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. It was also installed in the Valiants closely related variants, the Chrysler VIP, the Chrysler by Chrysler & the Valiant Charger.

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 after prototypes were built. This was Chrysler's first thin wall (lightweight) cast iron engine design. 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 245cuin (4.0L) variant was released for the 1970 model year in the VG-model Valiant.

In a major coup for the company, Chrysler Australia's ad agency, the Young & Rubicam Advertising Agency in Adelaide, South Australia, secured the services of British racing driver Stirling Moss to promote the new Hemi-6 4.0L (245cuin) in 1969. The agency managed to fly Moss to Adelaide in secret for the advertising campaign, surprising Chrysler Australia's executives. Young & Rubicam's parent company were also the advertising agents for the Chrysler Corporation in the US.

Engineering and design features

The Hemi-6 is a pushrod overhead valve engine (OHV), the combustion chambers comprise about 35% of the top of the globe, creating a low hemispherical combustion chamber.

The valves are angled apart (splayed) 18 degrees (included angle) along the crankshaft axis, and the intake valves are as large as 1.96in (50mm). The 6 intake and 6 exhaust valves open slightly towards each other and away from the cylinder wall, which results in less "shrouding" of the valves and greater airflow potential. In addition, both valves are slightly inclined across the crankshaft axis, similar to a conventional "wedge" chamber. On the cylinder head the 6 intake and 6 exhaust ports are on the same side of the engine. The rocker arms are mounted on individual studs.

The Australian Hemi engines were designed by a five-man team which included the late Maurice Harcus.

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. Initially, only a single barrel carburettor version was available for Australian built cars but a two barrel version was made especially for the VH and VJ Valiant Ranger XL variants assembled in New Zealand from 1971 to 1975. The two barrel consequently became available in Australia with the VK series update.

Specifications (for 1bbl carbureted variant):

  • Bore × Stroke Size: 3.76in×3.68in (96mm×93mm)
  • Compression ratio: 9.5:1
  • Power: 123kW (167PS; 165hp) at 4600rpm
  • Torque: 318N⋅m (235lb⋅ft) at 1800rpm
  • Intake valve head diameter: 1.845in (46.9mm)
  • Exhaust: 1+1⁄2-inch (38.1mm)

245LC (Low Compression) released in 1977

  • Bore × Stroke Size: 3.76in ×3.68in (96mm ×93mm)
  • Compression ratio: 7.6:1
  • Power: 130hp (97kW) estimate
  • Torque: 180lb⋅ft (244N⋅m) estimate
  • Intake valve head diameter 1.845-inch (46.9mm)
  • Exhaust valve head diameter 1+1⁄2-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 265cuin (4.3L) was introduced in 1971 in the VH. It used a new cylinder block with a bigger bore diameter of 3.91in (99mm)—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 203hp (151kW) at 4600rpm and 262lb⋅ft (355N⋅m) of torque at 2800rpm.

The top-of-the-line performance engine in the E49 Chargers produced 302hp (225kW) at 5600rpm and 320lb⋅ft (434N⋅m) of torque at 4400rpm. The increased power is due mainly to a more aggressive camshaft, high-load valve springs, triple 45mm (1.8in) DCOE sidedraught Weber carburetors, tuned-length exhaust headers and a higher compression ratio of 10.0:1.

Specifications (for 2bbl carbureted variant):

  • Bore × Stroke Size: 3.91in ×3.68in (99mm ×93mm)
  • Compression ratio: 9.5:1
  • Power: 151kW (202hp) at 4600rpm
  • Torque: 355N⋅m (262lb⋅ft) at 2800rpm
  • Intake valve head diameter: 1.96in (49.8mm)
  • Exhaust: 1.6in (40.6mm)

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 VH Valiant. This engine shares the same stroke length as the other engines but has a smaller bore size of 3.52in (89mm) and lower compression ratio of 8.0:1. It ran on regular petrol and produced 104kW (139hp) at 4400rpm and 270N⋅m (199lb⋅ft) of torque at a low 1800rpm.

Specifications:

  • Bore × Stroke Size: 3.52in ×3.68in (89mm ×93mm)
  • Compression ratio: 8.0:1
  • Power: 104kW (139hp) at 4400rpm
  • Torque: 270N⋅m (199lb⋅ft) at 1800rpm
  • Intake valve head diameter: 1.835in (46.6mm)
  • Exhaust valve head diameter: 1+1⁄2in (38.1mm)