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CRANKSHAFT/TRANSMISSION 9-15
Crankshaft and Connecting Rods
(1) Bolt Length Measurement Method
•
Be sure to clean the bolts, nuts, and connecting rods
thoroughly with a high-flash point solvent, because the
new connecting rods, bolts, and nuts are treated with an
anti-rust solution.
WARNING
Clean the bolts, nuts, and connecting rods in a well
-ventilated area, and take care that there is no spark
or flame anywhere near the working area. This in-
cludes any appliance with a pilot light. Because of
the danger of highly flammable liquids, do not use
gasoline o r low-flash point solvents to clean them.
CAUTION
Immediately dry the bolts and nuts with com-
pressed air after cleaning.
Clean and dry the bolts and nuts completely.
•
Install new bolts in reused connecting rods.
•
Dent both bolt head and bolt tip with a punch as shown.
•
Before tightening, use a point micrometer [A] to measure
the length of new connecting rod bolts and record the v al-
ues to find the bolt stretch.
Connecting Rod [B]
Mark here with a punch [C].
Nuts [D]
Fit micrometer pins into punch marks [E].
•
Apply a small amount of molybdenum disulfide oil to the
following:
Threads of Nuts and Bolts
Seating Surfaces of Nuts and Con-rods
•
Tighten the big end nuts until the bolt elongation reaches
the length specified in the table.
•
Check the length [F] of the connecting rod bolts.
If the stretch is more than the usable range, the bolt has
stretched too much. An overelongated bolt may break in
use.
Bolt Length Bolt Length
after tightening
–
before tightening
=
Bolt Stretch
Connect-
ing Rod
Assy
Bolt Nut
Usable Range of
Connecting Rod
Bolt Stretch
Attached to
new con-rod
New
Use the bolts
attached to
new con-rod.
New
0.24 ∼ 0.36 mm
(0.0094 ∼ 0.0142
in.)
Used
Used
Replace the
bolts with new
ones.
New
0.20 ∼ 0.32 mm
(0.0079 ∼ 0.0126
in.)