The 'Sprint' engine has its origins in the 1970's SAAB slant 4 (subsequently Turbo-charged). This engine was designed by BLMC (later BL) who used it themselves (in
1972) by installing it in the Triumph Dolomite (1850cc).
In 1973, the Triumph Dolomite Sprint was born. It's cast iron block
consisted of the old 1850cc casting having thicker liners fitted, then rebored to 1998cc. In other words, later 1850cc engines could become 1998cc with a rebore and new pistons - sound familiar TR7 people?
The clever part of the Sprint engine was that the new 16 valve head only needed one camshaft - this won it a British design award. The
camshaft acts directly onto the inlet valves, but uses long fingered rockers to open the exhaust valves. To do this,
each cam lobe is used to open both inlet and exhausts. There is a downside caused by this interaction in that 'manic' cam profiles (specifically overlaps) cannot be used.
The TR7 engine was, in effect, a Sprint engine with the 1850's 8 valve head.
In all, there were about 22,000 Sprint engines made, the last being sold in 1980.
Question: why wasn't the Sprint engine put in the TR7?
Answer: it was!
BL designed the TR7 Sprint (non-US markets only) but due to a long strike at Speke, only 100 were made and sold. The car effectively died with the factory - Speke closed and the TR7 moved to Canley.
Question: why was the Sprint never destined for the US?
Answer: the 8 valve head had integral ports for exhaust recycling, the Sprint had no room for this emission control device.
Question: was the Sprint used elsewhere?
Answer: I like to think that it could have been used in the Triumph Stag (think of 2 TR7 engine siamesed together
to make a 3000cc V8). This engine could have gone to 4 litres and had 32 valves... mmm, nice!
Question: Why not just fit a V8!
Answer: The Sprint conversion is alot simpler and, if the engine is tuned, can give 150bhp which is only 5bhp lower than that of the standard Rover SD1. The Dolomite Sprint race/rally engines reached 200bhp.
TR7 Sprint installation details
Like the TR7 V8, the TR7 Sprint is a safe and sound modification in that the installation design was carried out by BL. All you have to do it copy what they did! Like the TR7 V8 modification,