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aI, checking for possible cracks or fractures. Check
drain holes and Helicoils for damage.
(5) Crankshaft and Connecting Rods.
a. Remove counterweights. Inspect all damper pins
and bushings for wear.
b. Inspect propeller bolt bushing threads.
c. Inspect all crankpins and main journals for burn-
ing, scoring, galling and excessive wear. (Refer to
Section 13 for limits.)
d. Inspect oil tubes for obstructions, and check
tightness of tubes, bushings and plugs.
e. Measure run-out of center journals and propeller
flange. (Refer to Section 13.)
f.
Polish crankpins and journals. Inspect by Magna-
flux with circular magnetization.
If in doubt, de-
magnetize longitudinally.
Plug oil
holes
before
magnetizing.
g. Inspect all connecting rods and caps for cracks,
check alignment of crankshaft bushing with piston pin
bushing. The crankshaft hole and the piston pin hole
must be parallel with each other within .001 inch per
inch of length.
(6) Pistons and Piston Pins.
a. Check piston pin plugs for smoothness, wear and
proper fit in the piston pins. Discard piston pin plugs
which are cracked or show excessive wear. If plugs
are pressed in d'iscard assembly.
b. Check piston pins carefully for cracks, using
magnaflux equipment.
Also check piston pins for
scoring, flat spots, out-of-round, straightness and
for proper fit in piston.
Piston pins which are
cracked, our-of-round, bent, scored, or excessively
worn must be replaced.
c. Inspect pistons visually for corrosion, cracks,
burning, scored or galled skirts and piston pin bear-
ings. Check ring lands for cracks by applying light
side pressure. Measure skirt diameters and pin bores
for comparison with mating parts. Install new rings
of standard or proper oversize, and measure side
clearances. Also measure gaps of new ring in cy-
linder barrels. (Refer to Section 13 for all limits.)
(7) Crankcase Cover.
a. Inspect cover for cracks, particularly around
stud holes, by using a magnifying glass and if neces-
sary, by etching any doubtful portions for possible
cracks. Inspect magneto mounting flanges for cracks,
corrOSion, burrs, scratches and flatness.
b. Check all studs on cover for cracks and tightness.
Stretched or loose studs must be replaced.
c. Inspect threads for oil pressure relief cap and oil
screens.
d. Inspect oil pump impeller and shaft bores in
casting, shaft bores in cover plate and plate surface
for scoring and wear.
(8) Camshaft.
a. Inspect cam lobes and journals for scoring, wear
and pitting. Inspect screw holes.
(9) Gears.
a. Check magneto, starter, generator, oil
pump,
camshaft and crankshaft gears for cracks, nick;:"
burrs, wear and proper fit. Inspect camshaft gear,
crankshaft gear and magneto gears by Magnaflux for
fatigue cracks.
Section 11
REPAIR AND REPLACEMENT
1. GENERAL RE PAIR.
2. CASTINGS. Remove the raised edges of nicks and
burrs on machined surfaces with a hard Arkansas
stone.
Unobstructed flat surfaces, such as cover
plates etc. may be returned to true flatness if a
lapping plate is available. Use a fine grade lapping
compound and move the part in a figure 8 motion
evenly.
3. STUD REPLACEMENT. Remove damaged whole
studs with a standard stud remover or a small pipe
wrench. Turn slowly to avoid over heating. Remove
broken studs which cannot be gripped by drilling on
center to the correct diameter for and unscrewing
them with a splined stud extractor.
(Splined ex-
tractors and drills are usually sold in sets.) Examine
the coarse thread end of the damaged stud to deter-
mine its size. Standard studs have no marking. For
oversize stud identification refer to Table XI.
Clean
the tapped hole with solvent and blow dry with com-
pressed air; then examine the thread.
If it is not
damaged install the next larger oversize stud. If the
old stud was maximum oversize, or if the thread is
damaged, the hole may be tapped and a helical coil
insert installed for a standard size stud.
Coat the
new studs coarse thread with Alco Thread Lube if the
hole is blind or with National Oil Seal Compound if it
is a through hole that is subject to oil spray. It is
advisable to drive the new stud with a tee handle stud
driver. Turn it slowly, and compare the estimated
torque with values listed in Section 13.
Drive the
stud in until it projects a distance equal to others in
the same group.
4. HELICAL COIL INSERT INSTALLATION. Helical
coil thread inserts are factory installed at various
locations.
These inserts may be replaced, if dama-
ged, with the aid of special tools procurable from any
Authorized Distributor of the "Heli - Coil" Corporation.
5. These inserts are helical coils of wire with a dia-
mond shaped cross section forming both a male and
female thread. Drilling and tapping depths for inserts,
being installed in blind holes, should be equal to twice
the nominal diameter of the insert. The helical coil
drills and taps must be absolutely perpendicular to the
machined surface of the casting. Drilling should be
accomplished in a drill press after the casting is
firmly supported, clamped and alignment checked.
For drilling and tapping aluminum alloy castings, use
a lubricant made of one part lard oil and two parts
kerosenetoprevent overheating the metal and tearing
the thread.
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