Use Plastigauge to quickly and accurately measure clearances of rod and main bearings. Plastigauge is a precisely made thread of wax that spreads out to a predictable width as it flattens between your bearing surfaces. A gauge printed right on the package tells you the exact bearing clearance based on the width of the flattened thread. No expensive measuring tools, no pricey tool recalibration, and no math required! Even pro engine builders with a shop full of measuring tools like to use Plastigauge as a secret double-check before final assembly.
Simply cut a short length of Plastigauge (about 1/2 inch is sufficient) and place it on the crankshaft bearing journal. Install the bearing shell dry and tighten the bearing cap, then remove the bearing cap and shell. You will see that the strip of Plastigauge has flattened out from being squashed between the bearing and the journal. Compare the gauge on the edge of the package to the width of the deformed Plastigauge to see your bearing clearance!
Available in three clerarance ranges:
Green measures from 0.001" to 0.003" (0.025 to 0.076mm).
Red measures from 0.002" to 0.006" (0.051 to 0.152mm).
Blue measures from 0.004" to 0.009" (0.102 to 0.229mm).
Each package contains one 12 inch long piece (enough to do a complete V8 engine). Each package has a metric (mm) gauge on one side and inches on the other side. The gauge pattern repeats every inch or so, which means you can trim the package as you use up the Plastigauge.
Note: Some engine builders recommend removing the flattened Plastigauge residue with a little WD-40 before reinstalling the bearing shell and cap, but the Plastigauge wax is formulated to melt and dissolve completely in engine oil.