Cat C15 Valve Lash Specs & Overhead Adjustment (6NZ/ACERT)
Factory OEM valve lash clearances, feeler gauge sizes, Cat 9U-7227 injector height, and cold overhead adjustment procedures for Caterpillar C15 engines.
2-Turn Crankshaft Adjustment Protocol
Firing Order: 1-5-3-6-2-4Select engine stroke position below to highlight exact cylinders, valves, and injectors ready for adjustment:
Cat C15 (6NZ / BXS / MXS) Cold Valve Clearance Standards
Overhead adjustment must strictly be performed with coolant temperature below 140°F (60°C). Valve lash tolerances:
Cat C15 Unit Injector Timing Height (78.0mm) & Jake Brake Slave Lash
Electronic Unit Injector (EUI) height must be dialed using Caterpillar fixture 9U-7227 from the machined ledge of the injector body to the top of the injector follower:
| Component / System | Imperial Clearance | Metric Clearance | Specialty OEM Tool Required |
|---|---|---|---|
| EUI Injector Timing Height | 3.071 ± 0.008 in | 78.0 ± 0.2 mm | Cat 9U-7227 / 136-4632 Dial Indicator |
| Jake Brake Slave Piston Lash | 0.027 in | 0.69 mm | Cat slave feeler gauge, torque locknut to 25 lb-ft |
| Valve Adjuster Locknut Torque | 25 lb-ft | 34 N·m | Hold screw stationary while torquing nut |
Cat C15 2-Revolution Crankshaft Setting Order (Flywheel Pin Position)
Engage flywheel timing pin into timing hole at Top Dead Center (TDC) Compression Stroke Cylinder 1. Adjust intake valves on cylinders 1, 2, 4; exhaust valves on cylinders 1, 3, 5; and injectors on cylinders 3, 5, 6.
Remove timing pin, rotate crankshaft 360 degrees counterclockwise to TDC Compression Stroke Cylinder 6, and reinstall pin. Adjust intake valves on cylinders 3, 5, 6; exhaust valves on cylinders 2, 4, 6; and injectors on cylinders 1, 2, 4.
Frequently Asked Questions & OEM Service Guidelines
Verified answers according to official factory service literature and heavy-duty maintenance procedures:
Q: Can Caterpillar C15 cylinder head bolts be reused?
Caterpillar SEBF guidelines state that C15 head bolts may be reused up to a maximum of 2 times provided free length does not exceed 10.125 inches (257.2 mm) and threads are free of necking or pitting.
Q: What lubricant is required when torquing Cat C15 head bolts?
Clean SAE 30W engine oil must be applied to bolt threads and the underside of bolt head flanges. Never use anti-seize or thread sealant unless specifically instructed by OEM TSB.
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