Chevrolet 1963 Corvette, Руководство по ремонту и настройке, Страница: 115 / 346

108 ENGINE AND ENGINE REBUILDING
Checking valve seat concentricity with run-out
gauge
LAPPING THE VALVES
When valve faces and seats have been re-faced
and re-cut, or if they are determined to be in
good condition, the valves must be "lapped
in" to ensure efficient sealing when the valve
closes against the seat.
1. Invert the cylinder head so that the
combustion chambers are facing up.
2. Lightly lubricate the valve stems with
clean oil, and coat the valve seats with valve
grinding compound. Install the valves in the
head as numbered.
3. Attach the suction cup of a valve lap
ping tool to a valve head. Moisten the suction
cup to securely attach the tool to the valve.
4. Rotate the tool between the palms,
changing position and lifting the tool often to
prevent grooving. Lap the valve until a
Lapping the valve and seat by hand—typical
smooth, polished seat is evident (you may have
to add a bit more compound after some lap-
ping is done).
5. Remove the valve and tool, and remove
ALL traces of grinding compound with sol-
vent-soaked rag, or rinse the head with sol-
vent.
NOTE: Valve lapping can also be done by
fastening a suction cup to a piece of drill
rod in a hand "eggbeater" type drill. Pro-
ceed as above, using the drill as a lapping
tool. Due to the higher speeds involved
when using the hand drill, care must be
exercised to avoid grooving the seat. Lift
the tool and change direction of rotation
often.
Valve Springs and Seals
Small-block engines use only one type of valve
stem oil seal. The small-block seal is simply
an O-ring which is installed on the lower
groove of the valve stem and seals against the
lower inside portion of the valve spring re-
tainer.
Big-block engines have used four types of
seals over the years. The first type is a rubber
"umbrella" seal which is installed on the valve
guide boss of the cylinder head and wipes the
valve stem as the valve moves within the seal.
The second type of seal is a nylon "umbrella"
seal which is integral with the valve spring
retainer. The third type is also nylon and is
integral with the spring retainer, but,is no
longer serviced. If defective, the third type
must be replaced with the second type. Both
the second and third types seal against the
top of the valve stem and divert any oil which
may seep through. The fourth type is of the
HAND
DRILL
SUCTION
Fabricated valve lapping tool