Description
CAT 4K-6761 Upper Cap
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The CAT 4K-6761 is a genuine Caterpillar engine upper valve cover, compatible with engines such as the 3306/C9/C11/3176C and the 815/816 series road rollers. It seals the valve chamber, prevents oil leakage, and protects the valves and rocker arms. As a critical seal in the engine cylinder head system, it must be installed according to the original manufacturer’s torque and gasket specifications to ensure reliable operation.
Key Parameters (Original Nominal Specifications; for precise engineering drawings, please contact an authorized Cat dealer)
Item Details
Part Model: CAT 4K-6761 (4K6761) Upper Cap/Valve Cover
Material & Process: Cast aluminum alloy (ZL109) precision casting + T6 heat treatment, powder coated surface (CAT gray/black); sealing surface with composite rubber gasket (recommended 127-0718), oil resistant/temperature resistant -40°C to +150°C
Structure Specifications: One-piece upper cover with 8 sets of M8 bolt holes, with PCV valve interface (some models); compatible with inline 6-cylinder/8-cylinder engine valve chambers, sealing groove width 5mm × depth 2mm
Weight: Approx. 3.45 kg (7.6 lbs); Dimensions (L x W x H): Approx. 262mm x 262mm x 41mm (precise values subject to model drawings)
Rated Operating Conditions Engine oil pressure 300–500 kPa, temperature ≤120°C; check for leaks/bolt torque every 250 hours.
Compatible Engines: Compatible with CAT 3306, C9, C11, 3176C engines; 815B/F/II, 816F/F II road rollers; final verification based on engine serial number + cylinder head model.
Installation Parameters: Bolt specification M8×1.25, installation torque 28–32 N・m, tightened in three crisscrossing stages (initial tightening 10 N・m → secondary tightening 20 N・m → final tightening 28–32 N・m).
Compatibility and Application Notes:
Functional Positioning: Seals the valve chamber, preventing oil leakage and dust/moisture intrusion, providing protection for valves, rocker arms, and pushrods; assists crankcase ventilation and balances oil and gas pressure when integrated with the PCV interface.
Matching Specifications: Must be replaced as a complete set with the original composite rubber gasket (127-0718) and bolts; mixing gaskets of different materials is prohibited. Clean the sealing surface before installation, ensuring it is free of scratches, rust, and carbon deposits.
Replacement Standards: Replace immediately if the top cover is deformed (flatness > 0.15mm), the sealing groove is damaged, the threads are stripped, or the gasket is aged/damaged. Recheck for oil leaks within 24 hours of assembly.
Installation and Maintenance Procedure: Stop the engine and allow it to cool until the cylinder head ≤ 60°C. Remove the old top cover and gasket, and clean the sealing surface (using a scraper and cleaning agent to avoid scratching).
Apply a thin layer of engine oil to the new gasket and align it with the sealing groove. After the top cover is in place, tighten the bolts to the rated torque in three diagonal steps.
Start the engine and allow it to idle for 15 minutes, checking for leaks on the sealing surface. After the engine is warm (80°C), recheck the torque; if the deviation exceeds ±5%, readjustment is required.
Maintenance cycle: 250 hours under standard operating conditions; 150 hours under high load/high temperature operating conditions, check for leaks/PCV valve patency.
