Reaming Valve Guide; Valve Seat And Face Angles; Valve Seat After Grinding With Flat Stone - Pontiac Grand Prix Service Manual

V-8
ENGINE
6-53
I
A-SEAT WIDTH
6-FACE ANGLE
C-SEAT ANGLE
D-VALVE FACE
D
Tv
A
Fig. 6-91 Valve Seat and Face Angles
4. Clean valve guides thoroughly, using valve guide
cleaner J 8 10 1 (Fig. 6-90).
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.
7. Clean push rods and thoroughly clean out oil passage
through center of rod. Inspect to see that the rod is
straight.
8. Clean rocker arms and rocker arm balls, and
visually inspect for evidence of wear.
9. Clean spark plugs as outlined in ELECTRI-
CAL SECTION.
10. Clean and inspect valve lifters.
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" on all large valve heads, 45" on
all small valve heads and exhaust valve seat
angle is 4 5 O on all cylinder heads. Intake valve
face angle is 29" on large valves, 440 on small
valves and exhaust valve face angle is
4 4
on all
valves. This will provide hairline contact between
valve and seat to provide positive sealing and
reduce build-up of deposits on seating surfaces
(Fig. 6-91).
GRIND WITH FLAT STONE
J
rv
SEAT
WIDTH
Fig. 6-92 Valve Seat After Grinding with Flat Stone
NOTE: Some early production small valve heads
will still have 30" angle seats.
DO NOT USE REFACING EQUIPMENT
EXCESSIVELY; only enough material should be
removed to true up surfaces and remove pits. The
valve head will run hotter as its thickness is
diminished; therefore, if 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 it is neces-
sary 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 fit).
Width of exhaust valve seats should be 1/16"
(.048":.070"). Intake valve seat should be be-
tween 3/64" and 1/16" (.045"-.07lU). If seat
width is excessive, it should be narrowed by
grinding with a flat stone (Fig. 6-92). This is the
only method that should be used to narrow the
seat.
NOTE: Lapping of valve seats is not required or
recommended.
Fig. 6-93 Reaming Valve Guide