SEAL 8T7134 - Caterpillar

All 5.4"
Bore EnginesCaterpillar currently uses pistons with Keystone-type rings in all 5.4" Bore Engines.
The Keystone-type rings have a better resistance to deposits which can prevent free operation of the rings. The valve pocket, machined into the top of the piston which uses the Keystone-type ring, is the same size and shape on both sides of the piston, so it is no longer necessary to install the piston in a specific position. Also, a notch is machined between the pocket and the outer circumference of the piston.
The improvements will give longer service life to the piston.
The current pistons which use Keystone-type rings can be installed in place of pistons which use rectangular type rings, in earlier engines.
If the pistons which use Keystone-type rings are to be installed, the carbon at the top of the cylinder liners must be removed with a flexible-type hone (GBD 5 1/2" in the "Tool Guide For Caterpillar Dealers" SENS5500). A single piston and rings or part of a complete set of pistons and rings can be installed in the same engine with pistons with rectangular rings.
The pistons which use Keystone-type rings can be installed in the models as shown in the chart.
If pistons with rectangular rings are used with pistons with Keystone rings, make sure the pistons with rectangular rings are installed in the correct position to prevent contact between the valves and the top of the pistons.
The "V" mark on the piston must be in alignment with the "V" mark on the block.
The 8N931 and 9N2874 Piston Body Assemblies have a weight difference of 110 grams. Also, the machined area on the crown (top) is deeper on the 8N931 Piston Body Assembly. These piston bodies can not be used in place of each other.