e.
Inspect interior of nitrided barrel for barrel glaze and a possible ring wear step at the point where the piston reverses travel at the top of the stroke. Repair of these items is fully described in Service Instruction No. 1047.are
5-25. Cylinder Barrel (Dimensional Inspection). Dimen-sional inspection of the barrel consists of the following measurements (the numbers in parenthesis refer to the ap-plicable reference numbers in the Table of Limits):
a.
Fit between piston skirt and cylinder (519).
b.
Maximum taper of cylinder walls (520).
c.
Maximum out-of roundness (521).
c.
Maximum out-of-roundness (521).
d.
Bore diameter (522).
NOTE
All measurements involving cylinder barrel diameters must be taken at a minimum of two position 90 ° apart in the particular plane being measured. All measurements of nitrided barrels must be made in the straight portion below the starting point of the choke, or at least two in-ches below the top of the barrel.
NICKSOR SCRATCHS IN THIS AREA ARE CAUSE FORREJECTION,BUT NORMAL WEARCAUSEDBY THE VALVE KEYIS ACCEPTABLE
002 IN.UNDERSIZEDIA.
PERMISSIBLEIN THIS AREAON INCONEL VALVESONLY.
Figure 5-6. Area to Inspect Valve Stems
Cylinder,Piston
andValveTrain 5-26. Piston (Visual Inspection). Examine the top of the piston for excessive pitting, cavaties or surface distortion. The latter may be evidence of detonation, particularly if
the piston has been in service for a relatively short time.
Other critical points which must receive thorough visual examination are the piston ring lands and grooves, piston pin holes, and piston pin holes bosses.
5-27 Piston (Dimensional Inspection). Make the following
dimensional checks on each piston (the numbers in paren-thesis refer to the applicable reference numbers in the Table of Limits).
Table of Limits).
a. Side clearance between piston ring and piston (514, 515 and 516). Pistons for Lycoming opposed engines are ground with a slight taper from the skirt to
ground the the the
with exception of lands between
the head, with the exception of the lands between the
top compression and oil control rings, which are ground parallel. The clearance on wedge type compression rings therefore must be measured as shown in figure 5-4in order to obtain a true check of the side clearance.
b.
Inside diameter of piston pin hole (512).
c.
Clearance between piston skirt and cylinder and piston diameter at top and bottom (519).
5-28.Piston Pin and Piston Pin Plugs. Check OD of piston pin against ID of hole in piston (reference 512, Table of Limits). Measure fit between piston and plugs and check OD of plugs (reference 513, Table of Limits). Examine in-terior surfaces of piston pin for corrosion or pitting.
5-29. Valve Rockers. Damaged, badly worn, pitted or scored top and push rod sockets warrant replacement of the rocker. Rockers that are scored at the point of contact with the fulcrum must be replaced.
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