Cylinder Block Components (page 3 of 10)

ENGINE - V8

12-2-4

DESCRIPTION AND OPERATION

Crankcase Ventilation
The crankcase ventilation system is pressure regulated by a valve mounted at the rear of the inlet manifold. Vacuum 
supply ports are incorporated on the valve for the power brake booster and the fuel pressure regulator

The pressure regulating vent valve varies the vacuum applied to the crankcase depending on engine load. The valve 
is balanced between spring pressure and the amount of manifold vacuum. At idle when the vacuum is high, the valve 
closes down and only allows a small amount of blow-by vapours to pass into the manifold. At part to full load 
conditions, the spring opens the valve and additional blow-by gasses flow into the manifold. An additional tube leads 
the blow-by gasses through the manifold and up to the mixing plate.

The crankcase ventilation system is completely sealed. Hose clamps are used at all connections to ensure that the 
system does not contain any leaks.

The crankcase ventilation system uses a cyclone separator to purge the blow-by gasses of any oil vapours. The oil 
vapours condense in the separator and drain back into the sump.

Crankcase Ventilation System

1 Oil separator
2 Breather hose, oil separator to vent valve
3 Breather hose, LH camshaft cover to oil 

separator

4 Inlet manifold cover and vent valve
5 Inlet manifold
6 Oil drain pipe assembly

7 Inlet manifold vacuum pipe
8 Mixing plate
9 Vent valve spring

10 Vent valve diaphragm
11 Atmospheric vent
12 Blow-by gasses

M12 7839A

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