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M42 Stroker Looking for Info

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    M42 Stroker Looking for Info

    I was hoping to get a little more information about a stroker build that I'm planning. I bought a spare m42/g240 and I know I need a m47 crankshaft, but I'm not sure if the engine I get it from would matter. I've seen the e46 and e39 crankshaft. I'm just not sure if either is acceptable.

    I plan on boring the block to 85mm because further down the road this engine will be turbocharged. I'm looking into getting aftermarket forged internals. Would my rods have to be longer to compensate for the longer stroke?

    In terms of CR I would like to keep it at 9:1 or possibly 9.5:1 would this be too much if I eventually go turbo?

    Also, does anyone have any good links for a designing a crank girdle?


    My Daily Driven 318is

    #2
    Both e46 or e39 cranks should be ok, as long its the older model with no trigger wheel on the back.

    See:
    http://bmwfans.info/parts-catalog/E4...bearing_shells

    Versus:
    http://bmwfans.info/parts-catalog/E4...earing_shells/

    The newer crank doesn't have place for the oil pump... thingy.. on the front, pardon my english :D

    The 85mm bore should be ok, but i wouldn't go any more than that.
    Also i would't go with rods less than 140mm cause the rod ratio will go bonkers, the longer the better, altough there's not much room for piston with 87mm troke.

    9,5:1 CR is perfectly fine with forged internals, a good engine management with good tune will save you from that mean knocknock. ;)
    And with ethanol you're even more safe, i run stock 10:1 CR with stock internals with 1.3bar or 18.8psi of boost, RE85 is one hell of a fuel :D
    -89 e30 320i brillantrot m42b20 turbo, street / timeattack
    -97 e36 316iAlpinweiß III Winterbeater

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      #3
      lot of good info in here:
      http://metricmechanic.com/wp-content...ne-Booklet.pdf

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