Toyota Supra 1990 Manual page 78

EM-46 ENGINE MECHANICAL - Cylinder Head
EM0373
EM3026
EM0185
EM0186
(e) Check the surface of the valve stem tip for wear.
If the valve stem tip is worn, regrind it with grinder or
replace the valve if necessary.
NOTICE: Do not grind off more than minimum overall
length (See page EM-45'.
12.
INSPECT AND CLEAN VALVE SEATS
(a) Using a 45° cutter, resurface the valve seats. Remove
only enough metal to clean the seats.
(b) Check the valve seating position.
Apply a thin coat of prussian blue (or white lead) to
the valve face. Install the valve. Lightly press the valve
against the seat. Do not rotate the valve.
(c) Check the valve face and seat for the following:
• If blue appears 360° around the face, the valve is
concentric. If not, replace the valve.
• If blue appears 360° around the valve seat, the
guide and seat are concentric. If not, resurface the
seat.
• Check that the seat contact is on the middle of the
valve face with the following width:
1.0 - 1.4
mm
(0.039 - 0.055
in.)
If not, correct the valve seat as follows:
• If seating is too high on the valve face use 30° and
45° cutters to correct the seat.
• If seating is too low on the valve face, use 60° and
45
°
cutters to correct the seat.