CONTROL GP-FUEL RATIO 7N5486 - Caterpillar

All 3400 Series EnginesIn the past, three different piston and connecting rod designs have been used in these engines. The three different designs are straight side, narrow taper and wide taper. These descriptions make reference to the sides of the connecting rod in the pin bore area. The narrow taper is a 6° angle and the wide taper is a 9° angle. Also, the straight side DI pistons have recessed areas for the valves. The narrow taper and wide taper DI pistons do not.
All the different designs of connecting rod and piston groups (includes piston pin) have the same weight and balance. Because of this, connecting rod and piston groups of different designs can be used in the same engine. But, straight side or narrow taper designs can not be used in engines which were originally built with the wide taper design.
If an engine is changed from PC to DI or the horsepower rating is increased, the connecting rods and pistons must be correct for the new engine arrangement. The parts book microfiche will show the correct parts.
Chart B shows the part numbers of the connecting rod assemblies, piston body assemblies, piston ring groups and piston pins for all 3400 Series Engines. In Chart C, an "X" shows the acceptable combinations that the different pistons and rods can be used in. When pistons and rods of different designs are used together, make sure the correct piston pin is used with the piston.
Identification
The part number for the connecting rod assembly is put on the bottom of the connecting rod cap. Do not use the forging part number which is on the web of the connecting rod. The connecting rod forging may be used to make several different rod assemblies.
The pistons can be identified by the part number on the top. Identification of the piston pins must be made by their length. They do not have a part number on them. The lengths for the current pins are shown in Chart A that follows.