Triumph GT6

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Do you drive this great classic or are thinking of buying one? Here’s how to ensure that you get the best out of your car for years to come

The Triumph GT6 may be little more than a Spitfire on steroids but it makes for a swift and smooth GT that’s also a DIYer’s dream thanks to its Meccanolike construction and amazing access to the engine and front suspension care of that forward-hinged front end. Mechanically, the simple design is a mix of Vitesse and Spitfire meaning good specialist support and parts availability. The GT6 was dubbed a mini E-type – here’s how to make yours go like one!

Bottom End

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There’s a bit of stretch in the straight six engine to 2.7-litres once stroked to 2.5 but it’s dear and a luxury for most although provides good torque. The 2000 engine can be taken to 2.5 using its crank etc, but needs TR6 head for best effect, fitted for ’69 and you need to watch the compression ratios if you stick with existing one.

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Engines are durable, but can suffer from excess crank end float. Up to 12thou means a simple replacement of the thrust washers might effect a cure. Over 50thou and the thrust washers fall out, and that’s very expensive as a rebuild and even a new block is required. Oil pressure should be quite high; if it drops as low as 10psi at idle or the needle becomes erratic, the crank is probably pretty worn.

Front Suspension

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Uprated springs and dampers along with better (thicker) anti-roll bar although tweaks MUST be matched to rear end improvements; speak to a specialist for advice. Rimmers lists an Upper Suspension Overhaul under £30 plus a KSX spring/ damper upgrade which are ride and height adjustable at just over £300. Jigsaw Racing Services markets a new harder bush kit for £189.

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Front trunnion wear is the biggest worry as seizure can lead to a wheel falling off in extreme circumstances. Regular lubrication is vital; EP90 oil is the recommended lube although most use grease as it’s easier to use with a gun. New trunnions cost under £40 per side from www. rimmerbros.co.uk and worth doing before contemplating any mods. Rattles from steering column bushes not unknown but it’s a simple fix.

Chasis

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You can make a Spitfire 6 by either a re-engine of a Spitfire or dropping its body on a GT6 platform but it’s not as easy as it sounds. You can make a GT6 look sportier by fitting a fibreglass Le Mans bonnet, sold by Jigsaw Racing Services, featuring covered headlamps. At £725 it’s a good mod as standard bonnet does rust and are dear to replace anyway.

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The chassis can rot badly; rails, suspension pickup points (especially the rear) and outriggers although part replacements are available as are complete new frames, although costing well over £1000 you need to weigh up if a car is worth saving. A common rust spot is on the roof just above the windscreen. There’s no new bodyshells available anymore.

Transmission

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You can fit the Ford Sierra Type 9 five-speeder although this may be unnecessary say experts as the overdrive works agreeably well, provides six ratios and can be uprated with stronger clutches and springs plus higher operating pressure for more ‘immediate’ engagement. Stag ’box can be used and has different ratios while overdrive gearing was revised on all ’boxes for 1975.

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Rear U/Js work loose and lead to vibrations and need regular checks. Sloppy, chattering gear lever simply needs new bushes for under £15. Overdrive faults are usually electrical not mechanical; some fit later gear-mounted switch for convenience. Gearboxes can lose their synchro quickly and give layshaft trouble when worn.

Engine Output

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Almost 200bhp is achievable but realistically 175-180bhp for road use is more sensible. Upping a standard 2000 engine to 2.5 is worth up to 20bhp on its own. Better breathing with induction and exhaust mods is first step before substituting head and cam. Weber DCOE carbs ultimate but pricey; if standard set up is okay it can cope well enough with fairly major engine tuning say up to 140bhp after recalibration.

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Electronic ignition is worth installing as is an uprated rad, especially on tuned engines. An oil cooler may be required and we’d fit a later spin-on filter conversion to aid start up flow. If you need a new engine, after 1974 all saloon ones were uprated and best of the lot was the one taken from the 2500S (the replacement for the 2.5PI) which posted just under 110bhp (net).

Brakes

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GT6 boasts bigger brakes over the Spitfire and if in good order the stock disc/drum set up can cope with more speed using just new sports discs and harder pads; try EBC for starters. Quiller Triumph has an upgrade kit boasting vented discs for £136. Ford Capri 2.8i discs fit (if you can source them) or you can install four pot conversions (try Canley Classics) but you may need to go to 14inch wheels as a result. Rear discs can be grafted on but only needed for track work.

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Brakes are utterly conventional and have no real quirks if serviced correctly. Magnificent steering lock scrubs the front tyres if regularly employed. If wider tyres and rims are fitted check that they do not rub the flexible brake hoses and lead to failure; not unknown.

Wheels & Tyres

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You can opt for traditional wire wheels or alloy rims but Triumph specialists Jigsaw has something different; Le Mans rims. Made by Compormotive, they are a 5.5J alloy replica in Old English White and cost just under £700 a set.

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Don’t over-tyre the car; 175/185 section radials are plenty and watch for tyre scrub on full lock. And consult a specialist concerning pressures as it makes a difference.

Interior

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A superior wooden dash and the option of leather covering for the seats can be dialled in. A good many came with a sunroof (glass portholes look terrible on a GT6) and you can still have one fitted by a specialist. US cars had air con provision and can be adapted.

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Bonnet prone to rattling but that’s adjustment, worn side catches. Sunroofs were very popular but obtaining replacement parts can be difficult so you may have to have a whole new one installed. Fibreglass transmission tunnels are available and save weight.

Rear Suspension

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Various aftermarket tweaks were devised over the decades but Mk4 Spitfire design is now regarded as the best modification to a GT6 along with better dampers – GAZ come recommended. Uprated springs are available and there’s an American full-on IRS set up at some £1200.

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Rear wheel bearings must be regularly greased. Clapped out universal joints result in vibrations and spoil handling as do myriad of bushes that were used; go polybush for tighter feel, longer life. Rear end is sensitive to its ‘toe out’ geometry setting; odd tyre wear is one clue to maladjustment but it can be also due to a worn transverse rear leaf spring.

Servicing Data

ENGINE OIL: 20W/50/60 8pts
GEARBOX: EP90 1.5pts (with o/d)
REAR AXLE: EP90 1pt
COOLING SYSTEM: 11pts
SPARK PLUGS: N9Y (NGK BPS6S) or equiv 0.025in
C.B. POINTS GAP: 0.014-0.016in
TIMING: 10 degrees BTDC
VALVE CLEARANCES: in/ex 0.010in (set hot)

And Another Thing…

What about a GT8? Slotting in the evergreen Rover V8 (or perhaps the Stag unit) has been done on Spitfires so there’s no reason why a GT6 can’t be as accommodating although a large ungainly bonnet bulge will have to be grafted on. Perhaps a straight six taken from a BMW or Toyota or Lexus may fit with some ingenuity. Want an auto? Canley Classics apparently converted a Herald using a Triumph 2000 donor so it’s quite doable.