side” of the primary chain, necessitating the double-
flexure type chain.
The chain is controlled by three fixed chain guides
and a pivoting tensioner arm (Fig. 112). These guides
utilize low-friction and long wearing nylon plastic
wear faces. To tension the primary chain, a fully
automatic spring-loaded, engine oil-fed, hydraulic
tensioner is used. The tensioner is mounted in the
right cylinder head with the plunger contacting the
pivoting tensioner arm. A mechanical ratchet mecha-
nism inside the tensioner prevents excessive chain
slack upon engine start-up as the chain wears. The
tensioner is designed with an internal oil reservoir to
assure noise-free performance, even during engine
start-up before oil pressure reaches the tensioner.
For lubrication the primary chain utilizes oil leak-
age from the front of the oil pump. This oil spills on
the crankshaft sprocket, which is then carried by the
chain throughout the primary drive.
The secondary timing chain drive system uses
two conventional roller-type chains, one at each cyl-
inder bank (Fig. 20). The purpose of the secondary
chain is to provide a mechanical driven connection
between the intake and exhaust camshafts. The
intake camshafts drive the exhaust camshafts. The
sprockets for both intake and exhaust camshafts are
a press-fit and are only serviced as an assembly with
the camshafts.
To tension the secondary chain a spring-loaded,
hydraulic tensioner is used at each bank and
attaches to each cylinder head between the intake
and exhaust camshafts (Fig. 20). The tensioner incor-
porates upper and lower chain guide faces. The lower
guide face is attached directly to the tensioner’s
hydraulic plunger. Also, the tensioner uses an inter-
nal oil reservoir design to prevent engine start-up
noise. The secondary chains are lubricated via an oil
passage through the upper guide face on each ten-
sioner.
Fig. 112 TIMING DRIVE SYSTEM
1 – CAMSHAFT DAMPER (IF EQUIPPED) 7 – CHAIN GUIDE
2 – CHAIN GUIDE 8 – CHAIN TENSIONER ARM
3 – ACCESS PLUG 9 – CHAIN TENSIONER
4 – CAMSHAFT POSITION SENSOR 10 – CAMSHAFT SPROCKETS
5 – PRIMARY TIMING CHAIN 11 – CHAIN GUIDE
6 – CRANKSHAFT SPROCKET
LH ENGINE 2.7L 9 - 77
VALVE TIMING (Continued)
To Next Page
Loading...
