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blackhippie

what piston rings do i need?

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sorry im still pretty new to all this.  i have a 1974 bmw 2002 with 2.0L m10 that i rebuilt.   the engine is been bored out to 2nd oversize(prev owner).  which i didnt know prior to the rebuild.  so i ordered the piston rings from ireland engineering the +.50 ones and the gap is still too big and is burning oil (had to put the engine back together because winter was coming fast.  sorry if im coming off as a dumbass just need to figure out what i need.    the pistons are not flat top the are kinda recessed...

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We need an accurate piston size in order to help you, i.e. 89.22, 89.47, etc. If, for instance, you've got 89.47 pistons and installed 89.22 rings, or have 89.97 pistons and installed 89.47 rings, you'll have a problem. Is the ring gap clearly way too big? Another issue is semantic. 89.22 pistons are not commonly used in the U.S. anymore so some people automatically think 89.97 when they think "2nd oversize." If you simply use the term 2nd oversize for an 89.97 piston, you might be sold a ring set for an 89.47 piston, which would be technically correct

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What Skip said- you need a number. 

 

THAT said, if  +.5  was still too small,  your next option is +1 mm.  There were some +.75 aftermarket pistons (I had one block bored that way once) but that's a very unusual size.

 

And a dish in the piston??  That's way weird.  Sure there isn't some sort of pop- UP instead?

 

t

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sorry im still pretty new to all this
and
and the gap is still too big
Please described the method used to determine the end gap.  Placed a ring in the bore pushing it down with a piston upsidedown so he ring sits square in the hole and used feeler gauges to establish the gap?

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Echoing what JimK said about accurate gap measurement.

 

Is it possible your gaps are adequate, but something else is amiss?  Did you obtain any compression readings?  Double check that the bores are square, i.e., not tapered?  Were the ring gaps staggered?  Oil burning and even poor compression could merely indicate a problem with rings that never fully seated.  The latter possibility can happen if the bores are improperly honed and/or when the compression rings have an extra hard chrome plate, as used to be the case with OE.  Further on that subject of break-in, did you use an oil specifically designed for that purpose?  A synthetic might be great for lubricity and longevity, but maybe not the best thing for seating rings.       

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