GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Mechanical - 7.8L 🢒 Piston Selection
  1. Measure the cylinder liner outside diameter.

    2. Object Number: 736700 Size: SH
  2. Place the bore gage 20 mm (0.79 in) below the gasket surface.
  3. Replace the cylinder liner if not within the specifications:
    4. • Grade 1: 117.981-117.990 mm (4.6449-4.6453 in)
    • Grade 2: 117.991-118.000 mm (4.6453-4.6457 in)
    • Grade 3: 118.001-118.010 mm (4.6457-4.64619 in)
  4. When replacing the cylinder liner with a service part liner, select liner grade 1X for factory liner grade 1 and 2, liner grade 3X for factory liner grade 3.

    5. Object Number: 736702 Size: SH
  5. Measure the piston diameter.
  6. Place the micrometer 84.6 mm (3.33 in) below the piston crown, at a right angle to the piston pin bore. The factory measurements are as follows:
    7. • Grade A: 114.920-114.929 mm (4.5244-4.5248 in)
    • Grade B: 114.930-114.939 mm (4.5248-4.5251 in)
    • Grade C: 114.940-114.949 mm (4.5252-4.5255 in)
  7. There are 3 different sizes of pistons to be installed from the factory. The size grades are referred to as "A", "B" and "C".
  8. The size grade letter is stamped on the piston crown. The engine may come with any combination of piston sizes.
  9. Replace the piston. The piston should be the same grade as the cylinder liner.
  10. Pistons are supplied either as part of the cylinder liner set, or separately.
  11. When replacing the cylinder liner, also replace the piston. When replacing a piston separately, be sure that the piston to cylinder liner clearance is within factory specifications.
  12. Measure the piston to cylinder liner clearance.
  13. Subtract the piston diameter from the cylinder liner bore diameter.
  14. Correct clearance is 0.092-0.11 mm (0.0036-0.0043 in).
  15. If the clearance is correct, the piston and the cylinder liner are acceptable for further use.
  16. If the clearance is incorrect, try a new piston.

    17. Important: Never attempt to hone the cylinder liner. Honing may damage the chrome finish on the liners surface.

  17. If the clearance cannot be brought within factory specifications by the use of a new piston, the cylinder liner must be replaced. There are no oversize pistons available.