Pistons And Connecting Rods

The connecting rods are manufactured from forged steel and have fracture split connecting rod bearing caps to make sure precision re-assembly for bearing alignment. The connecting rod bearing caps are not selectable. Adjustment for large end bearing journal size is made by selecting the correct large end bearings after measuring the crankshaft journals.

There are a number of grades of large end bearing available. Each size of the bearings is color coded and inkjet marked with a letter on the running face of the bearing. The crankshaft is laser etched with a string of four alpha characters in the order of crankshaft journals 1-4 and a data matrix code containing the same data. The correct large end bearings are selected with reference to a selection chart in order to achieve optimum running clearances.

For additional information, refer to: SPECIFICATIONS 

There is only one grade of piston diameter. The pistons are marked to ensure correct assembly, with the marks facing the front of the engine. The top face of the piston has an arrow that must also point towards the front of the engine. The piston crown has a recess for optimization of the fuel/air mixture and combustion.

A three ring piston sealing system is used. An oil control ring is located in the lower groove. Two compression piston rings are located above the oil control ring. The piston ring gaps must be positioned at 120 degrees to each other.

The pistons are cooled with engine oil from four piston cooling oil jets installed in the cylinder block.

The pistons are attached to the connecting rods with a gudgeon pin which is secured with two circlips.

The gudgeon pin is located through the small end bearing in the connecting rod which allows the piston to articulate with the linear movement of the connecting rod. The circlips locate in grooves in the piston.