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 TM 55-1905-223-24-5
(s)
If the marks are not broken, check the adjustment of the facing machine
and the condition of the grinding wheel.
(t)
Valves and valve seats that are correctly machined do not require the
use of lapping compound to make an airtight seal. If the Valve Seating
Test shows leakage, you can use a small amount of lapping compound on
the valve and seat to make an airtight seal.
(u)
The correct conditions on the valve and valve seats are:
1
No marks or scratches on the valve face or valve seat.
2
No marks or scratches in the valve guide.
3
The angle of the valve face must be exactly 30 degrees.
4
Valve guide to valve stem clearance must be a minimum of 0.0022
inch (0.056 mm).
g.
Valve Springs. Inspection and replacement.
NOTE
Weak valve springs can cause wear and damage to the valve and valve seat.
Weak springs can also change the valve timing and cause the valve to hit the
top of the piston.
(1)
Use the valve spring tester to test valve spring.
(2)
Compress the spring to the working force shown in Table 4-2.
(3)
Check the amount of force required to compress the spring, if not within
limits discard the spring.
(4)
Use spacers under the valve spring when the valve and valve seat have had
a total of 0.030 inch (0.76 mm) material removed. Do not use more than
two spacers under a valve spring.
(5)
Replace any springs which do not meet the specifications in Table 4-2.
See other spring specifications in Table 4-5 at the end of the repair
procedures.
Table 4-2. Valve Spring Data -- inch (mm) lb (N)
Approximate Working Force to Compress
Free Length - in (mm)
Length - in (mm)
Minimum - lb (N)
Maximum - lb (N)
2.685
1.724
147.25
162.75
(68.20)
43.79)
(655)
(724)
4-19
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