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Several methods can be used to measure the amount of taper within a cylinder.
STEP 1
Measure the amount of piston ring end gap in a cylinder. By measuring the end gap at the top of the cylinder, in the ring turnaround area, in the middle, and at the bottom, cylinder taper can be calculated. End gap is measured after squaring the ring with a piston inside the cylinder. A 0.001" (0.0254 mm) increase in cylinder wall diameter will produce approximately a 0.003" (0.0762 mm) increase in ring end gap. A typical maximum taper wear of a cylinder is 0.001" (0.0254 mm) per inch of cylinder diameter, up to 0.005" (0.127 mm) maximum wear in larger cylinders.
STEP 2
Look for loss of crosshatch. Cylinder crosshatch is produced when an engine is manufactured and during reconditioning. The presence of crosshatch on the cylinder wall is important to provide a surface to seat piston rings and to retain oil for piston and ring lubrication. Highly polished liners will not allow residual oil to cling to the cylinder walls, causing scuffing and piston wear. Highly polished liners indicate worn cylinders.
STEP 3
Use a dial bore gauge to measure cylinder taper but not cylinder diameter. These gauges are used when honing or performing other machining processes to ensure that a consistent, symmetrical dimension is produced.
STEP 4
Use a micrometer and inside telescoping gauges. An inside telescoping gauge is used to gauge the cylinder diameter. An outside micrometer is then used to measure the width of the inside telescoping gauge.
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