Piston Ring: Service and Repair

1. Measurement of end gaps:
a. Measure piston ring gap 2 in. from bottom of cylinder bore. An inverted piston can be used to push the rings down to ensure positioning rings squarely in the cylinder bore before measuring.
b. Insert feeler gauge in the gap. The top compression ring gap should be between 0.254-0.508 mm (0.010-0.020 in.). The second compression ring gap should be between 0.508-0.762 mm (0.020-0.030 in.). The oil ring gap should be 0.254-1.270 mm (0.010-0.050 in.).
c. Rings with insufficient end gap may be properly filed to the correct dimension. Rings with excess gaps should not be used.
2. Install rings, and confirm ring side clearance:
a. Install oil rings being careful not to nick or scratch the piston. Install the oil control rings according to instructions in the package. It is not necessary to use a tool to install the upper and lower rails. Insert oil rail spacer first, then side rails.

Second Compression Ring Identification (Typical):

Compression Ring Chamfer Location (Typical):

b. Install the second compression rings using Installation Tool C-4184. The compression rings must be installed with the identification mark face up (toward top of piston) and chamfer facing down. An identification mark on the ring is a drill point, a stamped letter "O", an oval depression, or the word "TOP".

Top Compression Ring Identification (Typical):

c. Using a ring installer, install the top compression ring with the chamber facing up. An identification mark on the ring is a drill point, a stamped letter "O", an oval depression or the word "TOP" facing up.
d. Measure side clearance between piston ring and ring land. Clearance should be 0.074-0.097 mm (0.0029-0.0038 in.) for the compression rings. The steel rail oil ring should be free in groove, but should not exceed 0.246 mm (0.0097 in.) side clearance.
e. Pistons with insufficient, or excessive, side clearance should be replaced.
3. Orient the rings:

Proper Ring Installation:

a. Arrange top compression ring 90° counter-clockwise from the oil ring rail gap.
b. Arrange second compression ring 90° clockwise from the oil ring rail gap.