Jeep UNIVERSAL CJ-2A - Page 41

D
L4-134 ENGINE
NOTE: When using a spring checking fixture as
shown in Fig. 46, it is necessary to convert the
torque wrench reading which is in pounds-feet to
the static pound pressure specified above according
to the instructions furnished with the wrench. For
example; should the torque wrench reading be
50 lb-ft. and the wrench is two feet long the static
pressure of the spring will be 50 x 2 or 100 lbs.
Clean the valve guides with a standard valve guide
cleaner or a wire brush. Check the valve guides in
the cylinder block. Replace valve guides which are
broken or worn enough to cause excessive valve
'Stem-to-guide clearance. See Par. D-58.
Standard intake valve clearance is .0015 to .00325"
[0,038
a 0,083 mm.} and the exhaust valve clearance
is .0025" to .0045" [0,0635 a 0,1143 mm.]. Excessive
clearance between the valve stems and guides will
cause improper seating and burned valves. When
there is a. tendency to draw oil vapor through the
guide causing excessive oil consumption, fouled
spark plugs, and poor low-speed performance. To
check the clearance of the valve stem to the valve
guide, take a new valve and place. in each valve
guide. Check the clearance with a sUltably mounted
dial indicator or feel the clearance by moving the
valve stem back and forth. If this check shows
excessive clearance it will be necessary to replace
the valve guide.
D-55. Refacing Valves ,
Reface the valves with a valve refacer. The valve
refacer manufacturer's instructions should be fol-
FIG. 47-GAUGING VALVE SEATS
lowed carefully to ensure a valve face concentric
with the valve stem. Reface both intake and ex-
haust val_ves to an angle of 45 o. Take off only the
minimum of metal required to clean up the valve
faces.
r If the thickness of the edge of the valve head is
reduced to less than~" [0,8 mm.] replace the valve.
NOTE: Cocked or deformed valve springs or
improperly installed or missing locks, can be
responsible for valve problems.
40
FIG. 48-REFACING VALVES
1-Valve Refacer
2-Valve
D-56. Valve Seat Inspection and Refacing
Inspect the valve seats for cracks, burns, pitting,
ridges, or improper angle. During any general
engine overhaul it is advisable to reface the valve
seats regardless of their condition. If valve guides
are to be replaced, this must be done before refac-
ing the valve seats. Note that later engines have
hardened exhaust valve seat inserts.
When necessary to reface the valve seats, use a
valve seat grinder in accordance with the grinder
manufacturer's instructions. Any grinding of valve
seats should be preceded by touching up the
grinding stone so that their angles are accurate and
the stone is not clogged. Grind each valve seat to
a true 45° angle. Never grind any more than is
necessary to clean up pits, grooves, or to correct
the valve seat runout. Check the valve seats with
a dial indicator as shown in Fig. 47 after refacing.
The valve seat should not be out of round more
than .002" [0,051 mm.]. A simple check can be
made in the absence of a dial indicator by spreading
a thin coat of pencil lead or bearing-fitting blue on
the valve face and then inserting the valve into
the valve seat. With hand pressure, rotate the valve
a quarter turn and then remove the valve and ob-
serve the transfer of blue (or pencil lead) to the
valve seat. An uneven transfer will indicate an
inaccurate valve and valve seat refacing operation.
After the seat is ground, check its width with a
seat width scale or a steel scale placed across the
face of the seat. The valve seat width after refacing
should measure %2" [2,3 mm.] and not wider than
Ys" [3,2 mm.]. Valve seat width is vital. Too wide
a seat can cause seat burning as it tends to trap
and hold carbon particles. Seats that are too narrow
will not transfer heat to the coolant rapidly enough
to keep the valves in proper operating condition.
When a valve seat has been refaced several times
or where it must be cut deeply for adequate recon-
ditioning, the seat may become too wide for efficient
operation. Narrow the seat without changing its
position in relation to the valve face by using a
valve seat relief counterbore above the seat and a
valve seat narrowing cutter below the seat. These
operations are performed only after the valve seats