S&S Cycle Piston Rings - Manual (Page 3)

3
5- If your piston application uses oil ring support rails, install ring
support rail in front piston so that the end gap is toward the rear
of the cylinder (90° from wristpin). Install ring support rail on rear
piston so that the end gap is toward front of the cylinder (90° from
wristpin). The dimple in the ring must face down and be installed
in the gap above the wrist pin on both pistons. See picture below.
6- Ring Gap Placement
A- Oil ring
1- Expander gap must be in center of thrust face (rear of
piston), or 90° from wristpin.
2- Bottom rail gap should be approximately 1.5" or 45° to right
of expander gap.
3- Top rail gap should be approximately 1.5" or 45° to left of
expander gap.
NOTE: Confirm that ends of expander do not overlap during installation.
Properly installed expander will appear larger than piston but will
compress when cylinder installed.
B- Top compression ring gap should be 135° or approximately 41⁄2"
to left of oil expander gap.
C- Second compression ring gap should be 135° or approximately
41⁄2" to right of oil expander gap.