TR7 Sprint conversion
This conversion is a fairly simple job, since the 16v engine differs largely only in the head, pistons, timing chain and manifolds. The only major additional part that cannot be sourced form a Dolomite Sprint being the exhaust manifold. This makes it a much simpler conversion than to the TR8 spec. Believe it or not, the most difficult part of the conversion is connecting the engine cooling system to the TR7s cabin heater. The 8 valve engine has a spigot on the plate at the back of the head; whereas the dolly sprint has a plain plate and an 'H' coupling in the pipe-work under the cards. You can either buy a plate with a spigot from Rimmer Bros., or use the sprint pipe-work. This latter option means adapting the sprint ½" to the 7's 5/8" pipe at some point.
You will also have to use the TR7s thermostat cover. In all other respects, the engine is a straight swap. Two important caveats: First, whilst the front pulley and timing plate from the TR7 and Dolly Sprint appear the same, they are not. Hence it is essential to use a set from one or other engine and not mix them up. I would recommend the TR7 pulley and plate, as they're easier to see. Second, the normal U.K. spec TR7 distributor will not fit under the sprint inlet manifold. I have seen an electronic ignition one that looks like it might fit, but I haven't tried it. The problem with the Lucas 44D4 distributor, fitted to the Sprint, is that spares are hard to come by. A replacement rotor arm is available and a remanufactured cap should be available soon. The drive gear is the same as the TR7's and the bushes should represent no problem to a good machinist. It has not been possible to find a genuine engine specification for the TR7 Sprint but it was probably not much different that for the Dolomite sprint. Although the sprint was rated as 127 bhp, the original Dolomite Sprints were listed at 135 bhp and badged as Dolomite 135's, the rating apparently being reduced due to B.L.'s inability to maintain the tolerances required to ensure that all cars met this figure. This would imply that only limited work, the engine ought to yield the full 135 bhp, and that some cars may have yielded this figure when manufactured.
The engine in my factory TR7 Sprint (VVC 697S) remains standard, but has been fully blueprinted and set-up on a rolling road. This car gives 118 bhp at the wheels, which should be approximately 150 at the flywheel. The Dolomite Sprint engine in my fake TR7 Sprint has been blueprinted and has competition exhaust and inlet manifolds and Dellorto 45's. This gives 145 bhp at the wheels and about 190 at the flywheel.
Click here to take a look at my car.
TR7 Sprint x 2 Fake TR7 Sprint DHC Heaps of rust.
The article was originally written by Graham Fountain for the TR Driver magazine in 1989.
Pictures taken without permission from the book 'Triumph TR7 & TR8, owner's & buyer's guide' by James L. Taylor. Published by YesterYear Books (60 Woodville Road, London NW11 9TN).