TM 9-2320-260-34-1
3-51. CYLINDER HEAD REPAIR (Contd)
NOTE
Operating instructions are provided with vacuum tester.
16.
Vacuum test intake and exhaust valves (2) for proper valve seating.
NOTE
Valves and valve seats must be dry.
Use correct size vacuum cup when testing valves.
Hold vacuum cup over head of valve (2), and seat flat on cylinder head surface (1) surrounding
17.
valve.
Turn tester shutoff valve to open position and hold push button down until indicator hand on
18.
vacuum gage stops climbing between 18-25 in. (457-635 mm) of mercury (Hg).
Close tester shutoff valve and release push button.
19.
20.
Begin timing indicator hand at 18 in. (457 mm) of mercury (Hg) on vacuum gage. Stop timing
indicator hand at 8 in. (203 mm) of mercury (Hg). Valve (2) seating is satisfactory if timing is longer
than 10 seconds.
Tap stem and end of valves (2) with soft-head hammer if time is less than 10 seconds. Retest by
21.
repeating steps 16 through 20.
Inspect for loose connections and leakage in vacuum hose if valve (2) seating is still unsatisfactory.
22.
Tighten any loose connections on vacuum hose and repeat steps 16 through 20.
23.
24.
Regrind valves before retesting if test fails (para. 3-77).
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