Exhaust valves (except Inconel exhaust valves) should never be reused. Inconel exhaust valves may be reused if they comply with requirements of the following inspec-tion.
5-32. Do not reuse valve in which stem diameter midway of valve measures less than that measured at the key end; excepting inconel valves which may be 0.002 inch under-size on stem diameter as shown in figure 5-6.
Section 5 OVERHAUL MANUAL LYCOMING
Cvlinder, Piston and Valve Train
5.33. Check mnout of valve face. See figure 5-7. Total runout must not exceed .0015 inch. Do not reuse any valves that exceed this limit.
5.34. Measure edge thickness of intake valve heads. See figure 5-7. If, after refacing. “A” is less than ,060 the valve must not he reused.
NOTE
The edge of intake value heads are genemlly formed as shown is figure 5-8. The thickness “A” can best be measured with an optical comparator; however, it can be measured with sufficient accuracy by means of a dial in- dicator and a surface plate, as shown in figure 69.
FACE OF VALVE MUST RUN TRUE WITH STEM WITHIN .0015
Figure 5-7. Valve Showing Locations for
Checking Run-Out and Section for
Measuring Edge Thickness
5.35. Using an optical magnifier. examine the valve in the stem area and the tip for evidence of cracks, nicks, tool marks. or other indications of damage. Damage of this nature seriously weakens the valve, making it liable to failure. Any valve having a nick. with ragged edges more than l/16 inch in length should not be reused. A nick or tool mark of any sort in the keeper groove of an exhaust valve is sufficient reason for not reusing the valve. See figure 5-6.
5-36. If superficial nicks and scratches in the valve in-dicate that the valve might be cracked. it should be in- spected by a magnetic particle or dye pen&rant method. Dye pa&rant procedures should be carried out strictly within the recommendation of the manufacturer of the penetrant.
5-37. Critical areas include the face and tip both of which should be examined for pitting and excessive wear. Minor pitting on valve faces can sometimes be removed by regrinding; otherwise the valve should be rejected. Replace any valve that has operated with a collapsed hydraulic tappet, regardless of the number of hours on the
76 SERIES AIRCRAFT ENGINES
Figure 5-8. Section Through Edge of Valve
valve. (See inspection of hydraulic lifters.) Cheek the clearance between the valve stem and guide (reference 528 Table of Limits for exhaust valves. and reference 529 for intake valves).
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