In 1975, some five years after the agreement was signed that led to the birth of the Franco-Swedish engine company, comprising Peugeot, Renault and Volvo, the V6 engine appeared. The design of the engine was originally set in motion more than seven years previously, and the first customer for the 2.6-liter V6 was, naturally enough, Peugeot, who chose it for the 604.
The Pininfarina-designed 604 was unveiled at the Geneva Motor Show in March 1975, with sales beginning in September of that year. It was based on the chassis of the Peugeot 504, using its doors, and represented Peugeot's first entry into the large luxury sedan market for 40 years (the last being the short-lived Peugeot 601 of 1934).
By European standards the 604 was quite a large car, with an overall length of 15.48 ft (4.71 m). Its design features remained in the classic style of the then current Peugeots, the line only broken by the massive bumpers. The 604 had an air of quiet assuurance, uniting a certain distinction usually found in cars of this class, with the tradiitional Peugeot dignity.
Technically, the 604 was a development of the 504
, and the rear-wheel drive saloon inherited the same well thought-out suspension. However, an improvement had been made in the damping out of vibration and excessive movement of the rear axle.
The interior of the 604 offered plenty of space, with 4.85 ft width fore (1.48 m) and aft providing a useful space from toeboard to the back of the rear seat of 6.26 ft (1.91 m). The seats, of nylon velour, were luxurious and well-designed, but the mediocre dashboard was unworthy of a car of its class. Although reasonably complete, there were two important gaps: no maximum limit markings on the rev-counter, and no warning light on the petrol gauge.
The four courtesy lights were a sound feature of the general equipment, as was the efficient heater, which could deliver warm air to the back seats. Other features included inertia-reel seatbelts, fitted with energy absorbers (a Peugeot-Renault specialty), and a laminated windscreen. On the other hand, it seemed a pity that on a prestige car the steering wheel was so large and not adjustable for height, nor was the driver's seat, although the runners were curved.
It would also have been in keeping with the 604's class if an intermittent switch had been fitted to the wipers, and a central locking device made standard.
The Oversquare Engine, And Crude Solution To Vibration
The engine took a long time to develop, due mainly to the aluminum construction. The V6 engine itself was "oversquare
", a 90 degree
design chosen with the view of later developing a V8 from it - a project which was subsequently abandoned. The oversquare engine design was bound to introduce unwanted vibration, so Peugeot (and Renault) suppressed the vibrations via the crude solution of introducing a two degree difference in timing between each bank of cylinders.
The engine breathed through carburetters, and not only was its power-output disappointing, but also, which was more serious, torque was best described as modest. In comparison with other six-cylinder engines, the 604 developed 51 hp/liter (38 kW/liter) and 152.53lb ft maximum torque (21.1 mkg) at 3500rpm, which put it last in the category - and by todays standards it would at best be described as lethargic.
Fortunately, the engine torque curve was good, and when accelerating from 1500 rpm, there was an agreeable liveliness. However, pick-up was much too slow, and the petrol consumption too high, being around 14 mpg (20 lit/100 km).
In all other departments, the Peugeot merits nothing but praise. The manual gearbox was good, and so was the automatic transmission, the steering was precise, and sufficiently sensitive, thanks to variable-rate power assistance. Roadholding was good, the normal understeer becoming neutral at the limit. Lighting was powerful, road and engine noise very low, braking well-balanced, and above all the ride and passenger comfort were exemplary.
The Peugeot 604 is not particularly collectable, however for the time it was refined and well polished in most areas. Disappointing then that the main feature of the car, the V6 engine, was such a let down. Build quality problems added to the cars woes. Sales, which were never particularly strong, dipped in 1980 following the launch of the 505, and the last 604 rolled off the production line in 1985. Peugeot's next major executive car, the 605, was launched in 1989.