Crankshaft and Connecting Rods

Connecting Rod Inspection


This Inspection was done to check if con-rods had any bends or twists. If they were bent or twisted this would cause damage to the cylinder bore causing scoring of the pistons or the cylinders themselves as I explained in a earlier post.

This was done using a connecting rod aligner and a feeler gauge. Connecting Rod was aligned using this so that accurate angles of bend or the amount of twist can be measured with the feeler gauge.

the tested con-rods did have some bend and twist in them The worst one had a Bend of 0.70mm and a twist of 0.63mm. This can be rectified using a hydraulic rod straitening press to bend rods to the correct alignment.

Crankshaft Inspection 

Measurements Taken:

• Bearing Journals
• Main Journals
• Big end Journals
• Crankshaft Deflection

What I was looking for

The main inspection is done on the crankshaft journals using a micrometer to check for the amount of taper and out-of-round. 

Out-of-round is caused during cold starting because there is little or no lubrication in these areas when the engine is first started and if the engine is revved excessively extra ware occurs. 

Tapered ware is caused by the piston con-rods being misaligned causing the bearings to not ware uniformly this also causes ware on piston skirts in turn wearing out the cylinder bore.

This done using the micrometer to check how much the bearing has worn down in 2 areas of the bearing which are horizontally and vertically this measurement should be no more than 0.05 mm away from the manufacturers specification.