Usage:
All 3406, 3408 and 3412 Industrial, Marine and Generator Set Engines
Description of Change: A new piston pin retainer (snap ring) is now used in the connecting rod and piston groups on the above engines. The new retainer has a larger outside diameter in the free (relaxed) position and a wider cross section. These changes permit the new retainer to fit tighter against the diameter of the groove in the piston.
Two different retainer rings have formerly been used. The first retainer used did not fit tight enough against the diameter of the groove. This permitted the retainer to turn in the groove. This caused wear on the retainer ring and groove. In some cases the retainer had worn the groove through the bottom of the piston.
The second retainer used was a temporary replacement for the first retainer. This second retainer was the same size as the original one, but was more rigid.
Adaptable As: The new 8N7295 Retainer is a direct replacement for the former 83214 Retainer (first) and 8N8058 Retainer (second) in these engines. When a replacement of the retainers is made, both retainers on a piston must be changed. The new retainer is in effect with the serial numbers shown in the chart.
IDENTIFICATION: The retainer rings do not have a part number on them. Identification must be made by their cross section width. See the illustration. The new 8N7295 Retainer in the relaxed position has a cross section width of 4.70 ± 0.20 mm (.185 ± .008"). Both the former 83214 and 8N8058 Retainers have a width of 4.32 ± .18 mm (.170 ± .007").
The pistons in these engines can be checked to see if they are usable according to the procedure that follows.
If the groove in the piston is visibly worn, a new piston must be installed.
If the groove in the piston does not show any visible wear, install new retainers and check their fit. Check the amount of force needed to turn the new retainer in the used piston. A comparison of this force with that needed for a new retainer in a new piston can be made. If the force needed for the used piston is much less, a new piston must be installed.
Cross section area of retainer.