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Fitting Pistons

  1. With piston and rod assembly removed and disassembled as previously outlined, thoroughly clean piston. Check ring side clearance, side clearance should be no more than 0.006" (0.15mm). Check ring end gap in cylinder against specifications.
  2. Check fit of piston in cylinders with rings removed. There should be no more than 0.006" (0.15mm) clearance. Pistons are available in 0.0079" (0.2mm) 0.0157" (0.4mm) and 0.0236" (0.6mm) oversizes. There are three classes of standard size pistons. If piston is replaced, one of the same class must be installed. Class of piston is stamped on bottom of piston.
    Fig 1: Using a Feeler Gauge to Check Piston-to-Cylinder Wall Clearance
    G09334412Courtesy of NOT AVAILABLE
    PISTON CLASS SPECIFICATION

    Application (1)Size
    X1/9
    Class A 3.3827-3.3831" (85.92-85.93 mm)
    Class C 3.3842-3.3846" (85.96-85.97 mm)
    Class E 3.3850-3.3854" (85.98-85.99 mm)
    (1) Measured at 1.35" (34.3 mm) from piston skirt edge.
    PISTON CLASS SPECIFICATION

    Application (1)Size
    128
    Class A 3.3827-3.3831" (85.92-85.93 mm)
    Class C 3.3835-3.3839" (85.94-85.95 mm)
    Class E 3.3842-3.3846" (85.96-85.97 mm)
    (1) Measured at 1.35" (34.3 mm) from piston skirt edge.
  3. When installing rings, make sure gaps are spaced approximately 120° apart. Assemble piston and connecting rod and install in vehicle as previously outlined.
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