V8 Engine: Description and Operation for 35, 39, and 42 Models
ENGINE
8
DESCRIPTION AND OPERATION
Distributor drive and timing chain lubrication
1. Bearing
2. Camshaft
3. Key
4. Camshaft timing chain sprocket
5. Spacer
6. Distributor drive gear
The distributor drive and timing chain are lubricated
from the camshaft front bearing. The feed to the
timing chain is channelled along the camshaft
sprocket, key and spacer.
Hydraulic tappets
1. Clip
2. Pushrod seat
3. Inner sleeve
4. Upper chamber
5. Non-return ball valve
6. Spring
7. Outer sleeve
8. Lower chamber - high pressure
The purpose of the hydraulic tappet is to provide
maintenance free and quiet operation of the inlet
and exhaust valves. It achieves this by utilising
engine oil pressure to eliminate the mechanical
clearance between the rockers and the valve stems.
During normal operation, engine oil pressure present
in the upper chamber passes through the non-return
ball valve and into the lower, high pressure,
chamber.
When the cam begins to lift the outer sleeve, the
resistance of the valve spring felt through the push
rod and seat causes the tappet inner sleeve to move
downwards inside the outer sleeve. This downward
movement of the inner sleeve closes the ball valve
and increases the pressure in the lower, high
pressure chamber, sufficiently to ensure that the
push rod opens the valve fully.
As the tappet moves off the peak of the cam the ball
valve opens to equalise the pressure in both
chambers which ensures the valve closes when the
tappet is on the back of the cam.
