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Posted by Glenn Rowswell on 14th May 2018

The TR6 had the longest production run of all the TRs and remains one of the most affordable of the traditional cars…

The TR6 is another of those products of the British motor industry which enjoyed a far longer lifespan than anyone could have reasonably expected. Delays to its replacement (the TR7) can partly be blamed of course, but in reality the TR6 can trace the essence of its design right back to the original TR2 in 1953.

The chassis of that original TR was modified in 1965 to accommodate the independent rear suspension developed for the TR4a, but was essentially the same basic design: two main longitudinal rails with X-shaped cross bracing providing additional rigidity, connected in the centre by a box section and with outriggers at the sides for body support.

Triumph squeezed a good lifespan out of its TR bodyshell design too: the TR6 was created by Karmann merely by restyling the nose and tail of the predecessor, the TR5, which shared its Michelotti-penned style with the TR4. Parts sharing at its finest here!

The TR6’s trademark six-cylinder engine had also put in a good showing previously, having first appeared in 1960 in the Vanguard Six and its first sports car use being in 1967 with the TR5. Its origins went back further though, since the six-pot engine was essentially one-and-a-half of Triumph’s four-cylinder engine, which also saw service in the Ferguson tractor.

The Triumph TR6 was first launched in 1969 in 150bhp form, running Lucas fuel injection. For 1970 the windscreen pillars became black instead of body-coloured, while the disc wheels were changed from a 12-hole to a 15-hole design, while the Rostyle rims were no longer offered. By 1971, the engine cooling fan was changed from a seven to an eight-blade design and in 1972 the cars gained a steering lock.

The first major change came in 1972 when the engine spec was revised to provide smoother low-speed running. This involved revised camshaft timing, with the trade-off being a drop to 125bhp. For 1973, the TR6 received a black plastic chin spoiler, the wiper arms became matt black instead of chrome and the air intake became a black plastic item, while a stainless strip was added at the top and bottom of the grille. Inside, head rests were now standard, while the style of interior trim was changed, as was the switchgear and instrumentation.

The wire wheel option was discontinued in 1973 and overdrive became standard in 1974, together with the previously optional tonneau cover. After more than 91,000 examples were produced, production ended on February 7, 1975 (just as the TR7 came on stream).

Triumph TR6 Buyers Guide

North American market carburettor cars were given a CC prefix to the chassis number, with fuel-injected cars for the rest of the world prefixed CP. After the 1973 model changes the prefixes were changed to CR for injection cars and CF for the North American carburettor cars.

Lucas Mk2 Petrol Injection
Although new-fangled by the standards of the day when first launched, the Lucas system is in fact simple in its concept and is mechanical rather than electronic. Fuel is supplied at 110psi to the metering head driven off the distributor shaft, which contains a shuttle valve to distribute the fuel to the individual injectors. The total volume of fuel being introduced to the metering unit is determined by the control unit attached to the metering unit, which uses engine vacuum to move a control stop. A shaped cam determines the exact volume of fuel as engine load and vacuum changes, being in effect a hardware version of the software control ‘map’ stored in a modern injection system.
That’s simplifying it of course, but it’s an effective system when properly set-up with correctly functioning injectors and its high operating pressure does mean that the fuel is well atomised, which is why a properly set-up system can provide good power and economy.

Despite the relative simplicity of the concept though, it does require expertise to set up properly, in particular the inner workings of the metering and control units.

Triumph TR6 Buyers Guide

Unsurprisingly, it’s rust that will be your enemy with a TR6. Parts supply is superb, but obviously cost will mount up, as will the labour to stitch them into place. Major corrosion should be obvious and the door shuts are a good indication of either badly performed restoration work or serious corrosion. Despite the separate chassis, the sills are critical for bodyshell strength so need to be solid. Check where the sills meet the floor, as well as the floor panels. Costs can amount to over £1000 quite quickly with regards to the sills. Front inner wings can also be rotten, as can the scuttle panel.

There are many repair sections available, but costs can soon spiral as you uncover yet more rot beneath the surface, so be careful.

Underneath, major chassis rot should be obvious, but check for accident damage which may have kinked or distorted the rails. The outriggers support the body so need to be solid.

At the rear, corrosion around the rear suspension mountings is critical to safety and is difficult to repair, so if it looks bodged then walk away. The T-shaped reinforcement pressing around the cruciform section of the chassis is also crucial.

The scuttle and rear deck can be problem areas – and check the front inner wings, too. Hardtops are useful, but only if not rotten. If already fitted to the car, ask for it to be removed so you can check the condition of the hood. Check the mechanism as well because it can suffer from lack of use.

Triumph TR6 Buyers Guide

Armchair experts will tell you that the Lucas injection is the TR6’s Achilles’ Heel but these days the parts and knowledge are available to make the system reliable. More important is any end float in the crankshaft which in severe cases can cause the thrust washers drop out entirely. The accepted method of checking is to check the front engine pulley while the clutch is operated. Any noticeable play is bad news.

Meanwhile, one of the more common problems with the injection is the original pump overheating. It was a modified wiper motor so not up to the task and was also sited right above the rear exhaust section.

A common mod is a ‘fit and forget’ Bosch replacement pump for around £250. The Lucas system is in fact mechanical and not electronic, so if set up by an expert can be made reliable.

Before consulting the experts though, there are simple DIY checks you can make: the system relies on both engine vacuum and ignition timing to function properly, so check the timing is spot-on and that the vacuum hoses are intact and connected. It’s also useful to check that the valve clearances and camshaft timing are set correctly.

The TR4-derived gearbox is only just up to the power of the six-cylinder engine, so can get tired if it’s been driven hard. Problems should be obvious though, including whining and jumping out of gear. A box which is noisy in first/second/third but quiet in fourth is a sign of worn layshaft bearings. Overdrive should switch in and out easily, but low oil level can often be the cause if it won’t engage and wiring faults have been ruled out.

Second gear synchromesh is usually the first to fail, so try a few quick changes.

A clunking rear end can be the driveshaft joints, but the differential mounts can also pull away.

It’s a traditional setup with front discs and rear drums but works well to keep the 1122kg car under control. The usual problems are sticking front calipers and leaking rear wheel cylinders, both of which are easily fixed. If the car pulls to one side under braking then suspect a seized front caliper.

Triumph TR6 Buyers Guide

The TR6 is something of a mixture underneath, with its modern-sounding independent front wishbone suspension and telescopic dampers countered by the fact that it’s old enough to use trunnions. Meanwhile, the semi-trailing arm rear end uses lever arm dampers.

Those trunnions need regular lubrication and it’s a sign of an enthusiastic owner if this has been done.

It’s also a good idea to check where the lower wishbones meet the chassis as cracking can occur here. The steering should be free of play. Some TR6s now have power steering fitted. Either you’ll like it or you won’t.

The state of the dampers can make a huge difference to the driving experience. If the car feels skittish, it’s likely that new dampers would be a good idea. Some opt to replace the lever arm dampers with telescopic ones and it’s a common upgrade that firms up the back end.

Triumph TR6 Buyers Guide

Pretty much everything you might need is available from specialists, but retrimming a basket case restoration can still be expensive; especially if the veneered-wood dashboard needs replacing.

On the subject of trim, the hood is a pretty simple affair and a straightforward DIY prospect to replace.

Electrics are fairly reliable, though obviously the odd earth fault or dirty connection can cause items to fail. Make sure everything works.

Triumph TR6 Buyers Guide

Basket case imports from the USA can be an attractive way in, especially if they’re rust-free and complete. Beware though, as not all states are ‘dry’ states and US-market cars will be running the North American-spec twin-carb engine with a feeble 104bhp. Price have somewhat increased over the past year or so, with the ball park figure rising some 20% in value. MoT’d and usable UK-registered cars start at around £10,000, with plenty of nice, presentable cars around the £15,000 mark and the top-end cars fetching around the £25,000 mark with exceptional cars rising to £30,000-£35,000. Such is the parts availability and the DIY-friendly nature of these cars though that a cheaper, tatty but solid car can be a good-value way in if you know what you’re doing.

Tech Spec Triumph TR6 [CP]
ENGINE: 2498cc straight six
POWER: 150bhp at 5500rpm
TORQUE: 149 lb. at 3000 rpm
TOP SPEED: 117 mph
0-60mph: 8.5 sec
GEARS: four-speed overdrive
WEIGHT: 1122 kg

Our driver is a 45-year-old male, using his £15k TR6 as a second vehicle. It’s garaged, covers 3000 miles a year and lives in an SP2 postcode. He has no claims or convictions, is a club member, and is employed as a marketing manager.

Adrian Flux can provide comprehensive cover at £115, including a £100 excess for accidental damage, fire and theft. The policy includes free legal cover, agreed value option salvage retention, windscreen cover, courtesy car cover, aid cover and EU travel cover.