Valve and Valve Seat Grinding.

(d) Grinding wheels of 30, 45, and

If clearance is less than specified minimum, guides must

be reamed to obtain proper clearance. Inside diameter

60.

of valve guide is 0.343 inch to 0.344 inch.

(5) Install tool pilot in position in valve guide.

(10) Valve seat inserts (21 and 22) are

Use a 45 grinding wheel for refacing valve seat and use

the 30 to 60 grinding wheels for narrowing the seat

replaceable. Standard seats are available for service.

Inspect valve seat inserts. If loose, cracked, or pitted

width to the specified 1 / 16 inch for intake and 3 / 32

new inserts must be installed. Inserts are a shrink fit in

inch for exhaust valve seats.

cylinder head. Remove insert shown in figure 3-36 by

(6) After a grinding wheel has been used

electric welding a bead around inside circumference of

several times, cutting angle of stone must be reground

insert on beveled portion. Allow insert to cool, then lift

and made true to obtain proper seat angle.

out.

(7) After valve seats have been ground, use

CAUTION

dial gauge to check concentricity of valve seats relative

Protect machined surfaces from arc

to valve guides. Total runout of valve should not exceed

splatter.

0.002 inch.

(11) Care must be exercised when installing

(8) After valve seats have been ground,

new valve seat inserts. Inserts are installed into cylinder

valves may be inserted in position in cylinder head and

head with a 0.0025 inch to 0.0045 inch shrink fit and

lapped in place, using fine grain valve lapping

must be started in place "true" with counterbore in

compound. After lapping, contact between valves and

cylinder head.

seats may be checked by wiping a thin film of Prussian

(a) Be sure insert counterbores in

Blue on each valve seat, setting valve in place, and

cylinder

bouncing each valve once on its seat.

head are clean and free of burs.

NOTE

(b) Thoroughly chill insert with dry ice.

Do not revolve valve when checking

seat.

air and start insert into counterbore (valve seat side up).

(9) If valve seats are properly ground, a

(d) Using a valve seat installer tool,

continuous thin blue line will be evident around face of

drive insert down tight into counterbore. This operation

valve.

must be done quickly, while insert is cold.

After

(10) Clean valves and block and install valves

installation, stake valve seat in position with a center

h above.

punch at two or three points around edge of seat..

(11) Install cylinder head (para 3-20).

(e)

It will be necessary to refinish valve seat

3-24. Camshaft, Bearings, and Valve Lifters

inserts with a grinder ( i below).

a. Description. The camshaft is manufactured of

i. Valve and Valve Seat Grinding.

drop forged, open hearth steel. case hardened at the

(1)

Before installing new valves or valves

cams and journals, and is located in the rightside of the

previously used, valve seats in cylinder head should

engine block (as mounted in truck). Rigidly supported by

be inspected for proper valve seating.

four replaceable bronze bearings, the camshaft's end

previously used valves are to be reinstalled, valve stems

play is controlled by an end thrust plate at the timing gear

should be cleaned and valve faces ground to an angle of

end. The valve lifters ride on precision ground cams of

45. When refacing valves, remove just enough to clean

the shaft and provide the timing link between the

up seat, removing all evidence of pitting and grooving.

camshaft and valves through the push rods and rocker

(2)

Valve guide should be cleaned with a

arm assembly. The camshaft bearings seldom need

valve guide cleaning tool.

If bore of valve guide is

replacement or repair, and since it is necessary to

worn oblong, or if valve head is warped relative to valve

disassemble the entire crankcase to effectively check

stem, damaged parts must be replaced.

bearing to camshaft clearances, it is recommended that

(3) When new valve seat inserts are installed,

camshaft bearings be checked every time crankcase

or previously used inserts refaced, refinishing must be

disassembly allows access to the camshaft and

done with a valve grinder set because of very hard valve

bearings.

seat material.

b. Removal.

NOTE

It is very important that valve grinder

It is recommended that camshaft be

set

used

according

replaced only when engine is removed

from truck. However. in an emergency it

manufacturer's directions.

is possible to replace it without engine

(4) The usual equipment furnished with the

removal. Instructions below apply to

valve seat grinder set includes the following items:

both methods. however. if engine has

(a) Valve seat grinder.

already been removed from truck.

(b) Dial gauge.

disregard (a) and (e).

3-48