Originally Posted by
mxwrench
Eduard, you beat me to it!
Stefan, while this ring is normal, it does seem a little low and close to the piston pin bore, and if compression will be able to bleed into there then the effective combustion chamber volume will lower quite drastically. I would like to see the wear ring about 1mm higher up the piston, where the 2nd ring cut is, and the 2nd ring cut .5mm higher (closer to the 1st).
BK
Hi Edward and Wrench,
sorry to be stubborn, but on ALL the other engines I owned (quite a few) I have never seen this before. I know that pistons are tapered, but usually they seal much further to the top. All my NR engines, including the BRB and the very rare NR.12 AAC set I got from Edward, have that ring were they seal on the very top.
This Picco piston does not seem to touch the sleeve above that ring at all, since it is nicely coated with carbon deposits up there, which usually doen't happen.
Also, when you push the piston up the sleeve, there is some resitance about 3 mm before the top and once the piston passed that, it slips up to the top of the piston with very little force. Usually the resistance grows proportionally the farther the piston goes up.
I actually think that there is a problem with the sleeve. It feels like it has a tight spot in it.
Further, both my Picco based engines which have that problem, show the same ring in the same place. Others that run well, don't.