Valve Seats - Honda Acura NSX 1991 Service Manual

Valve Seats

Renew the valve seats in the cylinder head using a
1 .
valve seat grinder.
NOTE: If guides are worn (page 6-431,
(page 6-44) before grinding the valve seats.
Carefully grind a 45O seat, removing only enough
2.
material to ensure a smooth and concentric seat.
3. Bevel the upper edge of the seat with the 30° stone
and the lower edge of the seat with the 60° stone.
Check width of seat and adjust accordingly.
4. Make one more very light pass with the 45O stone
to remove any possible burrs caused by the other
stones.
Valve seat Width:
Standard: IN 0.80- 1 .OO mm (0.031-0.039 in)
EX 1.25-1.55 mm (0.049-0.061 in.)
Service Limit: IN 1.5 mm (0.059 in)
EX 2.0 mm (0.079 in)
Seat Width
6-42
5 . After resurfacing the seat, inspect for even valve
seating: Apply Prussian Blue compound to the valve
face, and insert valve in original location in the head,
then lift it and snap it closed against the seat sever-
replace them
al times.
ACTUAL
VALVE
SEAT
PRUSSIAN BLUE COMPOUND
6. The actual valve seating surface, as shown by the
blue compound, should be centered on the seat.
l
must make a second cut with the 60° stone to
move it down, then one more cut with the 45O
stone to restore seat width.
l If it is too low (closer to the valve edge), you must
make a second cut with the 30' stone to move
it up, then one more cut with the 45O stone to
restore
NOTE: The final cut should always be made with
the 45O stone.
7. Insert intake and exhaust valves in the head and
measure valve stem installed height.
Valve Stem Installed Height (IN and EX):
Standard (New):
Service
60"
8. If valve stem installed height is over the service limit,
replace valve and recheck. If still over the service
limit, replace cylinder head; the valve seat in the head
is too deep.
Y
If it is too high (closer to the valve stem), you
seat width.
41.55-42.35 mm
Limit: mm (1.6707 in)
42.435
INSTALLED HEIGHT