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.
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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.
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.
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):
245LC (Low Compression) released in 1977
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):
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: