Formula/Sports Racer
FV
1. #8420 (Phillip Holcomb) Allow 2.0mm piston ring grooves
In section 9.1.1.C.5.C.4, clarify the section by adding as follows:
4. Pistons and wrist pins minimum combined weight without clips or piston rings = 330.0 grams.
a. Piston material shall be cast aluminum with steel inserts.
b. Maximum distance from bottom of wrist pin bore to top of #1 (top) compression ring groove: 1.655
inches (20 mm wrist pin bore assumed).
c. Width of #1 and #2 (compression) ring grooves: .100 +.003 inches or ‐.023 inches (2.0‐2.5mm nominal).
d. Width of #3 (oil) ring groove: .158 +/‐ .003 inches (4.0mm nominal).
e. Wrist pin offset from centerline: .059 +/‐ .005 inches.
f. Eccentricity of piston below the oil ring groove: .012 +/‐ .008 inches. Eccentricity shall be defined as the
difference between the largest diameter and smallest diameter measured at the same distance from the
crown of the piston and below the oil ring grove.