BREATHER 1833873 - Caterpillar

Four different pistons are used in 3406B Truck Engines. The piston used will depend on many factors, including horsepower rating, engine arrangement and engine application. Chart A gives some of the uses and design features of the different pistons and includes the 7C490 Basic Piston Group used in CARB (California Air Research Board)/ATAAC (air-to-air aftercooled) engines and the "new" 7C4473 Basic Piston Group used in 310 hp family.
The 7C490 Basic Piston Group is used in the 400 horsepower arrangement of 3406B CARB/ATAAC Truck Engines. CARB truck engines are designed to meet the stricter emission standards required for trucks operating in the state of California. A high ring position and a tight top land (reduced clearance between piston and cylinder liner) are combined to reduce the dead air volume in the cylinder and provide increased combustion efficiency. A plasma coated top ring is used for necessary scuff and wear resistance. An "offset" wrist pin bore helps control piston slap in the cylinder liner.
"Offset" pistons have the word FRONT marked on the top of the piston for installation purposes.
The 7C4473 Basic Piston Group is now used on all 310 hp family, 3406B Truck Engines (except CARB/JWAC arrangements). This design contains a rectangular second ring which improves the control of oil consumption. The single iron band (for the top ring only) will result in lower stresses in the piston casting and lower piston weight. See Footnote 1. A plasma top ring is now used to ensure long reliable life.
It is important to observe all lubrication system maintenance recommendations listed in the Operation And Maintenance Management Guide. The following factors can directly affect the overall life of your Caterpillar Truck Engine: 1. Load factor (indicated by fuel consumption)2. Lube oil quality (initial oil quality, oil change interval, filter quality, etc.)3. Lube oil quantity (sump size and oil addition)4. General maintenance quality (fuel system, cooling system, etc.)5. Fuel quality (sulphur, water, etc.)