Triumph GT6 (1966 to 1973)

Why people buy one

• The 2.0-litre straight six is smooth, torquey and easy to reach under the one-piece tilting bonnet.
• Mechanical parts are shared with the Spitfire, Vitesse and other Triumphs, so most items are easy to find.
• The separate steel chassis makes bodged repairs easier to spot from underneath than on a monocoque car.
• Mk2 and Mk3 cars have revised rear suspension and handle far better than the early swing-axle car.
• The Triumph Sports Six Club was founded around the Herald-chassis cars, including the GT6, and offers strong technical support.

What to weigh up

• Classic & Sports Car says almost every car has had chassis and sill repairs, and many are bodged, so expect to judge the welding rather than find an untouched car.
• The Mk1 kept the Spitfire's swing-axle rear suspension, which can tuck the outside wheel under and cause sudden oversteer.
• Many cars are "parts-bin" builds: engines swapped for 2.5-litre or PI units, rear axles changed and trim mixed, so originality is harder to find than a running car.
• Reproduction Rotoflex couplings are reported not to last as well as originals, so genuine Metalastik units are preferred.
• The cabin can get very warm, and the high gearing works the gearbox hard.
• The Spitfire and the Vitesse are separate cars and are not covered here.

Where they rust

• Sills, which add strength to the body shell; a car with poor sills can sag at the door gaps.
• Floors and the boot floor.
• The one-piece front-hinged bonnet, especially its edges and wheelarches.
• Front chassis rails where they meet the bulkhead, and the bulkhead itself, which gives the body much of its rigidity.
• Chassis rails and the areas around the differential and rear suspension mounts, including the radius-arm mounts on Mk2 and Mk3 cars.
• The fastback roof edges, rear hatch and rear screen seal, where leaks rot the boot floor and rear corners.
• Battery box, door bottoms, A-posts and screen pillars.
• Check the body is bolted to the chassis and has not been welded to it during a past repair.

Mechanical weak spots

• Overheating is a known cause of head gasket failure; white smoke that persists when warm points to the gasket, and a worn thermostat or water pump causes warm running at rest.
• Excessive crankshaft end float is a warning sign of worn thrust washers; blue smoke on the overrun suggests bore or valve guide wear.
• Oil leaks are common, and a brief rattle on start-up is often blamed on the original oil filter, which lacked a non-return valve.
• The four-speed gearbox can have weak synchromesh and layshaft bearing wear (noise in the lower gears, quiet in top); overdrive was an option and faults are often electrical.
• The front trunnions need oiling, not greasing; neglect can seize them and break the vertical link. Check the steering rack for wear and the column for play.
• Rotoflex rubber couplings on Mk2 and most Mk3 cars should be checked for cracks, and early swing-axle cars for worn driveshaft universal joints.

At a Mathewsons viewing

• Check the commission (chassis) number and engine number against the V5C. On UK cars, commission numbers and engine numbers both begin KC on Mk1 and Mk2 cars and KE on Mk3s. Ask whether there is a British Motor Museum Heritage Certificate.
• Look underneath with a torch at the chassis rails, the front rail joints at the bulkhead and the area around the differential, and judge the quality of any welding.
• Lift the carpets, including in the rear load area, and press the floors and sills for soft metal, damp or fresh underseal; check the door gaps for sag.
• Tilt the bonnet forward and look at its lower edges, wheelarches and valance, the radiator and hoses, and for signs of coolant loss or oil leaks.
• On Mk2 and Mk3 cars, look at the rubber Rotoflex couplings on the rear driveshafts for splits, and if staff start the car, listen for knocks and watch for smoke; do not assume it will be started.

Parts, specialists and clubs

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Sources

• Buyer's guide: Triumph GT6 (Classic & Sports Car), 11 June 2026
• Triumph GT6 buyer's guide (Classics World), 17 October 2022
• Triumph GT6: Buyers Guide (Classic Car Hub), 20 April 2026
• Triumph GT6 Buying Guide (Petrolicious), 24 October 2017
• Buyer's guide: Triumph Spitfire (Classic & Sports Car), 10 May 2019
• Restoring the GT6: the body (gt6mk2.com, owner's restoration site), accessed 14 October 2026
• Join the club: Triumph Sports Six Club (Hagerty UK), 19 April 2021