Plastic Gage Method for Connecting Rod Bearings

Important:  When bearings are removed, NEW bearings must be installed during reassembly.

1. Install the connecting rod bearings (4) into the connecting rod (3) and the connecting rod cap (5).
2. Using rubber fuel line over the connecting rod bolts, install the piston and connecting rod assembly onto the crankpin journal.
   Fig 1: Connecting Rod, Bearings & Cap

   Courtesy of GENERAL MOTORS CORP.
3. Install the gaging plastic the full width of the crankpin journal.
   Fig 2: Gaging Plastic Installed On Crankpin Journal

   Courtesy of GENERAL MOTORS CORP.
   NOTE: Refer to FASTENER NOTICE in Cautions and Notices.

   Important:  Use the original connecting rod nuts for clearance measurement. During final assembly, new connecting rod nuts must be used to obtain correct fastener tightening.

4. Install the connecting rod cap and the original, used, nuts.

   Tighten 

   Tighten the connecting rod nuts to 30 N.m (22 lb ft). Tighten the connecting rod nuts an additional 90 degrees.

5. Remove the connecting rod nuts and cap. The gaging plastic may adhere to either the crankpin journal or the connecting rod bearing surface.
   Fig 3: Connecting Rod Cap & Nuts

   Courtesy of GENERAL MOTORS CORP.
6. On the edge of the gaging plastic envelope there is a graduated scale. Without removing the gaging plastic, measure the compressed width at the widest point.

   If the flattened gaging plastic tapers toward the middle or the ends, there may be a difference in clearance indicating taper, low spot or other irregularity of the crankshaft bearing or the crankpin journal.

7. Normally the crankpin journals wear evenly and are not out-of-round. However, if a connecting rod bearing is being fitted to an out-of-round 0.0254 mm (0.001 in maximum) crankpin journal, be sure to fit to the maximum diameter of the crankpin journal. If the connecting rod bearing is fitted to the minimum diameter and the crankpin journal is excessively out-of-round, the interference between the connecting rod bearing and the crankpin journal will result in rapid connecting rod bearing failure.
   Fig 4: Measuring Crankpin Journals

   Courtesy of GENERAL MOTORS CORP.
8. Compare the connecting rod bearing clearance to the specifications. Refer to Engine Mechanical Specifications .
9. If the connecting rod bearing clearances exceed specifications, replace components as required.
10. Remove the flattened gaging plastic.
11. Measure the remaining crankpin journals.