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Triumph Stag

Published: 24th Jun 2011 - 0 Comments - Be the first, contribute now!

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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.

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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. 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!

How Did It Drive?

The Stag was never meant to be a sports car like the TR6 although there wasn’t – and isn’t – much in it thanks to the superiority of the Stag’s chassis, itself a derivative of the 2000 saloon which is the thick end of 50 years old.

The Triumph’s soft springing is more aimed at touring and as most Stags were autos suit the car well. The steering also lacks real feel although smaller wheel helps a fair bit. That V8 engine sounds great and possess brisk enough performance as standard for most folk; manual with overdrive is best, especially if the engine is to be dramatically tuned though.

Handling The Power...

Of course, extra power is only part of the picture, you’ll also need to think about upgrading the brakes, suspension and transmission if you’re doing things properly. The fi rst step is to replace the springs and dampers with uprated units along with poly bushing the suspension. This alone not only tightens up the sloppy chassis but also dials out a lot of the famous ‘Triumph twitch’ caused by spline lock up, say experts although the Stag’s soft and restful touring nature will be compromised; it depends what you now want from the car. 

Monarch supplies two braking upgrade kits for the Stag, one using four-pot cast callipers for the front discs, the other using aluminium callipers and ventilated discs. The prices for these front-end kits are £515 and £615 respectively, plus you’ll also want to add the rear disc brake kit, costing £510 although for road use it’s not really needed. However you can also upgrade to a BMW servo with new master cylinder, for a cost of £225, and that’s worthwhile.

BMW bits also come in handy if you want to upgrade the suspension. Monarch can supply complete rear suspensions from the BMW 3 Series, all set up to fi t on to the Stag, for a cost of £1350. One of the advantages of this upgrade is a better camber for the rear suspension. Monarch also sells a BMW differential conversion kit, giving you the complete BMW set up for £1200. 

In terms of transmissions, you’ll be upgrading to the Rover SD1 gearbox if you’re fi tting that car’s V8 engine, and all the bits you’ll need are easily available, either from a specialist or the breakers. If you’re sticking with the original engine, Monarch now supplies a conversion to fourspeed automatic gearbox (from ZF), instead of the standard Borg Warner three-speed slush box. This gives an overdrive-style fourth gear, for better long-speed cruising at lower engine speeds. Apparently it’s also relatively easy to fi t, so could be done on a DIY basis.

With all the performance modifi cations complete, one fi nal piece of advice from Ian at Monarch is to make sure you regularly use the car, especially those still fi tted with the original engine. Stags don’t like sitting around doing nothing… so what more excuse do you need for getting out with the wife and kids and enjoying a Stag party every weekend!

Classic Motoring

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