Caterpillar 3304 & 3306 Diesel Engine Service & Maintenance Manual
Instant Answer & Quick Specs Box
Engineering Overview & Technical Coverage
The Caterpillar 3304 (inline-4, 7.0L) and 3306 (inline-6, 10.5L) diesel engines represent one of the most rugged, widely deployed industrial diesel families in history. Used across Cat track-type tractors (D6D, D7G), motor graders (12G, 140G), wheel loaders (966D, 980C), hydraulic excavators (235, 330), and marine/generator applications, the 3300-series features precombustion chambers or direct injection, heavy cast blocks, and mechanical scroll fuel systems. This comprehensive 316-page factory service manual covers disassembly, component wear limits, cylinder head torquing, and governor adjustments.
Critical Engineering Specifications & Tightening Sequence
| Component / Fastener | Thread Size | Imperial Specification | Metric Specification | Assembly Procedure / Notes |
|---|---|---|---|---|
| Cylinder Head Bolts (Final) | 3/4″-16 | 185 lb-ft + 90° Turn | 250 N·m + 90° Turn | Torque 1-18 in sequence to 115 lb-ft, then 185 lb-ft, then +90° turn |
| Main Bearing Cap Bolts | 7/8″-9 | 190 lb-ft + 120° Turn | 258 N·m + 120° Turn | Lube threads with clean engine oil. Check crank end play 0.003–0.010″ |
| Connecting Rod Bolts | 9/16″-18 | 30 lb-ft + 90° Turn | 40 N·m + 90° Turn | Check rod side clearance (0.010–0.021″) |
| Intake Valve Lash (Cold) | Feeler Gauge | 0.015 in | 0.38 mm | Adjust with rocker locknut torqued to 22 lb-ft (30 Nm) |
| Exhaust Valve Lash (Cold) | Feeler Gauge | 0.025 in | 0.64 mm | Adjust cold at top dead center firing positions |
| Precombustion Chamber (PC) | Head Bore Spline | 150 ± 10 lb-ft | 205 ± 14 N·m | Install with liquid gasket sealant on lower chamber threads |
| Flywheel Mounting Bolts | 5/8″-18 | 155 ± 10 lb-ft | 210 ± 14 N·m | Cross star pattern tightening to maintain flywheel alignment |
Complete Service Chapter Directory
- Systems Operation & Specifications: Air inlet & exhaust piping, lubrication circuit, fuel pump & governor mechanical actuation, and coolant circulation diagrams.
- Testing & Adjusting: Crankshaft timing pin alignment, fuel injection pump timing by spill method, fuel rack setting measurement, and oil pressure relief valve adjustments.
- Disassembly & Assembly – Cylinder Block: Main bearing journal wear tolerances, cylinder liner projection (0.003–0.006 in), piston ring end gaps, and crankshaft seal installation.
- Cylinder Head & Valvetrain: Valve guide reaming, valve seat grinding, spring tension inspection, rocker shaft alignment, and 3304/3306 cylinder head torquing sequences.
- Fuel Injection System: Fuel injection pump housing overhaul, plunger & barrel wear checks, governor spring calibration, and precombustion chamber resealing.
- Lubrication & Cooling Systems: Gear-driven oil pump inspection, oil cooler bundle ultrasonic cleaning, water pump impeller shaft and carbon face seal replacement.
Heavy Equipment Mechanics: Free Interactive Calculation Suite
Calculate fastener stretch, torque unit conversions (Nm to ft-lbs), engine displacement, and compression ratio online in seconds:
Open Diesel Mechanic Calculators →Frequently Asked Questions
What is the cylinder head bolt torque on a Caterpillar 3306 engine?
The cylinder head bolts on Caterpillar 3304 and 3306 engines follow a torque-turn sequence: first tighten all bolts in numerical sequence to 115 lb-ft (155 N·m), then tighten to 185 lb-ft (250 N·m), and finally apply an additional 90-degree turn to each bolt.
What are the cold valve clearance adjustments for Cat 3306 engines?
With the engine cold, adjust the intake valve lash to 0.015 in (0.38 mm) and the exhaust valve lash to 0.025 in (0.64 mm).
