The British motor industry of the 1960s gave us legends – the Jaguar E-Type, Aston Martin DB5, Lotus Elan and MGB. But by the early 1970s, the British manufacturers were struggling to keep pace with the world. Constant labour disputes and a general stagnation of innovation was starting to eat away at the reputation of British cars. And nowhere is there a better example of this decay and folly better then the notorious Triumph V8.

By 1964, Triumph had built a long reputation building pokey four-cylinder sports cars that leaked water on the passengers and oil on driveways, but the cars were just so darn fun to drive that most didn’t care. That year, Triumph decided in earnest to develop a 1963 styling exercise by the famed Giovanni Michelotti and turn it into a real production car. This four-seat, open-top GT car would go on to become the Triumph Stag, introduced in 1970.

The styling was indeed spot-on and it featured a unique T-bar roof that allowed it to be driven with a cloth top, removable hard-top, or no top at all for open-air motoring. Triumph was aiming for mid-range GT cars like the Porsche 911, and to do so they needed more power than the traditional inline-four could provide.

Initially a 2.5-litre version of Triumph’s own inline-six was considered, but engineers believed it would not provide the power or refinement that GT buyers expected in the segment. There was also the discussion of whether the model should use the familiar Rover 3.5L V8. But in the end it was decided to use a Triumph-designed engine because engineers were already nearly done with a brand-new engine, and because they wanted to show the world what Triumph engineering could do. Unfortunately, they did.

Triumph’s solution was to twin their existing inline-four into a 2.5L V8. The I4 had actually been designed with this in mind and the reverse had been done before by Pontiac, turning half a V8 into a slant-four. Thus began an extremely lengthy (and costly) five-year development program between 1964 and 1969. Originally, the 2.5L engine was planned to use Bosch mechanical fuel injection, but reliability became an issue and Triumph felt that they wouldn’t be able to make the injected engine meet U.S. emission requirements. So, the complex injection system was ditched and replaced with a simple, but less efficient twin-carbureted setup.

Though the engine now ran smoothly and cleanly enough to be sold in the US, the carbs made less power than the injected version and Triumph felt the engine would now have to be 3 litres instead of 2.5 to make the same power. Rather than increase displacement by stroking the engine via a crankshaft with a longer throw, Triumph decided to widen the cylinder bores. The wider bores did indeed gain that half-litre of displacement, but it also gave the engine two unhappy side-effects: Firstly, the engine was now massively oversquare and torque suffered as a result. But more critically, the larger bores ate up into the space where the coolant passages were located and they had to be downsized to fit the larger cylinders. The engine was now larger and had less internal cooling capacity.

And the cooling woes were exacerbated by the awful execution of the water pump assembly. Nearly every car has a water pump that’s driven from the accessory belt at the front of the motor. Triumph in their infinite wisdom mounted the water pump on top of the engine, in the valley of the “V” and drive that water pump internally through a geared jack-shaft. The gears were known to shear without warning, causing the water pump to stop spinning. Making matters worse was the fact that when parked on level ground, the water pump was higher than the radiator fill cap. This meant that unless you tilted the car on an angle via a jack, you could never fill the coolant system with enough fluid to actually reach the water pump.

It also meant that when coolant burnt or leaked out that the first part to go dry was the water pump. So, a leak would stop coolant from circulating, overheat the engine, and usually destroy the water pump gears and bearings in the process. Brilliant.

The Triumph V8 uses an aluminum head and and iron block. This is not uncommon and not a giant issue in and of itself, but it does mean that you must run special corrosion-inhibiting coolant to prevent internal electrolytic corrosion of the system. This was not widely known, even at a dealership level, and very few used the correct coolant in period. Making cooling matters even worse was to save money, Triumph located the coolant temperature sender in one of the cylinder heads. This is fine for the inline-four engine whose head was designed for. But in a V8 with two cylinder heads, it means that the other head could go full nuclear meltdown and the gauge would read normal. Most V8s place the sender on the water pump for this very reason.

But perhaps the most bungled design decision of them all – and there were many – was the bizarre idea to use head studs at two different angles on the same head. The head stud is a sturdy bolt that clamps the head to the block and in most engines, those studs runs exactly perpendicular to the deck of the block. Triumph mounted half the head studs this way, but mounted the other half about 20-degrees akimbo to the deck of the block.

The idea was that skewing the studs this way would allow technicians to replace the head gaskets without removing the camshafts and setting all the valves; a lengthy process. What it inadvertently did was cause major warping issues for the cylinder heads. The straight studs heated up differently than the longer splayed studs and because of this, when the engine got hot, the cylinder head was subjected to strange side loads that promoted warpage. To make matters worse, the long steel studs had a habit of fusing solid to the aluminum head and then because they were at dissimilar angles, one couldn’t simply saw the head off the offending bolt and yank the head.

Other issues included main bearings that were simply too small and failed regularly, and extremely long single row timing chain that stretched and needed to be replaced every 40,000 kilometers. It was also an interference engine, so when the timing chain went, it destroyed the valves and pistons too.

Triumph intended to run the V8 in other models, but the disastrous performance and abundance of the similarly sized Rover 3.5L V8 sealed its fate. The Stag was sold until 1977 and it was the Triumph V8’s only home. Just 25,877 examples were made, and of those, just under 3,000 were sold in the U.S. The engine definitely hurt sales and one can’t help but wonder what could have been if Triumph had only used the Rover 3.5.

Despite all this, the engine is not without its upsides. The small-displacement mill sounds downright angry at full-throttle and some were successfully campaigned as race cars. In fact, 91 per cent of Stags still on the road today still have the Triumph V8 powering them. Honestly, it’s likely more of a testament to the resilience of the owners rather than the reliability of the engine, but its something to be commended all the same. As a car, the Stag was a handsome grand-tourer and a brave move in a changing automotive clime. It’s just a shame that it had the worst engine ever.