International Harvester Company Cub Lo-Boy C-60 Service Manual page 28

to clear away grinding dust. Grind the
seat sufficiently to provide an even,
smooth surface.
Dress the stone to the correct angle.
Lightly lubricate and install the pilot of the
correct size into the valve guide bore.
Lower the grinder head over the pilot
shank until the stone just clears the valve
seat. Turn on the power and very gently
allow the stone to contact the valve seat.
Very little pressure other than the normal
weight of the stone should be used. Sudden
hard pressure can cause cocking of the
pilot in the guide and result in eccentric
grinding. Raise the stone freq4ently from
the valve seat to prevent overheating and
Check the seat concentricity, roundness
and valve face contact using Prussian
blue. Spread an extremely thin film of
this blue on the valve face and insert the
valve into its guide. With pressure on the
exact center of the valve head, make a
quarter turn rotation in the seat. Remove
the valve and inspect the impression made
upon the seat by the transfer of blueing,
and upon the valve face by the removal of
blueing. Check several times to guarantee
that no error was made. If a full seat-
width contact around the entire circle of
seated valve is not shown, the angles do
not match. It will then be necessary to re-
dress the valve seat grinding stones,
changing the angle sufficiently to correct
the error. The correction should be made
on the valve seat, and not on the valve.
Correct Seat
The location of the area of contact between
the valve and the seat is a very important
factor in securing maximum valve life.
Seating the valve with the sharp edge of the
seat not contacting the valve face is un-
desirable. This sharp edge tends to break
off face deposits which may lead to valve
failure.
Seat too wide
Similarly, the location of the upper line of
contact well below the top of the valve face,
is also undesirable because a large over-
hang prevents rapid cooling of the outer
edge of the valve.
Seat too narrow
FESM-32SS
After grinding the seats it may be found
that the seats are considerably wider than
the specified width of 3/64 inch. Valve
seats that are too wide may be narrowed
by grinding down the top edge of the seat
with a stone mounted on the grinder head.
The stone must be a smaller angle than
0
the valve seat (15 preferably).
FEA-63042
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