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  1. #1
    04 RXP, 15 GTI SE 155, 00 RX, 02 GTX DI ldmoore87's Avatar
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    951 piston size question

    I have a 951 I picked up cheap with no pistons in it everything looks great including cylinders. So I had them miked and came out to be 89.07mm or 3.507 I converted to inches so if that's wrong it's my fault but I just need to know what size pistons to order. I do have a hone to take a little out if necessary but I really don't wanna have to have them bored. Any help is appreciated. Thanks


  2. #2

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    they need boring to 1.5 mm over pistons.

  3. #3
    04 RXP, 15 GTI SE 155, 00 RX, 02 GTX DI ldmoore87's Avatar
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    Thank you for your response. I've been doing some reading and calculations and here's what I've come up with and I'm no machinist or math wiz so it may be way off but here goes std. Bore 87.91 my cylinders are 89.07 and a +1 piston is 88.91 so I took my cylinder bore size and subtracted the size of a +1 piston and came up with 0.16mm convert that to inches and you have 0.00629 so that leaves about 6 thousands clearance. Again I'm no expert so this maybe way off just really don't wanna have to bore the cylinders. Yay or nay

  4. #4
    Thats a bit much cleareance espeacially if its stock (exhaust,compression) and if you are gona buy new pistons you may experience premature piston failure clearence should be .003-.004 depending on forged or cast pistons I beleive ProX makes an 89.5mm piston so you might beable to hone it to 89.5(that includes piston cleareance) but you may need to open the combustion chamber of the head to better fit the the larger piston to get the best squish VS compression ratio for pump gas

  5. #5
    Myself's Avatar
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    It all depends on the piston. WSM or SBT actually call for .006 or more for clearance. I wouldn't be scared to run it at .006 if everything else is in good shape. The bigger bore pistons tend to "grow" a little more than the smaller ones anyway.

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