The Holden straight-six motor is a straight-six engine produced by General Motors–Holden's in Australia between 1948 and 1986. Initially dubbed the Grey motor alluding to the colour of the cylinder block, later iterations came in the form of a Red, Blue, Black and the four-cylinder Starfire engine. These engines were fitted to all Australian-designed Holdens of the same years, and the four-cylinder Starfire notably found its way into the Toyota Corona (XT130). The grey motor is a different engine to the latter ones. The Red, Blue, Black and even the Starfire are all inter-related with many common parts and castings.
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The Grey motor built between 1948 and 1962, earned its name as the engine block was painted grey. This overhead valve engine was first fitted to the Holden 48-215 and mated to a three-speed manual transmission. A three-speed GM Roto-Hydramatic 240 automatic transmission was optionally fitted in the latter EK and EJ series. The engine was based on a Buick pre-World War II design, and saw only minor changes throughout its 15-year life.
It displaced 132.5 cubic inches (2.2 L) in its original form, and was bored out to 138 cubic inches (2.3 L) when the FB series was introduced in 1960. It made 60 brake horsepower (45 kW) at 5000 rpm, providing superior performance than competing four-cylinder Austin, Morris, Vauxhall and Ford of Britain vehicles. Due to the low compression ratio (7.5:1) they were able to revolve quite fast and effortlessly. Due to their sheer ubiquity, they were popular for racing, and were fitted to many open-wheelers, as well as racing Holdens. With the motors' low-end torque, they also found their way into boats and machinery such as forklift trucks.
This engine ran a seven-port non-crossflow cast iron cylinder head. There were three siamese (shared) inlet ports for cylinders 1-2, 3-4 and 5-6, two individual exhaust ports for cylinders 1 and 6, and two siamese exhaust ports for cylinders 2-3 and 4-5 in a layout on one side of the head casting. The inlets were fed by a single barrel Stromberg carburettor in common and fitted with a traditional points distributor and ignition coil. The ignition system was six volts to match the 48-215 and FJ's six volt negative ground system, as was the starter engine. The earliest grey motors (approximately 100,000) were fitted with Delco-Remy accessories, although Lucas and Bosch equivalents throughout the motor’s lifetime replaced these.
The very first production grey motor (1948) was number 1001, and they continued in a single sequence until July 1956, when the prefix "L" was introduced.[1] The change affected all engines numbered L283373 and above, signifying the 12 volt negative ground engines as fitted to the all new FE model. The prefix "U" was introduced for motors with the original electricals as fitted to the run-on FJ utility and panel van models, which ended in February and May 1957 respectively. The change was effective from engine U283384.[1] The prefix "B" was introduced and the number sequence reset with the introduction of the 138 cubic inches (2.3 L) displacement engine, and ultimately this was replaced by a "J" prefix for motors fitted to EJ vehicles in 1962.
| Engine | Displacement | Compression | Power | Torque | ||
|---|---|---|---|---|---|---|
| bhp | kW | ft·lb | N·m | |||
| 2.84 L Red I6 | 173 cu in | Low | 112 | 84 | 160 | 220 |
| High | 118 | 88 | 168 | 228 | ||
| 3.3 L Red I6 | 202 cu in | Low | 129 | 96 | 190 | 260 |
| High | 135 | 101 | 194 | 263 | ||
Superseding the Grey motor, the Red motor was manufactured between 1963 and 1980. Denoted by the cylinder block painted red, the engine debuted in the Holden EH in capacities of 149 cubic inches (2.44 L) and 179 cubic inches (2.93 L) (or HP) producing 100 brake horsepower (75 kW) and 115 brake horsepower (86 kW) respectively. This was a power increase of 33 per cent and 53 per cent over the previous motor.[2]
Red six-cylinder engines manufactured after October 1964 had the cubic inch capacity of the engine cast in raised numbers on the side of the block behind the generator/alternator location. Red engines manufactured prior to October 1964 had either no numbers cast (meaning that it was a 149 cubic inch engine) or the letters "HP" cast (meaning that it was a 179 cubic inch engine). All Red engines manufactured prior to April 1967 (including 149, 179, 161 and 186 engines) had forged steel crankshafts.
The Blue specification debuted in the 1980 VC Commodore.[3]
The blue motor was a development of the earlier red engine, and incorporated several improvements. The biggest of these changes was the complete redesign of the cylinder head; this was now a 12 port design with individual ports for each cylinder. The crankshaft for the 3.3-litre engine now had counterweights on each throw, and stronger connecting rods were used. A two-barrel Varajet carburetor was standard, as was a dual outlet exhaust manifold and a Bosch HEI distributor. It was made in 3.3- and 2.85-litre versions.
The Black specification was introduced in the 1984 VK Commodore. In the VL series of 1986, Holden ceased the tradition of employing Australian-made and designed six-cylinder engines, instead opting for the Nissan RB30 engine. This came because pending emission standards and the requirement for unleaded fuel made it difficult to re-engineer the engine.[4]
The black engine was produced in 3.3-litre form only, and in carbureted and fuel-injected versions. The carbureted engine was almost identical to the previous blue engine, the main difference being in the use of computer controlled spark timing (EST) The ports are slightly wider spaced meaning the manifolds will not simply interchange. The Bosch-injected version used a long-runner intake manifold and a conventional HEI ignition. It also had slightly different cylinder head intake ports for improved breathing.
This 1.9-litre (1,892 cc) powerplant, known as the Starfire engine, was effectively Holden's existing 2.85-litre 173 cu in straight-six with two cylinders removed.[3] Designed and built in Australia to satisfy local content rules, it first appeared in 1978 during the UC Sunbird's production run, replacing the Opel 1.9L cam-in-head unit used in LH, LX and earlier UC Torana/Sunbird 4-cylinder models.
Peak power output for the Starfire was 58 kilowatts (78 hp), with a 17.5 second acceleration time from 0-100 kilometres (0–62 mi) in the VC Commodore.[5] This variant's performance meant the need to push the engine hard leading to fuel consumption similar to the straight-sixes. Due to this, it was often nicknamed as Misfire or Backfire. This engine was replaced in the Australian market by the Camira's OHC Camtech unit, however it continued until 1986 in New Zealand, where it was used to power 4-cylinder versions of the VK Commodore.