Piston to Cylinder Wall Clearance:
Wössner pistons are designed with a special cam
and cylinder design. When measuring for piston to
wall clearance, measure at widest point of piston
skirt from the bottom of the oil ring groove, 90
degrees from wrist pin hole.
Piston to wall clearance is calculated before the
coating is applied to the piston skirts.
Dome to cylinder head clearance need to be
checked prior to assembly.
Valve to Piston Clearance:
Most Wössner pistons are designed with valve
pockets that are deeper and larger than OEM.
These pockets provide adequate valve clearance
under most conditions. It is very important that
valve to piston clearance is checked upon piston
Installation. This is necessary due to many variations
in cams, how much a block has been decked,
or if the heads have been cut or angle milled.
The rings are installed with suitable piston ring pliers,
starting with the lowest ring. Excessive opening of
the rings is to be invoided, since this could lead to
deformation of the rings. If the rings are deformed,
they are not longer able to provide a perfect seal.
Rings that have the mark are to be fitted with the
marking facing upwards towards the piston crown.
Special care is needed for the installation of steel rail
After the spring has been loaded, the rails are to be
mounted so that rail end gaps point towards the
pin hole. When the upper rail is being installed, the
ends of the spring needs to be held together so as
to prevent over-lapping. After this, the lower rail is
to be installed. In the case of pistons with rotation
prevention in the ring grooves, care need to be taken
to ensure that the ring gaps are positioned alongside
the location pins. After the rings have been installed,
the ring gaps are to be spread evenly around the
circumference (for example at 120° intervals for a