Figure 4-5. Narrowing valve seat. - TM-5-4320-258-340042

TM 5-4320-258-34

Length

Load (minimum)

valve is installed in the guide from which it was

1-45 / 64 inches (closed)

42 pounds

removed.

1-27 / 64 inches (open)

86 pounds

(3) With the engine stopped, temporarily

set the intake-valve-to-tappet clearance to 0.014 inch

(9) Grind the valve seats. The seat angle

and the exhaust valve-to-tappet clearance to 0.017 inch

of the intake valves is 30. The seat angle of the

(cold).

exhaust valve is 45. Use a dial indicator to check the

(4) Install the cylinder head (para 4-3).

valve seat for runout. The total indicator reading must

(5) Operate the engine until it reaches

not exceed 0.002 inch. Clean the valve seat and

operating temperature. Adjust valve tappet clearance

as directed in subparagraph e below.

surrounding area thoroughly after grinding.

(10) After the valves and seats have been

(6) Install the valve chamber cover (7, fig.

refaced and reground, coat the seat lightly with Prussian

4-22).

e. Valve Adjustment.

blue 'and drop the valve into place, oscillating it slightly

to transfer the blue pattern to the valve face. This

(1) Operate engine until it reaches

should show a contact width of 1/ 16 to 3/ 32 inch, and

operating temperature.

should fall well within the width of the valve face,

(2) Disconnect the positive crankcase

leaving at least 1 / 64 inch on either side of the contact

ventilation valve and fittings from the valve chamber

area. If the contact area is greater than 3 / 32 inch,

cover.

narrow the contact area by grinding the outside diameter

(3) Remove the nuts and washers that

of the seal with a 15 stone or by grinding the inside

secure the valve chamber cover to the cylinder block.

diameter of the seat with a 60 or 75 stone (fig. 4-5).

Remove the valve chamber cover and gasket.

After the seat area is corrected, touch the seat lightly

(4) With the engine at operating

with the original grinding stone to remove the burred or

temperature: and running at idle speed, set the intake

feathered edge.

valves for; 0.014-inch clearance as follows:

(a) Alternately pass a 0.013-inch and

a 0.015-inch flat feeler gage between the head of the

adjusting screw of the tappet (13, fig. 4-3) and stem of

valve (2).

(b) If a 0.013-inch feeler gage moves

freely back and forth in gap when the valve is not being

lifted and 0.015-inch feeler gage binds at all times, the

clearance requires no adjustment.

gripped at all times, the clearance is insufficient.

(d) Hold valve lifter with an open end

wrench while using a second wrench to turn adjusting

screw one-quarter to one-half turn clockwise. Repeat

clearance check and adjustment until proper clearance

is obtained. The adjustable-type valve lifters have self-

locking adjusting screws that require no lock nuts.

(e) If 0.015-inch feeler gage moves

Figure 4-5. Narrowing valve seat.

freely when valve is not being lifted, the clearance is too

great. 'Hold valve lifter with an open end wrench while

(11) Inspect the spring retainer seats,

using a second wrench to turn valve lifter adjusting

spring retaining locks, valve stem caps, and valve

screw counterclockwise one-quarter to one-half turn.

tappet assemblies for cracks, scoring, overheating, and

Repeat the clearance check, and adjustment until proper

wear. Replace damaged parts.

clearance is obtained.

d. Installation.

(5) Adjust the exhaust valves to a 0.016

(1) Position the valve tappet assemblies

(hot) clearance in the manner described above, using

(13, fig. 4-3) in the engine block.

0.015and 0.017-inch feeler gage.

(2) Assemble-the valves (2 and 7), valve

4-5.

Intake and Exhaust Manifolds

springs (5 and 10), spring retainers (4 and 9), valve

a. Removal and Disassembly.

rotators (3 and 8), and valve locks (1 and 6). Compress

(1) Remove the carburetor from the intake

the valve springs with a spring compressor to install the

manifold (TM 5-4320-258-12).

valve locks. Turn the engine over as necessary to allow

each valve to move to the closed position before

attempting to install the valve parts. Make sure each

4-9