Sixteen-valve Dolomite Sprint from Triumph
Lord Stokes recently intimated that part of the Triumph Motor Co.’s role within British Leyland in the future would be to produce small, but refined, four-seater saloons in the luxury high-performance category to compete with similar types of cars produced so successfully on the Continent. The first result of this policy and a good portent for future products from Canley is the 116-m.p.h., 16-valve Triumph Dolomite Sprint, introduced to the British market in mid-June.
Triumph have taken the popular Dolomite’s body, luxury interior and suspension, and given it a 1,998-c.c., 127-b.h.p. net, 16-valve version of the 45-degree inclined four-cylinder engine originally developed by them for Saab and latterly used in 1,854-c.c., 8-valve, 91-b.h.p. net trim for the ordinary Dolomite. It endows the small, but heavy saloon, weighing one ton at the kerb, with performance on a par with, and in some ranges superior to, the Escort RS 1600.
The new engine has been an open secret for some time, receiving wide publicity in Brian Culcheth’s rally Dolomite. Its most intriguing feature is the method of valve operation, which disdains twin overhead camshafts to operate the 4-valves-per-cylinder in favour of a single overhead camshaft activating only the inlet valves directly. The exhaust valves are operated by eight rockers pivoting on a shaft mounted midway between the two lines of valves, the rockers bearing on the same eight cams of the camshaft as the inlet valves. A duplex chain is used to drive the camshaft as on the 8-valve engine and the cylinder head is constructed in gravity die-cast aluminium with iron valve seat inserts. An alloy cam cover is designed to help with sound deadening.
The block retains the same 78-mm. stroke as the 1,854-c.c. unit, a very over-square configuration being achieved by opening out the bores from 87 mm. to 90.3 mm. While the block otherwise remains basically the same as the normal Dolomite’s, bottom end lubrication has been improved by cross-drilling the big-ends of the forged steel, 5-main bearing crankshaft. Eight bolts secure the cast iron flywheel to cope with the extra inertia torque.
Triumph have referred to one of British Leyland’s own companies for the carburetters, twin SU HS6 1-3/4 in. in place of the Dolomite’s Strombergs, mounted on fully-flowed, branched, water-heated aluminium manifolds. The cast-iron exhaust manifold feeds into a twin aluminised system as far as the gearbox, where it joins briefly before parting again into two silencers and tail pipes.
Mechanical improvements go much further than the engine, however. A new gearbox is fitted with what are basically the 2.5 PI/TR6 innards to afford much greater strength, while a Laycock de Normanville “J”-type overdrive, already introduced as an option on the standard Dolomite, will shortly be available on the Sprint for an additional £71.50. The hydraulically-operated diaphragm clutch remains the same size at 8-1/2 in., the two-piece propshaft now carries a constant velocity joint in the centre bearing as well as universal joints, while the axle, we are told, has been improved to cater for the extra power and utilises a 3.45-to-1 final drive in place of a 3.63 to 1.
Suspension remains identical in design to the Dolomite, but front spring and damper rates and rear damper rates have been uprated. The same front and rear anti-roll bars have been retained.
A further roadholding improvement is effected by the fitment of 5-1/2J Dunlop alloy wheels designed specially for this car and fitted with 175/70 HR 13 Dunlop SP Sports.
The Girling braking department has also been the subject of improvement, rear drums being increased in size from 8 in. x 1-1/2 in. to 9 in. x 1-3/4 in. (8-3/4 in. front discs remain the same), an 8-in. servo is fitted in place of a 7-in, one and a load sensitive distribution valve included.
A frequently voiced complaint about the standard Dolomite has been that it looks too much like the rest of Triumph’s small car range. There is no mistaking the Sprint, however, which is distinguished by the handsome wheels (we’ve always thought the Dolomite’s wheels look far too spindly) and the same range of bright colours used on the sports cars, complete with neat, contrasting flashes down the waistline and a vinyl roof. The first 2,000 are being produced in mimosa yellow with black coachline.
Another very consequential external difference is a spoiler below the front apron. Acquaintances at Triumph tell us that this is far from being a fancy gimmick: while the standard Dolomite remains perfectly stable when pushed to over 100 m.p.h., the Sprint, with higher cruising and cornering speeds, showed a marked tendency for departing from the tarmac before the addition of the spoiler.
Other modifications include a viscous-driven cooling fan and the four headlights uprated to 37.5/60 watt outer lights and 75 watt inner lights, while the leather-rimmed steering wheel, in common with the Dolomite, is now smaller.
A brief drive in the Sprint in the Geneva area a couple of months ago left a lasting impression of what a splendid concept this extremely rapid car is. We’ve always enjoyed our sessions with Escort RSs, but find them rather spartan, while the BDA engine is noisy and somewhat temperamental for high-mileage road use. The Sprint combines the Escort handling-and performance delights with an extraordinarily high standard of appointment, comfort and relative silence. Perhaps the most staggering thing is the torque and flexibility, which allowed us to potter through French-Swiss border towns at 1,000 r.p.m. in top gear, even up inclines, and accelerate up to a maximum speed on the autoroute of nearer 120 m.p.h. than Triumph’s conservative 116-m.p.h. claim. Even then it was necessary to lift off to avoid the tachometer needle disappearing into the red beyond 6,500 r.p.m. down slight gradients, representing in excess of 120 m.p.h. If the prototype Sprint without the spoiler was as frightening at high speed as we are informed, then the spoiler on the production car is extraordinarily effective, for in spite of some wander occasioned by very high side winds, there was no tendency for the steering to go light or stability to be reduced.
The original Dolomite gearbox had a rather too high 1st gear even with the lower final-drive ratio. The Sprint’s higher final-drive ratio combined with lower 1st gear gives roughly the same overall gearing and maximum speed of 41 m.p.h., but the 16-valves’ torque copes easily with it. However, the other ratios in the box weren’t so satisfying as the close ones of the original Dolomite, giving maximum speeds of 58 m.p.h. in 2nd and 89 in 3rd. The box was pleasant to use, if not so good as an Escort’s.
Over winding roads the Sprint handled excellently with a safe degree of initial understeer, progressing to well-balanced neutrality with the ability to hang out the tail round tighter corners. Axle location could have stood a little improvement and a limited-slip differential would have been appreciated for increased traction, it being all too easy to spin the inner wheel. Steering feel and response was good, while the brakes were outstanding.
The stiffer damping and springing had done nothing to make the ride inferior to the Dolomite’s–in fact the very opposite, for we always felt the Dolomite was under-damped. The general degree of comfort in the fully-adjustable, Bri-Nylon seats, we feel to be superlative in a car of this size, and while the amount of woodwork is a matter of personal like or dislike, it gives an overall air of expensive quality. Instruments include a tachometer, 140-m.p.h. speedometer with trip, clock, fuel gauge, water-temperature gauge, battery condition indicator, but, strangely no oil-pressure gauge.
Unlike the Escort RS, mechanical noise was non-existent, progressive high revs creating little more than a plaintive induction buzz from the well-silenced SUs and very little exhaust noise.
A tuning friend, who is currently working on a Sprint head for an autocross car, is most impressed by the design, which has inlet valves the same size as the racing Ford BDG engine, inlet ports only fractionally smaller and finely machined valve throats, while the pent-roof combustion chamber with Champion BN7Y plugs in their centres can be little improved. His only doubts are that the cam and rocker-valve operation might prove unsuitable for ultra-high revs if the engine was to be highly tuned for competition use. Some idea of the efficiency of the cylinder head can be gained from Triumph’s claimed fuel consumption figures, which quite staggeringly improve on those of the standard Dolomite, 32 m.p.g. being claimed at a steady 70 m.p.h.
Claimed performance figures include 0-60 m.p.h in 9.2 sec., 0-80 m.p.h. in 16.4 sec. and 0-100 m.p.h. in 28.5 sec. While standing start figures are fractionally down on the BMW 2002 Tii and Alfa Romeo GTV, acceleration in the gears is said to be better in many of the ranges. This sort of performance from a saloon car of such compact dimensions and comfort makes the Dolomite Sprint remarkable value for the money compared with its continental competitors, at £1,739.84, cheaper by £22 than the Escort RS 1600. One can only hope that Triumph can improve their manufacturing standards to the level of BMW, for if the same standards are maintained which applied to the troublesome new editorial TR6, British Leyland will lose out on a potential world-beater. – C.R.