The Isuzu 6H is a family of inline six-cylinder diesel engines installed in Isuzu medium-duty trucks, and also installed in GM medium-duty trucks as the Duramax LG4. It is mated to the Allison 2500, 3000, and 3500 series transmissions.

6HK1/Duramax LG4

• Displacement: 7.8 L; 475.4 cu in (7,790 cc)
• Bore and stroke: 115 mm × 125 mm (4.53 in × 4.92 in)
• Block: Gray iron
• Cylinder head: Cast iron
• Fuel cutoff: 2400 rpm
• Aspiration: Turbocharged and intercooled
• Valvetrain: SOHC 24-valve
• Compression: 17.5:1 (17.0:1 for 300 hp (224 kW))
• Injection: high-pressure common-rail direct injection
• Power/torque: 200–300 hp (200–300 PS; 150–220 kW), 520–860 lb⋅ft (72–119 kg⋅m)^[1]

6HH1

• Displacement: 8.2 L; 502.0 cu in (8,226 cc)
• Bore and stroke: 115 mm × 132 mm (4.5 in × 5.2 in)
• Aspiration: Naturally aspirated
• Valvetrain: SOHC 24-valve
• Compression ratio: 18.5:1
• Injection: Reformed Bosch, inline injection pump with automatic timer, and all-speed mechanical governor
• Power/torque: 173–200 hp (175–203 PS; 129–149 kW), 340–370 lb⋅ft (47–51 kg⋅m)

6HE1

• Displacement: 7.1 L; 434.9 cu in (7,127 cc)
• Bore and stroke: 110 mm × 125 mm (4.3 in × 4.9 in)
• Aspiration: Naturally aspirated or turbocharged
• Valvetrain: Direct injection, SOHC 24-valve
• Compression ratio: 16.9:1
• Injection: Direct injection
• Power/torque: 165–260 hp (167–264 PS; 123–194 kW), 330–560 lb⋅ft (46–77 kg⋅m)

• Isuzu F-Series
• Chevrolet T-Series
• Isuzu H-Series