has an orifice to restrict the oil flow to the rocker
arms. The rear rocker arm bracket also has an O-ring
that seals against the head bolt. This seal prevents oil
from going down around the head bolt and leaking
past the head gasket or spacer plate gasket. The O-
ring must be replaced each time the head bolt is
removed from the rear rocker arm bracket.
Holes in the rocker arm shafts let the oil give
lubrication to the valve system components in the
After the lubrication oil has done its work, it goes
back to the engine oil pan.
There is a bypass valve in the oil pump. This
bypass valve controls the pressure of the oil coming
from the oil pump. The oil pump can put more oil into
the system than is needed. When there is more oil
than needed, the oil pressure increases and the by-
pass valve will open. This allows the oil that is not
needed to go back to the engine oil pan.
With the engine cold (starting conditions), bypass
valves (9 and 10) will open and give immediate lubri-
cation to all components when cold oil with high
viscosity causes a restriction to the oil flow through
oil cooler (15) and oil filter (11). Oil pump (13) sends
the cold oil through the bypass valves around the oil
cooler and oil filter to oil manifold (5) in the cylinder
When the oil gets warm, the pressure difference in
the bypass valves decreases and the bypass valves
close. Now there is a normal flow of oil through the
oil cooler and oil filter.
The bypass valves will also open when there is a
restriction in the oil cooler or oil filter. This action
does not let an oil cooler or oil filter with a restriction
prevent lubrication of the engine.
ROCKER ARM OIL SUPPLY
FLOW OF OIL (ENGINE COLD)
9. Oil cooler bypeee. 10. Oil filter bypasa. 11. Oil filter. 12. Turbocharger. 13. Oil pump. 14. Oil pan. 15. Engine oil cooler.