How Do You Reuse Cummins ISX and QSX Connecting Rods? - Engine Builder Magazine
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How Do You Reuse Cummins ISX and QSX Connecting Rods?

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There are two types of ISX & QSX connecting rods; “Drilled” and “Non-Drilled”. A drilled
connecting rod has an oil passage drilled up through the shank of the rod to supply lubrication to
the connection at the piston pin. A drilled rod can be used with either two piece articulated or
one piece steel pistons. There is no oil passage in a non-drilled rod, and this type of rod can only
be used with two piece articulated pistons. Because of the differences in the connecting rods,
they require different connecting rod bearings, which cannot be interchanged between the two
rod types.
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Reusability Guidelines:

Thoroughly checking a connecting rod and connecting rod bolts requires sophisticated
equipment and fixtures found in engine machine shops. Machine shops have the capabilities to
MagnafluxTM the rod and/or bolts to indentify cracks, check the rod to see if it is bent or twisted,
and check the length from center to center.

• Maximum allowance for bend is 0.0008? (0.021mm).

• Maximum allowance for twist with the bushing installed is 0.002? (0.05mm).

• The length specification of the connecting rod from center to center is 10.293? to 10.297? (261.45mm to 261.55mm).

Often, connecting rods removed from non-failed running engines are visually inspected and
checked dimensionally to assure the bores are within specifications, and then reused. Once the
rod & bolts are cleaned and dried, including the oil passage of drilled rods, the remainder of this
tech bulletin outlines the steps commonly performed by the technicians at the repair or rebuild
facilities.

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• Visually inspect the rods and bolts

o There should not be any damage to the shank or I-beam of the rod or to the cap.

o There should not be any damage to the thrust face or chamfered areas of the rod or cap.

o The mating surfaces at the parting line of the cap and rod must not be fretted or damaged.

o The bearing surfaces must free of nicks and burrs (small imperfections can be removed with emery cloth).

o The rod pin bushing must not be damaged or have indications that it has turned in the rod.

o Some amount of discoloration is acceptable, but if the rod & cap have a bluish color, the rod assembly should be replaced.

o Assure that the alpha codes match between the rod & cap.

o The bolts cannot have damaged treads, or be pitted from rust or corrosion.

o The bolts cannot be bent or galled.

o The bolt seat and mating seating area of the cap must not be fretted or damaged.

• Dimensional Specifications

o Connecting rod bearing bore (big end) specification is 3.890? to 3.891? (98.801mm to 98.839mm). Note that the torque procedures are different
between new rod bolts and used rod bolts.

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? The procedure for used rod bolts is to tighten the bolts in numeric
sequence to 52 ± 4 foot pounds, and then in sequence, add an additional
60 ± 5 degrees turn.

? The procedure for new rod bolts is to tighten the bolts in numeric
sequence to 29 ± 4 foot pounds, loosen the bolts in numeric sequence,
retighten the bolts in numeric sequence a second time at 52 ± 4 foot
pounds, and then, in sequence, add an additional 60 ± 5 degrees turn.

o Connecting rod bushing (small end) bore specification for the inside diameter
of the bushing to accept the piston pin is 2.502” to 2.503” (63.55mm to
63.57mm).

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? Note, at the time of this bulletin, replacement bushings and the
procedure for replacing them is not available.

The drilled connecting rod was introduced in late 2002, and has since replaced the earlier non-
drilled rod. As stated above, the drilled rod can be used with both two piece articulated and one
piece steel pistons. It can also be mixed with non-drilled rods in engines with two piece
articulated pistons only. Again, a drilled rod must be used in all one piece steel piston
applications.

 More detailed information can be found in the O.E. service bulletins. Always consult the latest
O.E. service bulletins and publications for the updates and current information.

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Tech Tip courtesy of IPD.

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