Vauxhall Slant-4 engine
Overview
Manufacturer	Vauxhall Motors
Production	September 1967 - July 1983[1]
Layout
Configuration	Naturally aspiratedinline-four
Displacement	1,599 cc (97.6 cu in) 1,759 cc (107.3 cu in) 1,979 cc (120.8 cu in) 2,279 cc (139.1 cu in)
Cylinder bore	85.73 mm (3.375 in) 95.25 mm (3.750 in) 97.4 mm (3.83 in)
Piston stroke	69.24 mm (2.726 in) 76.2 mm (3.00 in)
Cylinder block material	Cast iron
Cylinder head material	Cast iron
Valvetrain	SOHC 2 or4 valves x cyl.
Compression ratio	7.3:1, 8.5:1, 9.2:1
Combustion
Fuel system	Carburettor
Fuel type	Petrol
Oil system	Wet sump
Cooling system	Water-cooled
Output
Power output	69.2–135 bhp (51.6–100.7 kW)
Torque output	83–145.5 lb⋅ft (112.5–197.3 N⋅m)
Chronology
Successor	Opel cam-in-head engine

TheVauxhall Slant-4 (orSlant Four) is aninline four-cylinder petrolcarengine manufactured byVauxhall Motors. Unveiled in 1966, it was one of the first productionoverhead camshaft designs to use atiming belt to drive thecamshaft. The Slant-4 block was used as a development mule for theLotus 900 series of engines.^[2] Vauxhall used the engine in a variety of models until production ended in 1983.^[1]

The Slant-4 gets its name from the fact that itscylinders are inclined at an angle of approximately 45° from vertical.^[1] This layout came about because Vauxhall had originally planned to develop a whole family of engines all built on the same production line. There were to be slant-4s and V8s in both petrol and diesel versions, designed under the guidance of Vauxhall's then chief engineer, John Alden. Although a V8 petrol prototype and several 4-cylinder diesel prototypes were built only the 4-cylinder petrol engine made it to series production.

The engine has asingle overhead camshaft driven by a timing belt. The Slant-4 was one of three engines using this method of driving the camshaft released the same year, the others being theFiat Twin Cam engine and thePontiac straight-6 OHC. Prior to 1966, belt-driven camshafts had only appeared in theGlas 1004 series starting in 1962 and in the fewDevin-Panhard cars built starting in 1956. The camshaft operated twovalves per cylinder. An ingenious valve train design incorporating an inclinedsocket head cap screw allowed valve clearances to be adjusted with afeeler gauge and anAllen key. The block andcrossflow head are both ofcast iron. The layout lowers the overall height of the engine, which allowed for moreaerodynamic vehicle bodies to be achieved by lowering thebonnet line. It also means most of the engine is very easy to access for maintenance, with the exception of theexhaust manifold andspark plugs, which are "underneath" the slanted cylinders.

Prototype engines were fitted to theFC Victor, and the engine also appeared in theVauxhall XVRconcept car.^[3] The first production car to use the engine was the 1967FD Victor. The original engine capacities were 1,599 cc (97.6 cu in) and 1,975 cc (120.5 cu in). For the 1972 launch of theFE Victor, the smaller engine was increased to 1,759 cc (107.3 cu in), and the larger to 2,279 cc (139.1 cu in). Blydenstein Racing developed along stroke version with a capacity of 2,600 cc (158.7 cu in) capable of producing almost 250 hp (186 kW). Having been designed to withstand the stresses of diesel compression ignition, the block is immensely strong and able to handle large increases in power without modification. The crank was also designed to be shared with the diesel version, which meant its strength was assured for the petrol version. The larger displacement versions are known for their immensetorque, but also as not very smooth running or high-revving. A fuel-injected version of the 2.3-litre engine was planned for both theHP Firenza andVX4/90. Running prototypes were tested before the project was abandoned due to cost and the impending merger of Vauxhall's design and engineering pool with that of Opel in Germany.

Apart from its use in passenger cars, the engine was also developed formarine applications. It grew popular with tuners due to its great strength, tunability and simplicity. A 2-litre version of the Slant-4 powered the eightCostin Amigos that were built between 1970 and 1972.^[4]: 165 The engine remained in production well into the 1980s for theBedford CF van.

Although arguably more technically advanced, the Slant-4 was considered less reliable than its continental GM counterpart, theOpel CIH (Cam In Head) engine. The Slant-4 was replaced by the CIH in thebadge-engineered VauxhallCavalier Mk.1s from the mid 1970s onward, whilst the Bedford CF van lost the Slant-4 in favour of the CIH when revised in 1983.

It is said that when Vauxhall unveiled its new slant-four engine at the 1966Earls CourtMotor Show its bore centers were exactly the same as those proposed byLotus for their new all-alloy engine. Lotus bossColin Chapman immediately negotiated a deal with Vauxhall to buy some of their cast-iron blocks so that development of Lotus’ own aluminum907 engine could be sped up. For racing the hybrid engines were called LV220 and LV240, with LV standing for Lotus/Vauxhall and the numbers standing for the reported horsepower developed by each version.^[5] Lotus tested the production intent hybrid engine in a Vauxhall Victor and a Vauxhall Viva GT (registration number RAH 713F), as well as in a converted Bedford CF van.

The Lotus 900 series engine block was cast inaluminium alloy instead of iron, which made it considerably lighter than the Slant-4. The Lotus engine also used acylinder head of light alloy that featureddouble overhead camshafts andfour valves per cylinder. With a few modifications the Lotus head could be fitted to the Vauxhall block. Engines with Lotus heads were used in Vauxhall's dealer team race and rally programmes until the late 1970s.^[6]

After experimenting with an 8-valve twin cam cylinder head, Vauxhall began development of a 16-valve, twin cam head for the Slant-4 in the early 1970s. The first test engine, 'Old Number 1', was running by 1973. The cylinder head was similar to the Lotus head in principle, but different in detail; in particular the cam carriers on the Vauxhall engine were angled upwards so that the covers were both horizontal (those on the Lotus engine were equal about the cylinder centreline).

The 16-valve was announced for use in theChevette 2300 HS, which was immediately homologated for racing by the RAC MSA. Vauxhall's own 16-valve head had passed beyond the design stage, but initially was in such short supply that the rally team continued to use the Lotus heads.^[4]: 248 To address the production shortfall Vauxhall approachedCosworth and had them produce the 400 cylinder heads needed for the racing homologation requirements.^{[7]: 83, 84} When the new Vauxhall heads appeared in the Chevette 2300 HST the other teams complained, which led to a homologation scandal. This in turn led to the cars being prevented from starting the 1978Rally of Portugal. As a result, all cars competing in international rallies were forced to use the Vauxhall head.

Lotus raced the hybrid LV engine in twoLotus 62s for a single season.

While Vauxhall'sGeneral Motors parent company had a "no racing" policy, the Slant-4 was campaigned in various cars by the independentDealer Team Vauxhall (DTV) organization. Development of the cars was handled by different groups, including Bill Blydenstein Racing, who ran the rally team and both raced the Lotus-head cars and improved the Vauxhall head to a point where it performed better than the Lotus head. Chris Coburn'sCoburn Improvements also raced under the DTV banner.^[4]: 248

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