Chrysler Hemi-6 Engine

The Chrysler Hemi-6 engine is a family of inline six cylinder petrol engines produced by Chrysler Australia in three piston displacements and multiple configurations. Hemi-6 engines were installed in Australian-market Chrysler Valiants from 1970 through 1981.

Development and release

Chrysler Corporation in the US had been working since 1966 on an inline 6-cylinder engine, called the D-engine, to replace the Slant 6 (G-engine) in Dodge trucks, but abandoned the effort. Chrysler Australia wanted a new six-cylinder engine for use in the Australian Chrysler Valiant, and so Chrysler USA sent a prototype engine to Chrysler Australia's engineers to continue developing the D-engine. The first 245 cu in (4.0 L) variant was released for the 1970 model year in the VG-model Valiant.

Engineering and design features

The Hemi-6 is a pushrod O.H.V. (overhead valve) engine, with combustion chambers comprising about 35% of the top of the globe. This creates what is known as a low hemispherical shaped chamber. Although the Hemi-6 does not contain truly hemispherical combustion chambers, the "Hemi" moniker was used primarily for its marketing cachet based on the reputation of Chrysler's 1950s-1970s (true) Hemi V8 engines.

The Hemi-6 valves are 18 degrees (included angle) along the crankshaft axis opposed valves, with intake valves as large as 1.96". The 6 intake and 6 exhaust valves open toward each other, and into the center of the combustion chamber. In addition, both valves are slightly inclined across the crankshaft axis (similar to a conventional "wedge" chamber). The cylinder head is a non-crossflow design, meaning the 6 intake and 6 exhaust ports are on the same (left, Australian and British passenger's side) of the engine.

Unlike Chrysler's contemporaneous hemi V8 engines, the Hemi-6's rocker arms are mounted on individual studs (similar to the Chevrolet "big block" V8), rather than on 2 separate rocker shafts as in all 1951-58 Dodge, DeSoto and Chrysler "Firepower" and 1964-* RB hemi v8s.

All Hemi-6s share a robust crankshaft supported by seven main bearings, and this family of engines quickly developed a reputation for excellent performance, economy, and durability.

Versions and variants

245 cu in (4.0 L)

Chrysler "hemi" 245 prototype, on display at the National motor museum, Birdwood, South Australia

The 245 was the initial version of the Hemi-6 engine. It was first used in the 1970 VG-model Valiant, and was available clear through to the final CM model of 1981.

Specifications (for 1bbl carbureted variant):

• Bore Size: 3.76 in (95.5 mm)
• Stroke: 3.68 in (93.5 mm)
• Compression ratio: 9.5:1
• Power: 165 hp (123 kW) @ 4600 rpm
• Torque: 235 ft·lbf (318 Nm) @ 1800 rpm
• Intake valve head diameter: 1.845 in (46.9 mm)
• Exhaust: 1.500 in (38.1 mm)

245LC (Low Compression) released in 1977

• Bore Size: 3.76 (95.5mm)
• Stroke: 3.68 (93.5mm)
• Compression ratio: 7.6:1
• Power: 130 hp (97 kW) estimate
• Torque: 180 ft·lbf (240 N·m) estimate
• Intake valve head diameter 1.845 inch (46.9mm)
• Exhaust valve head diameter 1.500 inch (38.1mm)

265 cu in (4.3 L)

Chrysler Hemi 265ci 6 cylinder hemispherical combustion chambers with large intake and exhaust valves (removed) and big square ports

The 265 was introduced in 1971 in the VH. It used a new cylinder block with a bigger bore diameter of 3.91 in (99.3 mm)—the same as many of the Chrysler small-block V8s—and a new cylinder head, having slightly more hemispherical shaped combustion chambers with larger valves.

The standard version of the 265 produced 203 hp (151 kW) @ 4600 rpm and 262 lb·ft (355 N·m) of torque @ 2800 rpm.

The top of the line performance engine in the E49 Chargers produced 302 hp (225 kW) @ 5600 rpm and 320 lb·ft (434 N·m) of torque @ 4400 rpm. The increased power is due mainly to a more aggressive camshaft, high-load valve springs, triple 45 mm DCOE Weber sidedraught carburetors, tuned-length exhaust headers and a higher compression ratio of 10.0:1.

Specifications (for 2bbl carbureted variant):

• Bore Size: 3.91 in (99.3 mm)
• Stroke: 3.68 in (93.5 mm)
• Compression ratio: 9.5:1
• Power: 203 hp (151 kW) @ 4600 rpm
• Torque: 262 ft·lbf (355 Nm) @ 2800 rpm
• Intake valve head diameter: 1.96 in (49.8 mm)
• Exhaust: 1.60 in (40.6 mm)

215 cu in (3.5 L)

This economy-orientated version of the Hemi 6 was released as a running change in early 1971 as the base model engine in the VG Valiant. This engine shares the same stroke length as the other engines but has a smaller bore size of 3.52 inches (89 mm) and lower compression ratio of 8.0:1. It ran on regular petrol and produced 140 hp (104 kW) at 4400 rpm and 200 lb·ft (270 N·m) of torque at a low 1800 rpm.

Specifications:

• Bore Size: 3.52 in (89.4 mm)
• Stroke: 3.68 in (93.5 mm)
• Compression ratio: 8.0:1
• Power: 140 hp (104 kW) @ [4400] rpm
• Torque: 200 ft·lbf (270 Nm) @ [1800] rpm
• Intake valve head diameter: 1.835 in (46.6 mm)
• Exhaust valve head diameter: 1.500 in (38.1 mm)