VALVE MECHANISM GP 7N8024 - Caterpillar

(90U),
3406B (6TB) Industrial Engines;
3406B (2WB, 4RG) Generator Set Engines;
3406B (4TB) Marine EnginesThis article identifies the major engine component changes that have taken place since 1991.
Crankshaft, Connecting Rod, Bearings, Dampers
The new 4P4334 Crankshaft Assembly (wide journal), the corresponding 9Y7735 Connecting Rod Bearing (wide) and 9Y6400 Connecting Rod Assembly (except 2WB and 4RG), and the 4P4297 Damper (bonded rubber) or 7E9520 Damper (visconic) are in effect as shown in Chart A. The use of the bonded rubber or visconic damper depends on engine rating and application. The new 4P4334 Crankshaft Assmebly can be used in any 3406 block with the corresponding rods, bearings, and damper.
The 9Y6400 Connecting Rod Assembly was canceled and replaced by the 7E5996 Connecting Rod Assembly. The 7E5996 Connecting Rod Assembly is in effect as shown in Chart B. The rod cap is fastened to the rod with bolts and nuts on the 9Y6400 Connecting Rod Assembly. On the 7E5996 Connecting Rod Assembly, the rod cap is fastened to the rod with bolts that thread into tapped holes in the rod. The 9Y6400 Connecting Rod Assembly and the 7E5996 Connecting Rod Assembly can be intermixed in the same engine. These rod assemblies have different tightening specifications.
* On the 9Y6400 Connecting Rod Assembly, the nuts should be tightened to 80 8 N m (60 6 lb ft), and then the nuts should be tightened an additional 1/3 turn.* On the 7E5996 Connecting Rod Assembly, the bolts should be tightened to 90 8 N m (66 6 lb ft), and then the bolts should be tightened an additional 1/4 turn.Engines that are built, repaired, or overhauled with the new 9Y6400 Connecting Rod Bearings, DO NOT require a mid-life connecting rod bearing roll-in if the following conditions are NOT encountered:
* Extended operation at high load factors.* Extended operation at high rpm (2100 rpm and above).* Excessive lead or aluminum in oil samples.* Reuse of Crankshaft with marginal profile or surface texture.* Engine overheating.* Oil dilution by fuel or coolant.* Rapid cold engine starts.* Dry starts after an engine has set for 30 or more days without prelubing.* Extended oil drain intervals causing excessive lube oil sooting.* Plugged oil filters.* Incorrect oil viscosity (too light during hot weather, or too heavy during cold weather).If these or similar conditions cause marginal lubrication to an engine, Caterpillar recommends the bearings be inspected and/or replaced.
The service replacement bearing for the "tee-pee" end of the connecting rod is the 4P8495 Bearing. This bearing has side reliefs that allow more oil into the piston pin/bushing interface than the former 8N2018 Bearing.
The 7E5665 Piston Pin Retainer replaces the forner 8N7295 Piston Pin Retainer. The new retainer has increased groove contact to help keep it from being "popped out" and to prevent it from wearing the groove. The new retainer was in effect as shown in Chart C.
Cylinder Block
The new 7E9432 Cylinder Block (casting part number) has been redesigned to improve upper deck cooling. This provides additional cooling paths to the piston rings. The