(d) Inspect the sharp edge of tapered valve
guides for chips, cracks, burs; if damaged, mark for
(3) Valve springs. Weak valve springs may
cause valve flutter which results in excessive wear on
both valve and seat. Valve flutter interferes with valve
timing and may cause valve to strike the piston head.
Valve warping, cracking and breaking are the results
of weak valve springs.
(a) Test valve spring on spring tester that is
capable of very accurate measurements of spring
lengths by means of standards as listed in table 2-2 and
(b) One spacer may be used under valve
spring when insert and valve have been refaced to make
Figure 3-148. Checking push tube ball end with radius
valve check within load limit.
Figure 3-150. Minimum valve head rim thickness.
Figure 3-149. Checking push rod socket end with
(c) Collet recesses are worn so new collets
will not fit securely in recesses.
(2) Valve guides.
(a) A plug gage is not satisfactory to gage
worn holes. It will not detect an out-of-round hole.
Instead use a small bore gage.
(b) To use a small bore gage, set it with
Figure 3-151. Valve stem measurement.
replacement limit shown in table 2-2. Then use bore
several points crosswise and endwise of head.
(c) If old valve guides are worn beyond wear