Article: Driving the Ex-Birkin Blower-4½ Single-Seater Bentley (Page 8 of 8)
Extract from: Motor Sport, by William Boddy, October 1973
Reverting to originality, the radiator is the Welwyn one, but it took a year to retube So is the 45-gallon fuel tank in the tail, but the oil tank behind it had to be fabricated. Incidentally, it was there before the engine was converted to dry-Sump; both tanks have impressive quick-action fillers. The oil tank holds 7 gallons but is filled with 3½ gallons of Castrol GP50. An under-scuttle oil tank used to replenish the sump and feed the blower drip-feeds, of which there were two, for the front and the back bearing, until, on the advice of Amherst Villiers, the front bearing was lubricated by a greaser to cut down oil loss. A new exhaust system had to be made up but the original was there as a pattern, and I need hardly add that every switch is correctly positioned as far as photographs have been able to provide data. The location of the ignition switches, etc., on the n/s cockpit wall looks like a mod. but that is where it was in Birkin's day. Similarly, the instruments are the originals. Russ-Turner lowered the bonnet line to suit the original radiator cowl and Caffyns did what had to be done to the body and re-wired the car, so that it now has a lighting set, etc. However, the mudguards are quickly detachable; as Rusty demonstrated so that we could photograph the Bentley stripped for action.
Birkin had a special gearbox, with centres different from a standard D-type box and with the very noisy wide-toothed "mangle" gears, said to have been fitted because Birkin liked to push the lever quickly about without much in the way of double-declutching! This was obviously of more use on his road-racing Cars. Today a normal D-type gearbox is used. Some of these chamfered-tooth gear wheels are among Rusty's exhibits. He also has the pair of 62-mm. d/d SUs and Birkin's very thin red seat cushion, filled with a bare minimum of strip foam rubber. No wonder he complained of the roughness of Brooklands! Pictures suggest that he must have been about a foot out of the seat in the cramped cockpit at times. . . . This in spite of triple Hartfords and twin B & D shock-absorbers at the rear and triple Hartfords on the front axle—still all fitted.
Some idea of the present capabilities of the Bentley can be gained by Russ-Turner's speeds over the BDC flying kilometre at Ghent, namely 119.2 m.p.h. in 1968 and 123 m.p.h. in 1970. He runs the car on VIP 100-octane from his own garage, getting about 10 m.p.g. on the road, and five m.p.g. in races.
One of the problems has been cracked cylinder blocks. This was not unknown at Brooklands, where with the 12 lb. boost and a 6.0-to-1 c.r. Birkin was placing a lot of stress on blocks with a thickness of only 5 mm. when properly cored. Russ-Turner thinks a 5½-to-1 cr. is about the maximum with petrol but even so has suffered—and new blocks, only an extra millimetre in thickness, cost some £1,000 to cast, and there is no guarantee!
Having had my drive in the car and looked around it, we fell to chatting about its history. Birkin employed quite a large staff to build the blower-4½ team cars at Welwyn. Clive Gallop was Works Manager, Bertie Browning the Foreman. Bill Rockall was the engine and blower man. Fitters and mechanics included the walker Bert Whitlock, Jock Finlayson, John Logan, E. A. Jennings, Edwards, Lawrence and Jackie, etc. Amherst Villiers designed the Roots-type blower and the counter-balanced crankshaft and heavy H-section con.-rods for the racing engines, of which only three such cranks were built. Very early on it is thought that an oil-cooler was used on the single-seater with the wet-sump engine, placed behind a simple dumb-iron fairing. The Powerplus supercharger used for a while was much lower than the Villiers, which seems to have given rise to the suggestion that the big d/d carburetters were used with it. This appears to be erroneous. They were subsequently part of the reinstated Villiers set up. This put their intakes high up inside the radiator cowl and eventually an air scoop to them was fitted on the n/s of the cowl, but right at the end of the Bentley's career and it was never raced with it.
The dry-sump was probably devised to counter oil surge on the Brooklands bankings, when it was realised that higher speeds were about to be attempted. The car was often reported to have retired with "lubrication trouble" and this probably implied that it had run all its bearings. To get a better feed and cooler oil the dry-sump system was needed, and to obviate re-designing the engine with an extra scavenge pump this pump was put on the nose of the blower, in spite of the long run of piping involved between it and the oil tank behind the fuel reservoir. None of the experts who have described the car seems to have realised that it eventually had dry-sump lubrication and it was only when Louis Giron was building up one engine out of the wrecked No. 4 and No. 1 power units for Robertson Roger that the special sump cast for the No. 1 engine, with its off-takes for the piping, made this apparent. It weighs 50 lb. or some 14 lb. more than a normal blower-4½ sump. Why a tail oil tank was fitted in the wet-sump days is not clear to me.
The magnificent rebuild was finally completed on April 29th, 1971, and John Morley was invited to the champagne celebrations. No doubt at this party the amusing story was recalled of how, when the new owner was seeking to get the original Reg. No. for the car, the suspicions of Surrey CC were aroused. They were told the expert to contact was— Rusty Russ-Turner, none other! The chassis number is on the o/s front dumb-iron, whereas W.O. had them stamped on the ns dumb-irons. Which is no doubt why the Log Book quoted the Eng. No. as the chassis No. By the way, Tony Fabian had worked on the Bentley when he was at Caffyns and today he is employed by Russ-Turner and is still working on the car.
Incidentally, my drive on the road in this single-seater was really quite appropriate, because Gallop used to drive it thus from Welwyn to Brooklands, pausing, if a plug oiled-up after going through London, on the hill by Putney Cemetery, near the KLG factory. With rear-wheel brakes only, he must have concentrated pretty hard.
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