Timing Chain Tensioner: Description and Operation

35 Cylinder heed
75 Closing plug
76 Sealing ring
77 Compression spring
78 Detent spring
79 Pressure bolt
83 Chain tensioner housing
84 Gasket
85 Tensioning rail

a Throttle bore 1.5 mm dia.
b Throttle bore 1.3 mm dia.

NOTE: This engine is provided with a hydraulic detent chain tensioner without valve.

The pressure required for tensioning timing chain comprises the force of the compression spring (77) and the oil pressure in chain tensioner, independence of engine oil pressure.

In the event of shock-type loads, a throttle bore (a) of 1.5 mm dia. in oil feed and a throttle bore (b) of 1.3 mm dia. in thrust bolt prevents fast flowing-off of oil.

The chain tensioner housing (83) holds a detent and on pressure bolt (79) a detent spring (78).

The pressure bolt moves forward from detent to detent in accordance with elongation of chain. Travel to the rear is limited by detents. As a result, the pressure bolt cannot be pushed back when the engine is stopped. Any lumping of the loose timing chain or any chain noise when the engine is started is therefore eliminated.

The oil required for operation of chain tensioner is provided via first camshaft bearing, the cylinder head bolt bore at front right and a transverse duct in cylinder head.