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The Vanwall Grand Prix engines
Part 6: The 2.6-litre Intercontinental Formula engine


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John Surtees


Vanwall VW14




1961 International Trophy (May 6, 1961)

John Surtees, Vanwall VW14, 1961 International Trophy

By 1960 it was clear that the days of the front-engined Grand Prix car were over and if Vandervell wanted to continue some form of racing utilising his highly developed four-cylinder engine, he would have to produce a rear-engined car. The problem was that in 1961 the Formula 1 regulations were changing and only 1.5-litre un-supercharged engines using pump fuel were permitted. His engine could not be realistically adapted. Although there was some probing research into building a 1.5-litre engine, nothing eventuated.

There had been strong resistance to this proposed new formula by the British constructors and a shortlived alternative designed to utilise the existing supply of 2.5-litre engines was the 3-litre Intercontinental Formula allowing AvGas. Ultimately, this formula only ran until late-1961 before it petered out as support waned.

Vandervell chose to build a rear-engined car to this non-championship formula and to enlarge his engine to suit.

6.1 Engine Development

As stated, the first public appearance of a rear-engined Vanwall was the Lotus 18 chassis fitted with the Vanwall four-cylinder engine in May 1960 on test at Snetterton. Vandervell's decision to build a car to this configuration must have been made quite some time earlier, as his V254 engine could not simply be re-positioned to the rear, as could happen with a Coventry Climax FPF four, for example.

Considerable modifications were required to avoid the injection pump and magneto at the front of the engine intruding too far into the driving compartment and Vandervell also wanted to increase the engine's capacity to capitalise on the 1961 Intercontinental Formula's higher limit. Accordingly, a redesign was carried out and three of the existing V254 engines (V4, V6 and V9) were converted to rear-engine configuration. (Engine V9 was built as a replacement for one of the engines destroyed in 1958.)

All of this occurred in 1960 as the Lotus-Vanwall utilised a modified version of the 2.5-litre engine. Also in 1960, the team at Acton with Colotti's aid designed and built a completely new in-house rear-engined Vanwall, VW14, to take an enlarged 2.6-litre engine to campaign in 1961 in the Intercontinental races.

The enlarged engine was essentially the same as raced before, but the following changes were made:

6.1.1 Increased Engine Capacity

The engine retained the bore at 96mm but the stroke was lengthened from the previous 86mm, to 90mm. This increased the swept volume of the big four to 2,606cc, an increase of 116cc or 4.66%. The stroke-to-bore ratio was increased from 0.8958:1 to 0.9375:1, close to unity.

If the crankpin bearing sizes were maintained, this alteration to the stroke would have required new crankshafts to be made to accommodate the 2mm increase in crank throw. Alternatively, the crankpin journals could have been reground. It is not disclosed which action was chosen.

Also, to accommodate the longer stroke either shorter connecting rods were needed or new pistons with less height above the gudgeon pin were necessary if the existing engine structure was retained. The alternative of retaining the original connecting rods and pistons but increasing the 'deck' height of an already tall engine would be more involved, needing new barrels, water jacket and gear tower. Again it wasn't disclosed which design change was chosen but new parts were made. (For both the May 1960 test and September 1960 entry of the Lotus-Vanwall at Snetterton, an engine of 2.5-litre capacity was used incorporating the modifications detailed in 6.1.3 to 6.1.7 for rear-engine location.)

6.1.2 Cylinder Head

The cylinder head was the same as used on the 2.5-litre engine, as were the valve sizes.

6.1.3 Injection Pump and Magneto Position

The fuel injection pump and magneto had to be moved from the front of the engine to avoid compromising the rear-engine design. They were moved to the right side of the engine, beneath the Amal air-inlet throttle bodies. They were in tandem with the Bosch injection pump first and the B.T.H. magneto behind it, both driven by a modified gear case at the front. This positioning of the injection pump allowed some simplification of the throttle linkage between it and the air-inlet throttles. The spark-plug leads were routed around the rear of the engine from the magneto.

6.1.4 Modified Gear Drive Case

The primary gear drive to the camshafts was modified to have an additional gear drive off to the side to provide drive back to the side-mounted injection pump and the magneto behind it. As the secondary gear case in front of the primary one was now only needed to provide drive to the pulley taking the V-belt drive to the Ceco fuel pump, it is not known whether the case was retained or if it was deleted and drive was taken directly off one of the shafts of the cam gears in the primary case.

6.1.5 Induction

The Amal carburettor bodies used to throttle the air supply were no longer enclosed in a ducted inlet system. Instead, they now protruded out of the engine cover, in the open air.

6.1.6 Exhaust System

The exhaust system was essentially the same as that used on the 1958 engines, suitably adjusted to fit the rear-engine location. The same cylinders were grouped together into two secondary pipes high alongside the engine which then merged into a short tail pipe.

6.1.7 Cooling System

The engine's hot-water off-take fed to a front-mounted radiator and a cylindrical header tank located at the back of the cylinder head. There was also a front-mounted oil radiator cooling both engine and gearbox oil.

6.1.8 Engine Output

The 2.6-litre engine was reported to develop 26bhp more than the 2.5-litre version to give approximately 290bhp at 7,200rpm (equivalent to an impressively high bmep of 200.74 psi).

The torque at peak power rpm was 211.5 lb ft and the engine had very good mid-range torque as well.

At the peak power rpm of 7,200, the mean piston speed was 21.6 m/sec (4,252 ft/min).

6.1.9 Race Performance

Previously,in 1960, while the in-house Vanwall rear-engined car was being developed, Brooks was entered to drive the Lotus-Vanwall in the Lombank Trophy race at Snetterton on 17 September. In practice, the car showed very good speed but suffered engine-valve trouble and was a non-starter. The engine was reported as developing 280bhp and was a modified 2.5-litre rear-engine version, as the race was for F1 cars.

The rear-engined 2.6-litre Vanwall VW14 was finally completed in 1961 and looked very purposeful, built to the usual high standards of workmanship. It was equipped with a 5-speed Type 24 Colotti gearbox/final drive with VP-manufactured internals. It was entered in the Intercontinental Formula's International Trophy race at Silverstone on 6 May, for John Surtees to drive.

Surtees felt the engine was potentially better than the Coventry Climax FPF but found the fuel injection finicky to set up to avoid flat spots. In the race Surtees got up to second place before spinning off and having to pit to clear dirt out of the Vanwall's radiator. He then drove on to finish fifth. This was the last race appearance of a Vanwall.

The 2.6-litre car was entered in one more Intercontinental race, the British Empire Trophy race, again at Silverstone , on 8 July 1961. Vandervell had intended for Surtees to drive but Yeoman Credit, whom Surtees was driving for, refused to release him. Jack Brabham was offered to drive the Vanwall and although he set some promising times in practice, he declined to drive in the race, as he didn't like the handling. So with no other front-line drivers available, Vandervell withdrew his entry and left, finally closing the book on the Vanwall works team.