Vance Navarrette's Journal
Home Page: Vance Navarrette
Beaverton, OR, USA
| Total Posts: 1 | Latest Post: 2018-05-20 |
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This year I decided I am going to build a TR7 Sprint. This is despite having a TR8 which I love to pieces and seeing at least one Sprint for sale, just because I love tinkering.
What is a Sprint? Originally they were all TR7 coupes, with just 60 being built to homologate the engine, and as a project demonstration. The Sprints were plain vanilla TR7s, but with the Triumph Dolomite cylinder head. The Sprint motor used the same slant 4 bottom end as the TR7, but used a SOHC 16 valve head. The intake valves were activated directly by the cam lobes, but the exhaust valves were activated using rocker arms that used the same cam lobes as the intake valves. A clever bit of engineering done on a shoestring budget.
In the 1970s, 16 valve engines were a rarity in a mass produced vehicle, mostly in Italian cars made in small numbers, and in high end exotics. In a budget sports car, they were unheard of. Using the Sprint head takes the TR7 2.0 slant four from 95HP in US spec to 135HP or a bit more.
Sadly, the TR7 Sprint never went into production, with the 60 prototypes sold to employees and the program shelved.
But the Dolomite was made in reasonable numbers, and used parts are readily available on eBay UK, despite never being imported into the US.
To date, I have acquired the cylinder head, valve cover, intake manifold, front timing cover, distributor and Dolomite air box.
The stock TR7 distributor will not clear the Sprint intake manifold, although I suspect with the right distributor cap it would work just fine.
At this point I still need to acquire a camshaft, pistons (9.5:1 CR with valve reliefs) rings, wrist pins, and an exhaust manifold. I have yet to select a car to convert, but I plan on doing that at the end of the summer when cars are CHEAP.
Complicating things is that I get emissions tested where I live, so the car must be able to pass a sniffer test. This means I will need a CAT and air injection at least, and perhaps EGR.
Stay tuned for updates as I throw money into a bottomless pit while I build a car that no one ever heard of, and probably no one wants.
What is a Sprint? Originally they were all TR7 coupes, with just 60 being built to homologate the engine, and as a project demonstration. The Sprints were plain vanilla TR7s, but with the Triumph Dolomite cylinder head. The Sprint motor used the same slant 4 bottom end as the TR7, but used a SOHC 16 valve head. The intake valves were activated directly by the cam lobes, but the exhaust valves were activated using rocker arms that used the same cam lobes as the intake valves. A clever bit of engineering done on a shoestring budget.
In the 1970s, 16 valve engines were a rarity in a mass produced vehicle, mostly in Italian cars made in small numbers, and in high end exotics. In a budget sports car, they were unheard of. Using the Sprint head takes the TR7 2.0 slant four from 95HP in US spec to 135HP or a bit more.
Sadly, the TR7 Sprint never went into production, with the 60 prototypes sold to employees and the program shelved.
But the Dolomite was made in reasonable numbers, and used parts are readily available on eBay UK, despite never being imported into the US.
To date, I have acquired the cylinder head, valve cover, intake manifold, front timing cover, distributor and Dolomite air box.
The stock TR7 distributor will not clear the Sprint intake manifold, although I suspect with the right distributor cap it would work just fine.
At this point I still need to acquire a camshaft, pistons (9.5:1 CR with valve reliefs) rings, wrist pins, and an exhaust manifold. I have yet to select a car to convert, but I plan on doing that at the end of the summer when cars are CHEAP.
Complicating things is that I get emissions tested where I live, so the car must be able to pass a sniffer test. This means I will need a CAT and air injection at least, and perhaps EGR.
Stay tuned for updates as I throw money into a bottomless pit while I build a car that no one ever heard of, and probably no one wants.
Dolomite Sprint head, showing exhaust rockers
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