Cylinder Block/Main Bearing Caps

Cylinder Block/Main Bearing Caps:

The new M73 cylinder block and main bearing caps are similar to the M70 engine. The cylinder block casting is designed to mate with the A5S 560Z transmission.

Like the M70, the M73 cylinder block is cast from an aluminum/silicon alloy called Alusil. During the casting process high concentrations of silicon crystals are introduced and maintained in the cylinder walls of each cylinder bore.

A special machining, honing and etching process produces a wear resistant, silicone crystal impregnated cylinder wall that eliminates the need for cylinder liners and assures a long cylinder block life.

The #7 main bearing support has been modified for use of semi-circular discs (like M60) in place of the thrust bearing used in the M70.


Cylinder Block Key Specifications:

- Block configuration - 60° V12
- Bore = 85mm
- 91 mm Bore to Bore (center) measurement

Main Bearing Cap:

The main bearing cap design is identical to the M70 configuration. Each main bearing cap is torqued to the block with four bolts. Two are tightened to the vertical axis of the crankshaft and the other two at an opposed 60° angle (parallel to piston travel).

This two directional mounting of the bearing cap promotes bottom end stability and added torsional strength.




A new piston oil cooling nozzle is fitted directly into the main bearing support area of the block which accesses the main oil pressure supply. The steady oil stream from the nozzle continuously cools the underside of the piston.

The nozzle is threaded and screws into the cylinder block with a 4mm allen wrench.