Always check the ring gap before installing the rings. To small a gap
will destroy the engine when the rings heat up and the ends touch.
Performance ring sets often need to be trimmed to the proper
gap..usually 0.003- 0.004 per inch of bore diameter for the top ring,
slightly less for the second ring. Oil rings don't usually need
trimming...but check anyway. Overhaul sets often times don't need
trimming, but check anyway. Unless the engine has been rebored, check
the gap on the least worn section of cylinder wall..probably the bottom
of the bore. Trim with a ring gapper or a very thin abrasive wheel like
that used on a 3" air powered cut off tool. Hand turn the disc on an
arbor with the ring ends on sides of the wheel while supporting the
ring just in from the ends. Turning by hand goes slow enough to keep an
eye on the process. If available, check the factory spec. for end gap.

HotRod wrote:
Actually that sounds like good advice, the "official" tool for
compressing
the piston rings and installing them looks a lot like a thin sheet of
metal
wrapped around the piston and then tightened "Strap / handle". and
then the
piston is pushed down. I did see something on TV the other day about
setting
the gap on piston rings, does anyone have any experience doing
this???