TRUCK SERVICE MANUAL
ENGINE
4. Insert mandrel with all components listed in Step "2"
6. Adjust the guide screw (up or down) until tool bit just
into connecting rod bushing bore.
engages bore.
5. Align Detail (4) with middle of boss on rod.
Note: A slight pressure is required against guide screw.
Note: Be sure to line up oil holes.
To obtain this pressure, tighten set screw in end of holder
against guide screw.
6. Using an arbor press,. press bushing into bore until
7. Insert drive ratchet and turn tool one complete turn to
Detail (4) contacts side of rod pin boss.
clean up edge of bore.
7. To install thick-walled bushings in rods which have
8. Loosen guide screw and again turn tool one or more
been resized at crankpin end, install in same manner as
complete turns to give a clean cut.
outlined in Steps 2 through 6 above.
Note: Repeat until a uniform chamfer of 0. to 0.060 inch
Bore Rod Piston Pin Bushing
[1.02 to 1.52 mm] depth is reached.
1.Fill lubricating holes with soap to keep out shavings.
9. Remove tool from bore, turn rod over and chamfer
2. Mount connecting rod in ST-526 Tobin-Arp Boring
other side of bore.
Machine or equivalent.
10. With both sides chamfered, remove tool.
Note: Lower mandrel should have only the two horizontal
11. Use emery cloth to remove any sharp edges which
blades in place to properly locate the side position of the
may have been left on chamfer.
piston pin end of rod.
12. Wash rod before bushing installation.
3. See instruction booklet furnished with ST-526 for
operating procedure.
PISTONS AND PISTON RINGS
4. Bore bushing to 2.001 to 2.0015 inch [50.83 to 50.84
Piston Rings
mm] inside diameter. Remove rod from ST-526 and check
New rings should be checked in cylinder liner in which they are
size with ST-205 Plug Gauge.
to be used to make sure the gaps are correct.
5. Remove sharp edges with a scraper.
1. Insert each ring in mating cylinder liner; position with
6. Remove shavings and soap, wash in mineral spirits
head of piston so it is seated squarely in ring travel area of
and dry with compressed air.
liner.
7. Check all dimensions on rebushed and rebored rods
2. Measure ring gap with a feeler gauge. Gap should fall
on ST-561 Checking Fixture as previously described.
within limits given in Table 1-1 (14).
Note: All connecting rods used in an engine should have the
3. Never file or stone chrome-plated rings and never use
same part number and letter code.
Never attempt to
chrome-plated rings in chrome-plated cylinder liners.
interchange caps.
4. Check current parts catalogs to assure use of proper
Chamber Piston Pin Bore
ring/piston combination.
When used, chrome-plated
compression ring is always installed in top piston ring groove.
1. ST-861 Chamfering Tool is used to chamfer tapered
piston pin bushing bore, if not chamfered.
2. Install proper bushing tool detail by use of flat-head
INSPECTION
screw.
1. Check top and second ring grooves with ST-560 Ring
3. Set the guide screw holder. in position; there are three
Groove Gauge. Shoulders of gauge must not touch ring
notches, so guide screw wi ll follow on face of bore.
groove lands if piston is to be reused. If shoulders touch,
4. Adjust tool bit until point just clears guide screw and
discard piston.
tighten in position with two set screws.
2. If ST-560 is not available, check wear with a segment
5. Install unit into bore.
of a new ring and a feeler gauge.
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