Installing a V-8 engine is often viewed as the ultimate upgrade for any vehicle. However, history shows that this modification can sometimes backfire, upsetting the car’s delicate balance, altering its character, or introducing reliability issues that permanently damage its reputation. Here are five instances where adding extra cylinders resulted in a worse overall package.

1. 1970–1977 Triumph Stag

Designed as a luxury roadster to boost Triumph’s market share, the Stag was intended to be a comfortable cruiser. Originally, the car was designed to utilize the company’s proven 2.0-liter or 2.5-liter inline-six engines. However, in a bid for prestige, executives opted for a custom 2.5-liter V-8.

The result was catastrophic. As one observer noted, the engine was essentially two four-cylinder units joined together, leading to severe design flaws:

«The engine was a total disaster. It suffered from narrow coolant passages, weak head studs, and a flawed timing chain design, turning a promising roadster into an overheating, unreliable mess.»

The car’s poor reputation for reliability killed its potential, especially after the brand abandoned the dependable I-6 platform.

2. 1996–1999 Ford Taurus SHO

The original Taurus SHO was celebrated for its high-revving Yamaha-tuned V-6 and engaging manual transmission. When Ford redesigned the Taurus in 1996, it introduced a new 3.4-liter V-8. Despite the extra cylinders, the new engine offered only a marginal power increase, and the beloved manual transmission was dropped in favor of a sluggish automatic.

Mechanical failures, particularly involving the camshaft sprockets, further plagued the model. Ultimately, the V-8 transition contributed to the vehicle's poor sales and temporary discontinuation.

3. The GM Front-Wheel-Drive V-8 Era (2005–2009)

General Motors attempted to inject excitement into its midsize sedan lineup—including the Chevrolet Monte Carlo SS, Impala SS, Pontiac Grand Prix GXP, and Buick LaCrosse Super—by dropping in a 5.3-liter LS4 V-8. These cars were never designed to handle the massive torque steer generated by such powerful engines on a front-wheel-drive platform.

The V-8s struggled with fuel economy and compromised the handling balance that the previous supercharged V-6 models had mastered. The market rejected these experiments, and they were phased out by 2009.

4. 2008–2013 BMW M3

The transition from the legendary S54 inline-six to a 4.0-liter V-8 in the E90/E92 generation remains a divisive topic. While the V-8 provided impressive peak horsepower, it added significant weight to the front of the car.

The engine required high RPMs to access its power, making it feel less practical for daily commuting compared to its predecessor. Recognizing this, BMW returned to turbocharged six-cylinder engines for subsequent generations, acknowledging that the V-8 was not the ideal fit for the M3's formula.

5. 2022–2025 Lexus IS 500

Lexus attempted to revive the spirit of its high-performance IS F by placing a 5.0-liter V-8 into the standard IS sedan. However, the manufacturer failed to upgrade the chassis, suspension, or brakes to match the engine's 472-horsepower output.

The result was a car that struggled to manage its own power. Despite a great exhaust note, the platform felt outdated and overwhelmed, leading to the model being quietly withdrawn from the market as Lexus pivoted away from the eight-cylinder option.