Connecting Rod: Description and Operation

DESCRIPTION





CAUTION: If the connecting rod bolts are ever loosened, replace all of the connecting rods.

NOTE: Slight bluing or heat transfer witness marks around the connecting rod caps and crankshaft journal is normal. This is part of the heat treating process from the factory and Does Not indicate premature bearing failure.

The pistons are of a free floating design. Circlips secure a full floating piston pin. The piston pin is offset 0.4 mm (0.016 in) toward the piston's major thrust surface to reduce slap. The pistons have a phosphated surface treatment and the piston skirts have a graphite treatment for scuff resistance. The piston skirts have notches to provide the necessary clearance for the oil jets when the pistons are at BDC. Oil jets in the engine block lubricate and cool the piston and pin assembly.


The connecting rods are made of forged steel. The rods have a trapezoidal small end and a diagonally cracked (fracture-split) rod cap. The fracture-split rod cap creates a unique mating surface, which produces a tight fit and strong resistance to lateral movement. The trapezoidal small end allows for clearance between the piston head and the connecting rod and provides increased load capability by increasing the surface area on both load sides of the wrist pin. The connecting rods are induction hardened, which produces a blue discoloration on the rod surface. This discoloration is not a sign of overheating.


WARNING: The connecting rods are not serviceable, and must be replaced every time the bolts are removed. Otherwise, the precision fit is no longer achieved.





Piston numbers are etched on the piston crown for cylinder bank identification. Left cylinder bank pistons are identified as numbers four through six. Right cylinder bank pistons are identified as numbers one through three. An orientation arrow points toward the front of the engine.


The pistons are made of a high strength aluminum alloy and have an oval shape to reduce friction and noise. The piston crown consists of a combustion bowl and four recesses machined for the valves.