Pontiac tempest 1968 Service Manual page 269

6-52
1968 P O N T I A C SERVICE MANUAL
w i l l permit o i l to be pulled Into the combustion
chamber, causing fouled spark plugs and clogged
piston rings. Oil deposited on valve heads w i l l
carbonize and burn, causing valves • to leak with
resultant loss of engine power. Therefore, valves
must operate properly and If Inspection discloses
any malfunction of valves, the trouble must be cor­
rected to avoid future damage to valves or related
engine parts.
1. Inspect valves and seats to determine condition
before cleaning. Also water passage plugs for evi­
dence of leakage.
2. Clean valves thoroughly to remove deposits
from head and stem.
3. Clean and Inspect cylinder head as follows:
a. Clean carbon deposits from combustion
chambers and a l l sludge or foreign matter from
other' areas of cylinder head. If a scraper or wire
brush is used for cleaning, use care to prevent
damage to valve seats.
CAUTION; To prevent damage to valve seat it is
good practice to keep wire brush well away from
seat.
b. - Clean cylinder head thoroughly, using suit­
able cleaning equipment.
4. Clean valve guides thoroughly, using valve guide
cleaner J 8101 (Fig. 6-89).
5. Visually inspect valve guides for evidence of
wear, especially the end toward the spring seat. If
a guide is scored or galled, Install valve with
proper oversize stem according to procedure.
6. Clean valve springs and inspect to see that
they meet specifications.
J-8101
/
7. Clean push rods and thoroughly clean out o i l
passage through center of rod. Inspect to see that
the rod is straight.
8. Clean rocker arms and rocker a r m balls, and
visually inspect for evidence of wear.
9. Clean spark plugs as outlined in ELECTRICAL
SECTION.
10. Clean and inspect valve l i f t e r s .
VALVES AND SEATS-RECONDITION
1. Reface valves and seats as follows:
Valves should be ground on a special bench grinder
designed specifically for this purpose and built by a
reputable manufacturer. Valve seats should be
ground with reputable power grinding equipment
having stones of the correct seat angle and a suitable
pilot which pilots in the valve stem guide. To ensure
positive sealing of the valve face to its seat, the
grinding stones should be carefully refaced before
any grinding is done. Intake valve seat angle is 30°,
exhaust valve seat angle is 4 5 ° . Intake valve face
angle is 29° and exhaust valve face angle is 4 4 ° .
This w i l l provide hairline contact between valve and
seat to provide positive sealing and reduce build-up
of deposits on seating surfaces (Fig. 6-90).
DO NOT USE RE FACING EQUIPMENT EXCES­
SIVELY; only enough material should be removed
to true up surfaces and remove p i t s . The valve head
w i l l run hotter as its thickness is diminished; there­
fore, i f valve face cannot be cleaned up without
grinding to point where outside diameter of valve
has a sharp edge, the valve should be replaced.
Whenever i t is necessary to replace a valve, the
new valve should be of the same stem diameter as
the valve removed (unless the valve guide is reamed
to provide proper f i t ) .
Width of exhaust valve seats should be 1/16"
(.048"-.070 TT ). Intake valve seat should be between
3/64" and 1/16" (.045"-.071"). If seat width is
excessive i t should be narrowed by grinding with a
A—SEAT
W I D T H
F i g . 6-89 Cleaning Valve G u i d e F i g . 6-90 V a l v e Sear and Face Angles