🏷️ Basic Information Identification Make: Franklin Model: 6A4 Series Aircraft Engine Application: Stinson Aircraft (and others) Engine Variant: 6A4-150-B3, 6A4-150-B31, 6A4-165-B3 📋 Manual Details Document Information Manual Type: Service and Repair Manual Language: English Format: PDF Download ⚙️ Engine Specifications General Engine Type: Air-cooled, horizontally opposed, 6-cylinder Displacement Displacement: 310.4 cubic inches (5.09 liters) Power Output Power Output Hp: 150 hp (6A4-150) / 165 hp (6A4-165) Bore Stroke Bore: 4.375 inches (111.1 mm) Stroke: 4.375 inches (111.1 mm) Compression Ratio Compression Ratio: 6.5:1 Cooling System Cooling Method: Air Cooling Fuel System Fuel Type: Aviation Gasoline (Avgas) Lubrication System Oil Capacity Quarts: 8 quarts (7.6 liters) 🔧 Transmission General Type: Direct Drive (typically) Gears Gear Reduction: None (direct drive) 📐 Dimensions Physical Dimensions Length Inches: 38.5 (approximate) Width Inches: 33.8 (approximate) Height Inches: 26.3 (approximate) Weight Dry Weight Lbs: 257 (approximate) 🔧 Maintenance Service Intervals Overhaul Interval Hours: 1500 (typical recommended) Oil Change Oil Change Interval Hours: 50 Spark Plugs Spark Plug Type: Champion RHB32S (or equivalent)