| I dont know why exactly. They all made noise with 0.008" taper and a 0.003" piston-bore clearance though and it wouldn't go away under any condition, but it did seem to be of lesser amplitude if the car was run very hard. Obviously this was because the pistons expanded a bit due to the heat and they snugged up a bit in the cylinder. As I said earlier, you could tell by looking at the piston that the area just below the oil ring was not coming into contact with the cylinder, however the upper lands perpendicular to the wrist pin showed signs of wear. This was the indication that there is too much taper in the piston which made its position less controlled. The area below the last oil ring all the way down to the bottom edge of the skirt controls the piston up and down the cylinder; making sure it is not 'wobbling' as the connecting rod swings from left to right in its motion. The area above the oil ring has significantly more taper, in fact on the wiseco's there is a 0.040" taper. This is obviously due to the fact that the crown gets much hotter and its expansion will require more clearance to prevent piston siezing. This taper above the oil ring prevents that section of the piston from effectively controlling piston rock, so the control is left to the area below the oil ring. I think that during the modeling/development phase of these pistons, Wiseco wasn't counting on the under piston oil jets. In fact, their engineers were like, "Oh, we didn't know that, LOL". Since the oil jets keep the piston cool and they were modeling the piston design without them, they were building a lot more taper into them than was necessary and this is what led to a piston that makes noise. This problem goes much further than anyone here would realize in terms of its effect on key players in the industry.. If it means anything, PolyDyne is involved in this fiasco as well and both Wiseco and PolyDyne were taking a beating from Z32 owners running pistons with their original design and complaining of noise - and there were a very large number of people having the problem. Sometimes I can't tell if you are just playfully arguing or if you really mean what you say... I'm just wondering why you have never seen this (if you are for real)... If its just the former, HA! Take that!! ;-)
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12:25:26 01/18/04
