Holden V8 engine

The Holden V8 engine, also known in some circles colloquially as the Iron Lion (versions from 1969–1985 were also often called the Holden 253 or Holden 308 up until 1974 then Holden 4.2 and Holden 5.0, depending on their capacity), is an overhead valve (OHV) V8 engine that was produced by the Australian General Motors subsidiary, Holden (GMH), between 1969 and 2000.

The engine was initially fitted to the Holden HT series in 1969 and was later utilised in a series of updated versions in the Torana and Commodore ranges. The final iteration, the heavily revised HEC 5000i, was phased out of Holden passenger vehicles with the release of the VT Series II Commodore and the WH Statesman and Caprice in June 1999, both of which featured the 5.7L Gen III V8 imported from the United States. However, the engine remained in production for a little while longer and continued to be available in the Commodore VS Series III utility (which sold alongside the VT sedan and wagon as no similar vehicle was available in that range) until the new generation VU Ute debuted in late 2000.

In addition to being Holden's mainstream performance engine throughout its production run, higher performance versions were fitted to limited-edition vehicles available through Holden Dealer Team Special Vehicles (HDT) and later Holden Special Vehicles (HSV). It was also utilised within limited production vehicles from other manufacturers as well as in kit cars.

The engine has a successful history in various forms of motorsport, most notably in Touring Car racing through the Australian Touring Car Championship and the Bathurst 1000 until 1995, as well as in Formula 5000 and other racing applications such as Sports Sedans.

It can also be found in Australian powerboats fitted with inboard engines, especially those used for water skiing.

In 1964 Ford and Chrysler in the US released V8 versions of their respective Falcon and Valiant models which Holden expected to soon be released in locally assembled or produced versions. In response, in January 1965 the company's engineering division initiated a forward engine program review and concluded that by 1969 a V8 option was a necessity for Holden, with forecasts of 35 per cent of all Holdens sold in 1970 to be V8s, rising to 50 per cent by 1975. Initially six capacities from 237–308 cu in (3,880–5,050 cc) were planned over a 12-year life cycle, but early in the design phase this was reduced to just two, an 'economy' 253ci (4143cc) and an enlarged 'performance' 308ci (5044cc) version, which became known as the 4.2L and 5.0L respectively.

Design targets of a weight of 525 lb (238 kg), which was lighter than equivalent US engines, and a net output of and 161 hp (120 kW) at 4000rpm and 263 lb⋅ft (357 N⋅m) at 2400rpm were set for the 308, which was mechanically identical to the 253 except for a larger bore and bigger pistons, along with heavier counterweights on the crankshaft to compensate for the increased reciprocating mass. Originally an alloy inlet manifold was specified to reduce weight, but this was changed to iron when problems were encountered in the casting process. The exhaust manifolds were also cast iron but the timing case cover remained as an alloy item.

The initial pre-production engine was the 253, which not only met but greatly exceeded the design targets. The complete engine assembly from fan to flywheel and all auxiliaries weighed in at 460 lb, around 12% less than the design target, while net output for the higher compression (9.0:1) version fitted with a 2-barrel carburettor was 185 hp (138 kW) with 262 lb.ft of torque, which matched or exceeded the targets set for the larger 308. The design was also very compact with a width of 22 inches, and was only 80 lb heavier than the 186 cu in (3,050 cc) straight six, but producing over 40% (55 hp (41 kW)) more power than that engine in standard form. The first running engine was delivered in October 1966. Unfortunately, the engine failed after just four days testing from a seized oil pump; however, the problem was found to be caused by swarf residue rather than a fault in the design or the quality of the components. Further testing proved that the engine was smoother and more durable than Holden's six cylinder, no mean feat as the 186 was considered a smooth and reliable engine in its day.