1998 E36 328i - bore out - Page 5

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    #41
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    For ex, say the 2.5 are 84.12mm and 3.0 are 84.03 (numbers made up, I don't remember the exact diameters). The difference in diameter, added to the bore wear in the 2.5 block could lead to lower compression.


    I would not alter compression it would screw up the p2w ( piston 2 wall) clearance, very important as too big and you will end up with lots of blow by or too tight and the piston when heated will scuff the bore/seize
     
     

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    #42
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    Well, apparently they are pretty much the same diameter. Kiwi328 was kind enough to do the measurements, as he had access to both b25 and b30 pistons.

    So it seems pistons should not be a problem.

    However, compression could still change, as you'll have the whole rotating assembly of the M54B30 with a M50B25 head bolted on top. We'll just have to wait and see.
    There are only two products required to make the universe work properly: Duct tape and WD40. 


    If it moves (and it shouldn't): duct tape. 
If it doesn’t move (and it should): WD40.

    Everything else is just stuff.
     
     

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    E36_turbo (04-10-2011)

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    #43
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    really useful thanks, do u reckon, 0.1 can cause problem ? i think a bigger rings can be fitted.

    such as when u grid the crankshaft, there is the next size up for the crank up to 3 times, 0.01,2 and 3. so i guess u can buy a next level up ring if it exists
     
     

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    #44
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    Nah, I'm pretty sure it will be all right.
    There are only two products required to make the universe work properly: Duct tape and WD40. 


    If it moves (and it shouldn't): duct tape. 
If it doesn’t move (and it should): WD40.

    Everything else is just stuff.
     
     

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    #45
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    I'm not sure how accurate that digital micrometer is. But it was giving the same size for both. I have access to some better quality measuring equipment that I'll be using.
    I'll try get a move on with measuring up the engine. I'm a bit bussy with my other projects
    This has some measurements of the original m54b30 engine http://www.e46fanatics.com/forum/sho...d.php?t=730757
    According Haynes repair manual m50b25:
    Standard bore is-3.3071 inches (84.00mm)
    Standard pistons should be-3.0361 inches (83.98mm)
    Piston to bore clearance 0.0004 to 0.0016 (0.01016 to 0.04064mm)

    As far as I know the m54b30 pistons are the same bore.
     
     

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    E36_turbo (05-10-2011),mistreku (05-10-2011)

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