About the Dolly Sprint


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A brief history of the Dolomite Sprint.

The Dolomite Sprint was introduced on 19th June 1973 as the first volume 16 Valve car to hit the market. There had been a number of limited edition and low volume 16 valve cars before the Sprint, but the Sprint was designed as a mass market sporting saloon. BL could have introduced a lighter, and maybe faster Toledo TS as a more sporting two door, however, plans to make the Toledo were ditched at the last moment.

The Sprint built upon the highly successful Dolomite saloon with its slant four overhead camshaft engine. The engineers at Triumph had designed the slant four as the base for a number of engine variants. One of those variants was sold to Saab who used the engine in the Saab 99 with a slightly different capacity. The block of the slant four is nearly half that of the Stag V8, and some of the components are shared with the V8. Triumph did supply Saab with a number of V8 engines, not much is known of what Saab did with these. Another variant of the slant four powered the TR7 sports car, with the Sprint's 1998cc capacity, but the 1850's 8 valve head, early 1850's had smaller valves, later 1850's and TR7's shared cylinder heads.

To power a more sporting variant of the Dolomite, (don't forget, the 1850 was and still is no slouch), the engineers designed a 16 valve head where all sixteen valves are operated by a single overhead camshaft. This design led to a design council award for BL.

The camshaft sits directly above the inlet valves and operates those with the same followers and shims as the other variants of the engine and BL engines 1850, TR7, Stag, Rover 2300/2600 and Jaguar 2.9 (single cam). The exhaust valves are operated by rockers that run on a rocker shaft parallel to the camshaft. Each revolution of the camshaft opens the inlet valve, then the exhaust valve. This means that both the inlet and exhaust valves share the same valve timing. Each cylinder has two exhaust valve rockers, a left and right hand rocker for each of the exhaust valves. One side of those left/right rockers is unique to the Sprint, and the other side is shared with the Rover 2300/2600 - you can easily find four new exhaust valve rockers, not so the remaining four.

This clever and simple design allows the two litre Sprint engine to produce 127bhp and spin freely to its 6500rpm limit. The Sprint was originally to be called the Dolomite 135, and a number of these may be in existence. 135bhp was what each engine should have produced, but Triumph was unable to consistently produce engines with 135bhp. However, blue printed standard engines can produce around 150bhp. 

To cope with the 25% power increase, the larger gearbox from the big six saloons, along with the diff was used. The suspension was up-rated with different shock absorbers and the brake disk pad material was changed, along with a larger servo. Although the disks themselves were left the same size, which are puny by today's standards. The rear drums are bigger than the 1850's - as the rear axle is a more substantial item, along with the larger diff. This would have put greater braking ability onto the rear, where its not really required. To get around this problem the BL engineers fitted a rear brake limiting valve. More weight over the rear axle increases the rear brakes pressure, less weight means less pressure.

The Sprint quickly became the four door sporting saloon to own, none of its rivals could offer the same performance for price in a compact four door package.

Production of the Sprint lasted up until 1980, by which time nearly 23,000 Sprints had been produced. Sadly most of them have rotten away by now with only a few hundred registered for use on the road in 2004.

The Sprint had a number of things in it's favor, a relatively large 16 valve engine which gave the car a good power to weight ratio and sporting acceleration, cast alloy wheels (another mass production first) and a roomy well appointed interior. It also had its fair share of things going against it. During its life it suffered from poor quality control, and from 1976 some of the body shells were made from the worst steel know to man (the Italians would have been proud).

The Dolomite Sprint still has a large number of admirers, and recently (2006) was named as the Practical Classic that most people would like to own. These cars are still quick by today's standards, but are no match for the 250bhp hot hatches that are cropping up. A well sorted standard Sprint can easily keep up with most modern traffic, are comfortable and return a good 30mpg average.

With a few minor modifications the Sprint is a also a fun track day car.

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This site was last updated 17-10-06