Cup number ST-1 257-38 is used for testing both intake and exhaust valves. Use seal ST-1
257-36 for testing exhaust valves, and seal ST-1 257-37 for testing intake valves.
(a) Install the cup on the vacuum hose, coat the seal with petrolatum, VV-P-236, and install it in the cup.
(b) Place the cup on a dean, flat piece of plate glass, turn on the pump, and open the shutoff valve.
(c) When the vacuum gage reaches 1 8 to 25 inches Hg (60.8 to 84.4 kPa), dose the shutoff valve to
isolate the gage, hoses, and cup.
(d) If vacuum will not reach 18 to 25 inches Hg (60.8 to 84.4 kPa), or the gage drops after dosing the
shutoff valve, leakage in the hoses or fittings is indicated. Repair leaks before combing the test
Coat the seal with petrolatum VV-P-236, and place the cup over the valve so that the seal rests on the
head surface (Figure 9-11).
Operate the vacuum pump to pull a vacuum of 18 to 25 inches Hg (60.8 to 84.4 kPa) over the head of the
Close the shutoff valve, and time the vacuum drop from 18 to 8 inches Hg (60.8 kPa to 27.0 kPa).
If the elapsed time is less than 10 seconds, leakage is indicated. To be sure the valve is seated, tap the
stem and of the valve with a soft, light hammer and retest.
If leakage is still indicated, remove the cup, and seal the outer edge of the valve seat insert and cylinder
head joint with grease. Repeat the vacuum test (timing will not be necessary).
Remove the cup and examine the grease seal. If breaks in the grease seal are found, leakage is indicated
between the valve seat insert and the cylinder head counterbore. Re-stake or replace the valve seat insert
in accordance with paragraph 9-11.
If the grease seal is intact, leakage at the valve seat is indicated.
Lap the valve and seat lightly using lapping compound SS-L-1 682, and repeat the timed vacuum test. If
leak down still occurs in under 10 seconds, a complete check of reseating equipment and operating
procedures should be made; a properly finished seat will hold vacuum for 10 seconds or more.
Preservation. If assembled head is to be stored, spray all surfaces with preservative oil MIL-L-21260. While
spraying, lift each valve slightly to be sure preservative oil penetrates to the seat area
9-10. CYLINDER HEAD ASSEMBLES INSTALLATION. Install the cylinder heads as follows (see Figure 9-1, Figure 9-
2, and Figure 9-12):
Compressed air used for cleaning or drying can create airborne particles that may enter the
eyes. Pressure shall not exceed 30 psi (207 kPa). Wearing of goggles Is required to avoid
Injury to personnel.
To avoid cylinder head leakage, clean all traces of old gaskets and carbon from the cylinder
head and cylinder block gasket surfaces. During cleaning, plug all holes In the cylinder block
to prevent entrance of dirt. Be especially careful that dirt does not block the orifice In the oil
restrictor expansion plug. To avoid false torque readings, clean all capscrews and threaded
holes using thread chasers, taps and dies, and compressed air as necessary.
Place a new cylinder head gasket (13, Figure 9-1) over the dowel pins in the cylinder block The word TOP must
be visible when the gasket is in the installed position.
Install four new water seal grommets (14), three new push rod tube grommets (15), one new oil seal grommet
(16), and one new cylinder head capscrew grommet (17) in the cylinder head gasket (13).