Triumph Stag

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Which classic cars still have the potential to get up and go? Steve Rowe remembers the cars, the tuners and the tweaks and tells why they’re still hot!

Often favourably compared to the Mercedes SL, the Triumph Stag is one of the most unusual and desirable classic cars, perfect for a sunny Sunday drive. Buy a good one and you’ve got a car that can be used as a daily driver, easily keeping up with modern traffi c. With tuning and modifi cations you can even turn an old Stag into a GTi-beating hunter, but you’ll probably have to compromise on originality and, if you really want a hot car, dispose of the original engine – assuming it’s still there!

The Stag story started back in the mid 1960s, when Harry Webster at Triumph sent a well-used Triumph 2000 to Giovanni Michelotti in Italy, with the aim of producing a show car to help promote the 2000. Harry collected the resulting two-door convertible in February 1966 and set about persuading the management at Triumph to build it.

With the green light eventually given, the next task was to sort the mechanicals. Originally it was thought that Triumph’s 2.5PI unit would be the perfect engine, but, with an eye on the American market, bosses decided that a V8 unit should be fi tted, and had plans afoot to make their own V8 rather than buy-in an existing unit. Triumph was already producing a slant fourcylinder engine, which it was selling to Saab for the 99 model, and engineers planned to effectively join two of these together, to make their own V8.

On paper the finished engine looked very advanced, with a chrome-iron block and an aluminium-alloy head and inlet manifold. The engine was similar in weight to the 2.5PI unit, but produced a ‘claimed’ 145bhp. Two Stromberg carbs sat facing each other and one of the reasons they were chosen over fuel-injection was because of their good antipollution characteristics. For the Californian market, an inlet hot spot and thermostatically-controlled air inlet valve were added to meet emission targets.

Get one now

Good Stags are prized assets but there’s a lot of average, neglected cars out there. The infamous V8 engine soon proved to be unreliable, with corrosion leading to blocked waterways and overheating engines, leading to warped heads. The solution is to use good quality anti-freeze, with rust inhibitor, and keeping an eye on the state of the cooling system and radiator. You’ll probably need to replace or re-core the radiator every 10 years or so to be safe.

The engine’s timing chain also needs replacing every 30,000 miles, something that owners in the 1970s weren’t particularly used to. In addition, water pumps can be problematic and specialists like Monarch Stags (who helped enormously with this feature – 01536 763 778 http://www.monarch-stags. co.uk) now sell kits to fi t a external water pump.

When it comes to tuning the standard engine, opinion varies, with many experts saying that it is best to forget this route and fi t something like a Rover V8 engine instead, since the original unit is too fragile for too much tuning although an honest 170bhp is available and in our minds that’s perfectly adequate for road use!

Hotting one up

If you’re original Triumph engine has been well maintained and is in good shape, then you could consider fitting a stainless manifold (£450 from Monarch) and a Holley four-barrel carb conversion (£550 from Monarch again). The Holley kit is the biggest seller with most owners wanting to squeeze a little extra out of the standard Triumph engine, rather than put in a Rover V8 lump.

Add higher-lift cams and tubular exhaust manifolds and you could be pushing power up but, having said that, Monarch’s Ian Coe reckons that you’ll probably only see about 140bhp on a dyno (similar to what was originally quoted for the standard Stag, showing just how ‘optimistic’ manufacturer’s quoted performance fi gures used to be). Were it possible to fit the 16V head from the Triumph Dolomite Sprint (making a 32-valve V8!) things might get really interesting, but because this head is ‘handed’ there would be problems getting the camchain to fi t on both sides, so this is ruled out although some guys at British Aerospace did make an engine up.

One of the most established Stag soupers is Tony Hart and his Hart Racing Services company (0208 426 1327). It’s wound down now but Tony still builds engines – indeed in his heyday raced a Stag kicking out 280bhp at 8000rpm! You can’t go that wild for road use and Tony admits that a standard engine is pretty restrictive without expensive mods. Headwork is limited – you can fi t TR7 inlet valves for a bit more poke but apart from that it’s a lot of wasted effort. Hart used to have Piper make hairier cams for his engines but the piston tops need to be machined away to stop the valves touching the crown. There’s not much scope for overboring of the unit, 40thou is advised to give an honest 3-litres or a tad more.

Hart says that today an average Stag unit kicks out between 115-120bhp (when new perhaps 135bhp on top fuels) but with his suggest mods can deliver around 170bhp. Electronic ignition is a virtual must. As standard the car was fed by a pair of twin 1.75in Stromberg carbs – fi tting larger 2in ones is diffi cult due to the manifolding he says but he can advise on re jetting the existing ones for a touch more go.

Changing the engine

For those after the ultimate in performance, then the common wisdom is that you’ll need to replace the standard Stag engine with something like a Rover V8. This is the unit that most performance specialists are set up for and kits are available to enable the fi t. For example, the kit from Monarch Stags includes all the engine mounts, rubbers, spacers and the manifold that you’ll need to fit the Rover engine in a Stag. 

Of course, the V8 comes in various capacities, from 3.5 litres to 5.3-litres and there are plenty of specialists who can help you tune this engine once fi tted. The 5.3-litre unit can be pushed up towards a reliable and tractable 350bhp, with modifications like stealth cams and big valve cylinder heads, but you’ll probably spend about £5000 in the process.

It’s also possible to take the 5.0 unit from an old TVR, along with its gearbox, and squeeze them into a Stag – so keep an eye on those scrapyards for a trashed TVR!