons. The longer throw cranks is where the issue lies and we are forced to run shorter rods since the wrist pin can only go so high before it interferes with rings.

      Your bearing choice is going to depend on the block, you can't just use late bearings in an early block. The early bearings have an oil groove all the way around both shells, the late have a smooth cap bearing and grooved upper shell. The early blocks will have one large locating tang on each shell, so technically it uses all the same bearings whereas the late models have a two tang shell that is dedicated to the cap side. (and this design carried all the way up to s54).
      john@m20guru.com
      Links:
      Transaction feedback: Here, here and here. Thanks :D

      Comment


        #4
        Originally posted by ForcedFirebird View Post
        That's a good plan. We use the 130mm rods so we can use shelf pistons, but that changes when we go forged pistons. The longer throw cranks is where the issue lies and we are forced to run shorter rods since the wrist pin can only go so high before it interferes with rings.

        Your bearing choice is going to depend on the block, you can't just use late bearings in an early block. The early bearings have an oil groove all the way around both shells, the late have a smooth cap bearing and grooved upper shell. The early blocks will have one large locating tang on each shell, so technically it uses all the same bearings whereas the late models have a two tang shell that is dedicated to the cap side. (and this design carried all the way up to s54).
        Thank you for that bit of info. Looks like I may need a new set of bearings if this block is an early. But it came out of a plastic bumper car so Im sure its the late model.
        Last edited by SLEEPYDUB; 10-30-2017, 03:19 PM.
        - AXIS POWERS - 2JZ E30 Build
        Current Project - 87 325is 2JZ Swapped with M4 DCT

        Comment


          #5
          Have a look at this spreadsheet from my Das Beast build. I used the "Std Comp Stroker" formula. .You can tweak numbers as desired.

          "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

          1987 E30 3L Turbo Stroker Das Beast
          2002 E39 M5

          Comment


            #6
            Note it is better to use 206.0-206.2 or thereabouts for deck height as it's the stack height that is 206.7mm not the deck. This is why stock piston sits above the deck.

            Also imo you are better off buying Pistons a bit oversized get fresh bored and honed to suit.
            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


              #7
              Originally posted by dvallis View Post
              Have a look at this spreadsheet from my Das Beast build. I used the "Std Comp Stroker" formula. .You can tweak numbers as desired.


              IMO, those are both "low comp" stroker examples. Why not take the block deck down another .5mm (~.020")? Since the pistons are already below deck in this situation, further adding quench with a thicker gasket is a power-robber, specially when going boost. I have confidently pushed many 9.6:1 SCR engines well above 1.5 bar and had nothing but good results. Besides bragging rights for the psi-gauge number 8.3:1 is not better for turbo than 8.8:1 - sorry. More boost does not always mean more power. The more power the engine cam make N/A the better - even when adding boost. The internet has been passing this bad/wrong info around for years. The only drawback for higher compression is your tune needs to be better spot-on then with lower comp, but the benefits out-weigh that small handicap.
              john@m20guru.com
              Links:
              Transaction feedback: Here, here and here. Thanks :D

              Comment


                #8
                Originally posted by ForcedFirebird View Post
                IMO, those are both "low comp" stroker examples. Why not take the block deck down another .5mm (~.020")?
                What if he decides in the future to go to a 3-3.1-3.2L stroker (as I did)?
                Will the decking of the block seem a very good solution then?
                CR is achieved through pistons, not through decking of the block or shaving the head.

                Comment


                  #9
                  Originally posted by apostate View Post
                  What if he decides in the future to go to a 3-3.1-3.2L stroker (as I did)?
                  Will the decking of the block seem a very good solution then?
                  CR is achieved through pistons, not through decking of the block or shaving the head.
                  Um, when your pistons are .5mm below deck, it's got 2.3mm quench seeing you have another 1.7mm in head gasket material, that puts the pistons 2.3mm below the block deck. You build the block to suit and if done correctly the engine will last a good long time, you don't leave power on the table "just in case I want to rebuild it again". The m20b25 was actually designed around the quench/swirl and the reason a flat piston b27 eta with an 885 head will never make the power of a b25.

                  Besides, m20 block are cheap as chips, why would you try and save $100 on a multi-thousand dollar build? Crap, I have 6 of them on the pallet to be machined, have 4-5 spare rotating assembly cores, 4-5 good running stock m20's, piles of heads etc - and that's just the m20's. Won't go into the mountain of 24v work piled up here.

                  You seem to keep rebutting my posts (as well as Digger's), but I do build these day in and day out for a living, and have owned an e30/m20 specialty shop for almost a decade (have been rebuilding engines in general since 96, once I bough an e30 in 07, that just so happens the direction my shop took). I measure these engine daily, dyno them several times a year and have taken the time to flow the heads on my bench, figured out the best combinations, and my engines are lasting and have racers on podiums etc. My Spec rebuilt 2.5 engines make more power than is allowed in the series, even.

                  I don't just re-iterate stuff I read on the internet. I have developed my knowledge of these engine by building them, testing them, and racing them, not reading about them.

                  Originally posted by apostate View Post
                  That's my point too.
                  Internet is a great place to learn from but there are people there who know a thing or two about alloys. And about metallurgy science.
                  Otherwise, it is great to learn from the internet.
                  Last edited by ForcedFirebird; 10-31-2017, 01:10 PM.
                  john@m20guru.com
                  Links:
                  Transaction feedback: Here, here and here. Thanks :D

                  Comment


                    #10
                    Then use a thinner mls gasket to tune the piston to head clearance and avoid having to take a lot off the block

                    The Pistons don't sit 0.5mm below deck with that combo, it's 0.5mm below stock which is already above. Not optimising the piston to deck clearance is doing half a job
                    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


                      #11
                      Originally posted by digger View Post
                      Then use a thinner mls gasket to tune the piston to head clearance and avoid having to take a lot off the block

                      The Pistons don't sit 0.5mm below deck with that combo, it's 0.5mm below stock which is already above. Not optimising the piston to deck clearance is doing half a job
                      True, could use thinner gasket, Cometic actually offers a .040" which will get you close, but again it's a moot point since a $200 gasket costs more than a replacement block. .5mm is not as much as one thinks to take off a block (it often takes .1-.2mm to square and fresh the deck anyways).

                      Unlike the budget b27 build which pulls 5mm off and can move the cam timing. If you look at an m20 block it has a "10" stamped on the front corner as a machining limit guide. When machining it the "1" comes off first, then the "0" which happens right before .5mm, so realistically you are only a very slight past factory machining limit for a rebuild.

                      Excuse the imperial measurements, but all my measuring tools are. I recently took .010" off a block and the head was only .004" shorter than stock and I still had .057" quench with the stock gasket (found the domed pistons most power at .037"). The "0" was still showing clear as day. I let the engine go since we were close to race day and it still made more power than Spec allows.
                      john@m20guru.com
                      Links:
                      Transaction feedback: Here, here and here. Thanks :D

                      Comment


                        #12
                        Originally posted by ForcedFirebird View Post
                        ...

                        You seem to keep rebutting my posts (as well as Digger's), but I do build these day in and day out for a living, and have owned an e30/m20 specialty shop for almost a decade (have been rebuilding engines in general since 96, once I bough an e30 in 07, that just so happens the direction my shop took). I measure these engine daily, dyno them several times a year and have taken the time to flow the heads on my bench, figured out the best combinations, and my engines are lasting and have racers on podiums etc. My Spec rebuilt 2.5 engines make more power than is allowed in the series, even.

                        I don't just re-iterate stuff I read on the internet. I have developed my knowledge of these engine by building them, testing them, and racing them, not reading about them.
                        No, just trying to deliver the obvious commonsense to the regular user.
                        You might have built a lot of engines but it doesn't mean that you built them right, no? It is a great mistake to deck the block and I am sure a lot of people will regret your advice at a later stage when they decide to go after a bigger displacement after finding that there are better options than 2.8L.
                        With regard to Digger, are you his assistant/secretary? I don't mind talking to the "staff" if the "boss" is alright with it.

                        Comment


                          #13
                          Man this is getting way over my head, but I'm glad that you guys have responded so I can learn a little bit.

                          I took my block to the machine shop today. He is going to acid bath it and mic it this week. Once he measures the bore I will order the proper sized pistons, hopefully I can stick with the standard 84mm bore, as I'd really like to have a square engine.

                          According to you guys there is so much more that goes into this however, and quench/swirl and Deck height in relation to the pistons are something I am not too familiar with.

                          What do I need to do as far as quench/swirl? Just tell my piston manufacturer I am using an 885 head and they will handle it? Do they need to know my deck height or something?

                          Also, I think I'd like to go with 9:1 compression, being that I will be full time E85 and can take advantage of the higher compression without worrying about too much detonation. Do you guys see any downsides to this? Or suggest a better ratio?

                          If I haven't mentioned it before, I will be attempting to make 500-600whp on this engine, and It will be used in a car that will see a few drift events a year.

                          Thanks again guys!
                          - AXIS POWERS - 2JZ E30 Build
                          Current Project - 87 325is 2JZ Swapped with M4 DCT

                          Comment


                            #14
                            Originally posted by apostate View Post
                            No, just trying to deliver the obvious commonsense to the regular user.
                            You might have built a lot of engines but it doesn't mean that you built them right, no? It is a great mistake to deck the block and I am sure a lot of people will regret your advice at a later stage when they decide to go after a bigger displacement after finding that there are better options than 2.8L.
                            With regard to Digger, are you his assistant/secretary? I don't mind talking to the "staff" if the "boss" is alright with it.
                            Also common sense is you can use a thicker mls gasket to if you have a good block you want to reuse and getting another is not an option. They aren't cheap but neither is a set of new forged Pistons and another full rebuild.
                            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


                              #15
                              Right. But you should have addressed this to the EngineBuildingBird, not to me. I am on your side on this issue.

                              Comment

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