GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC C-Series Medium Duty Truck B7 🢒 Engine 🢒 Engine Mechanical - 7.4L 🢒 Cylinder Boring and Honing

Cylinder Honing Procedure

    Object Number: 186747 Size: SH

    Notice: Always remove all bearings and components from engine block before cleaning, boring or honing the engine block.

  1. When honing the cylinders, follow the manufacturer's recommendations for equipment use, cleaning, and lubrication.
    2. • Use only clean, sharp stones of the proper grade for the amount of material you remove.
    • Dull, dirty stones cut unevenly and generate excessive heat.
    • Do not hone to a final grade with a coarse or medium-grade stone.
    • Leave sufficient metal so that all stone marks may be removed with fine grade stones.
    • Perform final honing with a fine-grade stone and hone the cylinder in a cross hatch pattern at 45 to 65 degrees to obtain the proper clearance.
  2. During the honing operation, thoroughly clean the cylinder bore.
    3. • Repeatedly check the cylinder bore for fit with the selected piston.
    • All measurements of the piston or the cylinder bore should be made with the components at normal room temperature.
  3. When honing to eliminate taper in the cylinder, make full strokes of the hone in the cylinder. Repeatedly check the measurement at the top, the middle, and the bottom of the bore.
    4. • The finish marks should be clean but not sharp.
    • The finish marks should be free from imbedded particles and torn or folded metal.
  4. By measuring the selected piston at the sizing point and by adding the average of the clearance specification, you can determine the cylinder honing dimension required. Refer to Engine Mechanical Specifications .
  5. When finished, the reconditioned cylinder bores should have less than or meet the specified out-of-round or taper requirements.
  6. After final honing and before the piston is checked for fit, clean the bores with hot water and detergent.
    7. 6.1. Scrub the bores with a stiff bristle brush and rinse the bores thoroughly with hot water. Do not allow any abrasive material to remain in the cylinder bores.
       • Abrasive material may cause premature wear of new piston rings and cylinder bores.
       • Abrasive material will contaminate the engine oil and may cause premature wear of the bearings.
    6.2. After washing the cylinder bore, dry the bore with a clean shop towel.
  7. Perform final measurements of the piston and cylinder bore.
  8. Permanently mark the piston for the specific cylinder to which it has been fitted.
  9. Apply clean engine oil to each cylinder bore in order to prevent rusting.

Cylinder Boring Procedure
  1. Before you start the honing or boring operation, measure all new pistons with the micrometer contacting at points exactly 90 degrees from the piston pin centerline.

    2. Important: If you do not check the cylinder block, the boring bar may be tilted, this may result in incorrect rebored cylinder wall to crankshaft angle.

  2. Before you use any type of boring bar, file the top of the cylinder block in order to remove any dirt or burrs.
  3. Carefully follow the instructions furnished by the manufacturer regarding use of equipment.
  4. When you rebore cylinders, make sure all crankshaft bearing caps are in place.
    5. • Tighten the bearing caps to the proper torque in order to avoid distortion of the bores in the final assembly.
    • The crankshaft must be clear of the boring cutter when you bore each cylinder.
  5. When you take the final cut with a boring bar, leave 0.03 mm (0.001 in) on the diameter for finish honing. This gives the required position to the cylinder clearance specifications. (Carefully perform the honing and boring operation in order to maintain the specified clearances between pistons, rings, and cylinder bores).