Measuring Cylinder Bore Diameter - Chevrolet Trailblazer Service Manual

results of this inspection will determine whether the cylinder can be used in its existing size
and condition, or a re-bore to the next oversize is required (or in the case of removable
sleeves, have replacements installed).
Measurements are taken at three locations in each cylinder: at the top, middle and bottom.
Two measurements are taken at each location. One that is perpendicular (ninety degrees)
from the crankshaft centerline and the other that is parallel to the crankshaft centerline.
The measurements are made with either a dial indicator or a telescopic gauge and
micrometer.
Start measurements at the top of the cylinder bore, and proceed to the middle and finally
at the bottom. A total of six measurements will be taken for each cylinder bore.
1. Measure the cylinder as follows:
A. Position the gauge in a cylinder bore near the top.
B. Loosen the gauge lock and allow it to expand.
C. Hold the gauge squarely in the bore, perpendicular (90 degrees) to the
crankshaft centerline.
D. Tighten the lock.
E. Tilt the gauge back to remove it from the bore.
F. Measure the gauge with the micrometer and record the reading.
G. Position the gauge squarely in the same bore parallel (in-line) to the
crankshaft centerline. Repeat steps A to F.
H. Measure the gauge with the micrometer and record this reading.
I. The difference between these two readings is the out-of-round
measurement of the cylinder.
The difference between these measurements will indicate the cylinder wear. The
measurements taken perpendicular (90 degrees) to the crankshaft centerline will typically

Measuring cylinder bore diameter