I'm rebuilding my vr6 after spinning a big end bearing. I bought the motor as a built short block with a set of wossner forged high comp pistons and was told it was bored out to 3.0l at the time. As part of the rebuild I've de glazed the bores and planning to fit a new set of rings...this is where it gets interesting.... So I checked the part number etched onto the piston top. 9053D150...according to wossner that's an 82.5mm giving a displacement of 2.9L. Whilst a little miffed at my loss of 0.1L I rang awesome and orders the rings to go with that piston set. They arrived today so set about checking the ring gap....it was huge! (2-3mm). Very confused I cracked out my vernier (should have at the start I know...) and measured the piston skirt...guess what...83.43mm with a coresponding bore of 83.5mm which gives you 3.0L!... So it looks like I have a set of 3.0L 83.5mm pistons with the wrong part number scribed on! WTF!? Has anyone else had experience of this!? To be sure my vernier was spot in I measured a stock piston which came in bang in 81mm as per spec so confident my measuring equipment is right. Obviously not awesome's fault as they got exactly what I asked for. Gonna give them a call tomorrow to see if they can get in touch with wossner and help clarify what the issue might be.
Exactly. So why does my piston measure up at 83.5!? Only thing I can think is that it's been marked up with the wrong part number!? Unlikely I know but can't think of any other explanation!
Sounds like the wrong number stamped on the piston. Irrespective of the number on there currently, 83.5mm is 83.5mm! Never had an issue with my low comp Wossner pistons though. Did you deglaze the bores with a Flex-Hone? I always find oil consumption to be quite high after using those things. Ideally the block needs to be machine honed at the correct angle (45 deg IIRC), but it's not cheap.
