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Thread: BMW m50B25 in to S50B32US+

  1. #1
    Join Date
    Sep 2018
    Location
    Denmark
    Posts
    3
    My Cars
    1994 BMW E36 cab M50B25

    BMW m50B25 in to S50B32US+

    Hi everyone - I`m not sure thisn is the correct forum, but hope you can help me out:

    Im in the process of transforming my 1994 M50B25 (single vanos)motor in to a S50B25 (and then some) clone. The build is rather oldschool - no forced induction but NA.
    I have used the origanal B25 cast iron engine block, that is now cleande, skimmed and bored to fit new 86,4 mm. pistons (JE forged pistons, 11,5:1 CR).
    The head is also checked, skimmed, lightly ported and fitted with new valves, stems, springs etc.
    The eninge block is fitted with M54B30/S50US crank (89,6 mm. /3,5"stroke) and conrods (135 mm.), together with new seals, bearings, pins, rings and everything else.

    My question is:
    The pistons comes 0,91 mm. out of the block - (thats 0,36" over the block) - and I honestly dont feel safe just assembling the motor with a normal head gasket, 1,75 mm (.70") thick - being concerned about piston/valve clearance and the risk of ending up with compression ratio that is too high.
    For me the ideal CR would be appr. 11:1 - but I was not able to find such pistons (in Denmark).

    Do you guys have any advice regarding the head gasket I should use - and to how thick it should be? - I prefer to be on the safe side, rather than ruining my new motor -

    The rest of the build includes reuse of the M50B25 intake manifold, upgrading with enlarged throttle body (68 mm.), 3,5" Euro MAF, AFE cold air intake, nozzles from M54B30 (blue), Euro M3 EVO 3,2 ltr. headers and exhaust - new alloy water pump, alloy wheel for water pump, alloy house for the thermostat, new chains and tensioners - and finally of course the final tune - I belive thats about it - just hope it all turns out well -

  2. #2
    Join Date
    Mar 2012
    Location
    Renton, Wa
    Posts
    5,429
    My Cars
    98 m3

    BMW m50B25 in to S50B32US+

    That sounds a little high I remember 0.6mm above deck. Probably a lot removed from The deck. None the less

    1.75-0.9 is 0.85mm which is still okay for squish.

    Check out je or Athena gaskets. They are a bit thicker.

    Sent from my iPhone using Tapatalk
    Last edited by vollosso; 09-11-2018 at 12:50 PM.
    1989 535i - sold
    1999 M3 Tiag/Dove - sold
    1998 M3 Turbo Arctic/black - current
    2004 Built motor TiAg/Black - Sold
    2008 E61 19T Turbo-Wagon - current
    2011 E82 135i - S85 Swap - current
    1998 M3 Cosmos S54 swapped Sedan - current

    1998 Turbo: PTE6870 | 1.15 ar | Hp Cover, Custom Divided T4 bottom-mount, 3.5" SS exhaust, Dual Turbosmart Compgates, Turbosmart Raceport BOV, 3.5" Treadstone Intercooler, 3.5" Vibrant resonator and muffler, Arp 2k Headstuds | Arp 2k Main studs | 87mm Je pistons | Eagle rods | 9.2:1 static compression, Ces 87mm cutring, Custom solid rear subframe bushings, Akg 85d diff bushings, 4 clutch 3.15 diff, , Poly engine mounts, UUC trans mounts W/ enforcers, 22RPD OBD2 Stock ECU id1700 E85 tune, 22RPD Big power Transmission swap w/ GS6-53

  3. #3
    Join Date
    Sep 2018
    Location
    Denmark
    Posts
    3
    My Cars
    1994 BMW E36 cab M50B25
    I see that VAC Motorsport sell a steel multi layered gasket in (0,8") equals appr. 2 mm. - that would be better then? Although perhaps a bit overkill for a NA motor - and to the fact that I already have one in standard thickness...

    Btw Many thanks for your help - it`s highly appreciated!

  4. #4
    Join Date
    Mar 2012
    Location
    Renton, Wa
    Posts
    5,429
    My Cars
    98 m3
    I wouldn’t run a mls gasket.

    If your measurements are good I think you are fine. You are at the lower limit of squish.

    You should be able to buy an oem gasket that is fractionally thicker. If not check out Athena or je.


    Sent from my iPhone using Tapatalk
    1989 535i - sold
    1999 M3 Tiag/Dove - sold
    1998 M3 Turbo Arctic/black - current
    2004 Built motor TiAg/Black - Sold
    2008 E61 19T Turbo-Wagon - current
    2011 E82 135i - S85 Swap - current
    1998 M3 Cosmos S54 swapped Sedan - current

    1998 Turbo: PTE6870 | 1.15 ar | Hp Cover, Custom Divided T4 bottom-mount, 3.5" SS exhaust, Dual Turbosmart Compgates, Turbosmart Raceport BOV, 3.5" Treadstone Intercooler, 3.5" Vibrant resonator and muffler, Arp 2k Headstuds | Arp 2k Main studs | 87mm Je pistons | Eagle rods | 9.2:1 static compression, Ces 87mm cutring, Custom solid rear subframe bushings, Akg 85d diff bushings, 4 clutch 3.15 diff, , Poly engine mounts, UUC trans mounts W/ enforcers, 22RPD OBD2 Stock ECU id1700 E85 tune, 22RPD Big power Transmission swap w/ GS6-53

  5. #5
    Join Date
    Sep 2018
    Location
    Denmark
    Posts
    3
    My Cars
    1994 BMW E36 cab M50B25
    Great - thanks a lot mate!

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