Saloon bar brawn: Rover P6 3500S vs Triumph 2.5 PI MkII

By Greg MacLeman

| 2 Dec 2021

Classic & Sports Car – Saloon bar brawn: Rover P6 3500S vs Triumph 2.5 PI MkII

Moments ago bright white flashes of brilliant lightning forked through the sky, and a torrential downpour hammered the Warwickshire hillside on which we’re perched.

Now, the calm following the summer deluge is about to be broken again, because cresting the hill through a dazzle of spray and sunshine come thundering two of the most desirable saloons of the 1970s – peak sporting iterations of the most advanced and successful four-door drivers’ cars from rivals Rover and Triumph.

“You hear both before you see them: first the six-cylinder song of the 2.5 PI, then the P6 3500S, adding a bassy note”

You hear both before you see them: first the six-cylinder song of the 2.5PI, the pinnacle of the Canley range; then the P6 3500S, adding a bassy note to the composition from its baritone Rover V8.

A world away from their cooking model cousins, they offer a combination of performance, handling and comfort unrivalled in period until the arrival of the Jaguar XJ6, and are as keenly matched for today’s sporting driver as for the bank managers, doctors and pilots in the sales brochures and adverts of the 1970s.

The shadow of the Avro Vulcan bomber seems a fitting place to settle a score.

The P6 heralded the beginning of a new era for Rover

Not because the aircraft did exactly that during Operation Black Buck in the midst of the Falklands conflict, but because it represents a huge technological leap from its forebears that meant its service continued long after its expected retirement.

Just like the cars sheltering under its wings.

Barely 11 years separate the jet-powered Vulcan from the piston-engined Lancaster, and a similar step-change in engineering advancement marked the arrival of the Rover P6 in ’63, which flipped the marque’s reputation for staid and dependable models like the P4 ’Auntie’ to something altogether more forward thinking.

The bold Rover grille out front (left), while the Continental Touring Kit saves boot space

That is not to say the firm had shied away from innovation: project leads on the P6 were none other than Spen King, Peter Wilks and Gordon Bashford, steered by the Wilks brothers, Maurice and Spencer; the names behind the revolutionary Land-Rover in 1948.

Some of the engineers’ early ambition inevitably had to be reined in, with everything from a gas-turbine engine to hydropneumatic suspension at one point being on the drawing board.

The front end was more reminiscent of the Citroën DS, with a streamlined nose and split bumpers, plus the trademark sloping roofline that did eventually make it to production.

By the time the design was signed off, the nose had been restyled into a more conventional squared-off grille with twin headlamps, although the body still tapered front and rear as if the car was slightly overinflated and spread outwards at the doors.

With 124bhp, the Triumph’s ‘six’ is outdone by the Rover’s venerable Buick-sourced V8

Just 10 miles down the road the finishing touches were being put to Triumph’s play at the executive market: the 2000.

Tracing its roots back to the Zebu project, a bold design encompassing everything from Lancia-style transaxles to a reverse-raked rear windscreen, the final product after being subsumed into the Leyland group was much more conventional.

It featured a monocoque shell and was powered by a derivation of the 2-litre straight-six found in the outgoing Vanguard.

Here’s the Rover’s ohv 3528cc V8, which delivers 150bhp plus 201lb ft of torque

All-round independent suspension was by MacPherson struts at the front and semi-trailing arms and coil springs at the rear, while its body was penned by Giovanni Michelotti, who had such success styling the Spitfire.

Its shark-faced nose and the Italian’s trademark strakes from the rear arches gave more of a sporting feel, which was echoed in the specification.

In a market previously dominated by the big three-litre Farinas, the Triumph’s lusty ’six’ offered performance, economy and – most crucially – refinement, especially when compared with the Rover’s busier ’four’.

Warm veneers attempt to add a hint of luxury to the cabins of both the Rover (left) and the Triumph

It’s hard to argue with either car given the improvement over what had come before, but the 90bhp brought to the table by Triumph’s 1998cc straight-six and the peppier but noisier 1978cc four-pot designed for the P6 soon felt underpowered.

Buyers had to wait another five years before things got really interesting.

Rover’s attempt to both increase performance and put clear air between the P6 and its Triumph rival was fairly simple, and much more affordable than the gas-turbine dream: in 1968 it took the 3528cc Buick V8 – already on stream in the P5 – and dropped it into the P6’s spacious engine bay.

The all-alloy construction meant little weight was added, while performance was drastically increased thanks to a marked boost in power to 146bhp.

“It’s hard to argue with either car given the improvement over what had come before”

The P6 went from being a comfortable executive express to borderline muscle car, with a 0-60mph sprint time of just 10.5 secs and a licence-troubling top speed of 114mph.

Pressed by the arrival of the more powerful Rover 2200TC, rumours of the impending 3500 and with its own in-house V8 too far off, the engineers at Canley looked to the top-performance iteration of its silky ’six’: the 150bhp Lucas fuel-injected version that had made its debut in the TR5 roadster in August 1967.

Stroked to 2498cc, it had the low-down grunt needed by the heavier saloon, and even with a slightly more mellow camshaft, different metering unit and single tailpipe limiting power to 132bhp, the PI engine delivered the sort of performance previously only seen on the triple-carbed rally cars of the works ranks.

If the Triumph’s interior or punchy engine don’t impress you, the soundtrack surely will

By then both models were getting a little long in the tooth. Rover freshened things up with smart interior instrumentation, new rear lights, bonnet bulges across all models – not just the V8 – and a redesigned air intake, but kept the same overall shape for the 1970 Series II.

Triumph’s facelift, on the other hand, was rather more comprehensive.

Michelotti was again entrusted with the task, restyling the front end and nose in the modern image of the Stag and reworking the back end with horizontal tail-lights and a bigger boot.

The cabin was also overhauled in another sneak preview of the imminent Stag, with a clear and clean new dashboard that canted the instruments towards the driver.

“The 3500S became an instant performance legend, slashing the 0-60mph time to around nine seconds and even improving fuel consumption”

Triumph tended to attract the more enthusiastic owner throughout the 1960s, but that all changed in 1971 when, for the first time, punters could specify a four-speed manual gearbox instead of the ubiquitous Borg-Warner 35 three-speed automatic in the P6.

The 3500S became an instant performance legend, slashing the 0-60mph time to around nine seconds and even improving fuel consumption – not bad for what was essentially a beefed-up version of the ’box from the four-cylinder cars.

Questions remained over whether the fragile gearbox was up to the task, which is no doubt a contributing factor to the rarity of the model on today’s roads.

But stepping up to Peter Reeve’s stunning Almond example, it’s clear that the 3500S is the pinnacle of the breed.

The Triumph’s wing mirrors are a case of style over practicality

Something of a sleeper, you have to get quite close to spot the telltale ’V8’ badging, and you’ll only realise it’s an ’S’ once you pop the heavy door and slide into the luxurious cabin.

Both cars were aimed squarely at a generation of successful and aspirational post-war professionals for whom the interior appointments were as important as the powerplant, and that meant a level of comfort and luxury above what you would find in a Ford or Vauxhall.

Reeve’s restored 1974 example is as tidy and correct as if it just rolled out of the showroom, with its optional cloth seats, sculpted front and rear, and beautifully refurbished switchgear and brightwork.

The impressive cabin is cosy considering the car’s size and finished impeccably. Every touchpoint feels solid and well engineered, from the polished wood-rimmed steering wheel to the dark wood trim and thick carpets, with neat details such as the translucent green heater and fan controls adding individuality.

This stunning Almond Rover P6 is almost half a second quicker to 50mph than its Triumph rival

Luigi Maio’s Pimento Red 1972 Triumph 2.5 PI is similarly a fine example of its type, with a standard interior featuring comfortable corded Bri-Nylon chairs, a rear bench and lashings of veneer to the dash and door cappings.

It feels that bit more modern than the Rover, helped by the clear dashboard layout and well thought out parcel shelf below the glovebox.

A slightly longer wheelbase and wider track than the P6 makes it bigger inside, adding 2½in of rear legroom, but it feels more spacious still thanks to its clever layout and neat furniture, plus superb visibility from the boxy glasshouse.

Intelligent as the design is, it does lose out slightly to the quality of fixtures in its rival – the small details such as the indicator stalks and quarterlight mechanisms, for example, just feel better engineered and more expensive in the Rover.

Triumph and Rover had the executive saloon market sewn up in the 1960s

Any thoughts of fixtures and fittings evaporate as soon as you spark the meaty straight-six into life – the beating heart that separates the 2.5 PI from lesser Triumph saloons.

Power dropped from 132bhp to 124bhp in 1972 thanks to rationalisation of components with the TR6 range, but the PI is still a lively performer with superb throttle response that lifts the nose on its compliant springs.

The rugged J-type overdrive four-speed is a joy to use, with a long throw that quickly becomes second nature, and one of the best classic soundtracks is only enhanced by the addition of a Chris Witor sports exhaust, which produces a note that gets ever more scintillating the higher up the rev range you climb.

The Rover immediately feels more stately, with its bigger V8 providing a more muted score on start-up.

These are both fantastic examples of their type

It’s only when you bear down on the throttle and hold the gears that the familiar music begins to play.

The four-speed manual gearbox may have a poor reputation for reliability, but in Reeve’s car it’s a honey with a smooth action and neat, narrow gate that just edges the Triumph – aided by the addition of an aftermarket servo to lighten the clutch.

Despite carrying 40kg more timber than the PI, the sweet Rover V8 powerplant more than compensates.

The P6 is noticeably quicker to 50mph to the tune of almost half a second and storms beyond the Triumph’s top speed despite a shorter final-drive ratio. It’s also more usable around town thanks to all that low-down torque.

The 2.5 PI shows its familial lineage as it chases the V8 Rover, with similar rear lights across the whole Triumph range

Triumph and Rover’s greatest rivalry was the P6 and 2000, their biggest battleground always for the hearts and minds of middle management boomers.

In the beginning you couldn’t slip a cigarette paper between the two saloons, and the same holds true as much today as when the 2.5PI and 3500S bowed out in the late 1970s.

Almost an even match for performance and luxury, but each with its flaws; the Rover for its chocolate manual gearbox, and the Triumph its troublesome mechanical fuel injection.

Still, it’s hard to say no to either. It doesn’t matter if you drink single malt or a blend, you’ll still have a great time – even if you do occasionally wake up with a headache.

Images: Luc Lacey

Thanks to The Triumph 2000 2500-2.5 Register; The Rover P6 Club; XM655 Maintenance & Preservation Society

Factfiles

Rover P6 3500S

Sold/number built 1971-'76/2715
Construction steel monocoque with bolt-on body panels, alloy boot and bonnet
Engine all-aluminium overhead-valve 3528cc V8 with twin SU carburettors
Max power 150bhp @ 5000rpm
Max torque 201lb ft @ 2750rpm
Transmission four-speed manual, RWD
Suspension at front independent, by transverse lowerlinks, leading upper links acting on horizontal coil springs, anti-roll bar rear coil springs, fixed-length driveshafts, stabiliser rod, de Dion sliding tube, fore/aft Watt linkages; telescopic dampers f/r
Steering recirculating ball
Brakes discs, inboard at rear, with servo
Length 15ft (4566mm)
Width 5ft 6in (1676mm)
Height 4ft 8in (1422mm)
Wheelbase 8ft 7in (2625mm)
Weight 2855lb (1295kg)
0-60mph 9.1 secs
Top speed 125mph
Mpg 20.8
Price new £1976 13s
Price now £5-20,000*

Triumph 2.5 PI MkII

Sold/number built 1969-'75/49,742
Construction steel monocoque
Engine all-iron overhead-valve 2498cc straight-six with Lucas mechanical fuel injection
Max power 124bhp @ 5500rpm
Max torque 153lb ft @ 2000rpm
Transmission four-speed manual with overdrive or three-speed auto, RWD
Suspension independent, at front by MacPherson struts rear semitrailing arms with coil springs; antiroll bar f/r
Steering rack and pinion
Brakes discs front/drums rear, with servo
Length 15ft 2in (4631mm)
Width 5ft 5in (1651mm)
Height 4ft 8in (1422mm)
Wheelbase 8ft 10in (2692mm)
Weight 2767lb (1255kg)
0-60mph 11.5 secs
Top speed 107mph
Mpg 21.8
Price new £1595 1s 4d
Price now £5-15,000*