Engine Overhaul: Valves, Valve Springs, and Guides Inspection
ENGINE
OVERHAUL
7
Valves, valve springs and guides - inspection
Valves
NOTE: Two types of exhaust valve may be
fitted - standard valves A in illustration or
carbon break valves - B in illustration.
Carbon break valves may be identified by the
machined profile C on the valve stem. To prevent
exhaust valves sticking, standard exhaust valves
should be replaced with carbon break valves
during engine overhaul.
NOTE: Modified inlet valves, carbon break
exhaust valves and valve guides are fitted
to later engines. The modified exhaust
valves may be identified by measuring the
distance A from the valve head face to the top of
the undercut on the valve stem. Additionally, the
exhaust valves have a black nitrided finish whilst
the inlet valves have a chrome finish.
Early valves - dimension A = 29.5 to 30.5 mm (1.16
to 1.20 in)
Later valves - dimension A = 32.5 to 33.5 mm (1.28
to 1.32 in)
The modified valves may be fitted to early engines in
engine sets provided that the modified valve guides
are also fitted.
Valve guides
NOTE: The modified valve guides fitted to
later engines are 5 mm (0.211 in) shorter
than the early type guides, the overall
length of the modified guide being 57 mm (2.24
in); the reduction in length being the distance
the guide protrudes into the combustion
chamber side of the cylinder head. The modified
guides may be fitted to early engines in engine
sets provided that the modified inlet and carbon
break exhaust valves are also fitted.