Ferrari's reaction to the LP500 S came rather quick, with their TestaRossa from 1984, they had a car that pumped out 390 Bhp, but the Countach was again updated.
On the 1985 Geneva Auto Show, Lamborghini unveiled their answer, the Super-Countach, the QuattroValvole, with its 455 Bhp, it made the TestaRossa eat dust.
Even Ferrari's limited production 288 GTO only managed 400 Bhp, so the Countach was again at the top of the super car world.
The displacement of this new engine became 5167 cc by enlarging the stroke to 75 mm, the compression ratio was 9.5:1 and, for the first time on the Countach, downdraft Weber carburetors were used. Because of these carburetors, the engine lid received a large hump in the middle, making the rear visibility even worse. Another change were the front tires, they became a little larger and therefore the suspension was altered to suit.
The rear tires were still the massive 345/35-15 Pirelli P7's, which were actually created especially for the Countach, just like the four-piston brake calipers which ATE made exclusively for this Lamborghini. On the inside nothing much changed, only by now air-conditioning was usually installed.
By 1986, the Countach was again exported to the United States, special 'crash' bumpers were installed to front and rear, and a new Bosch KE-Jetronic fuel injection was used instead of the Weber carburetors, to meet demands by the DOT and EPA regulations. SAE horsepower was still 420 Bhp, only eight percent below the European specifications cars, a difference nobody really noticed, and it was still more than any Ferrari.
The Countach Quattrovalvole received small bodywork changes in late 1987, new streaked sills incorporating rear brake cooling vents were added. The interior was now equipped with central-locking, modified heater controls and much improved ventilation. The huge rear wing could still be ordered on the Quattrovalvole, and few Countach left the factory without one, but it is however completely useless. The Countach does not suffer from aerodynamic lift at high speeds, so the rear wing only adds drag, a lot of cost (it was still an expensive option at about US $ 5000) and most important, a lower top speed.
The Countach Quattrovalvole built before 1987, so those without the sills and cars without the massive rear wing, are believed to be the best looking Countach ever. It is also the most powerful one, and it is said that this is how the Countach should have been from the beginning. The latest Countach, the 25th Anniversary, used the same engine, but the bodywork was much less aggressive-looking, so if you want to buy a Countach, buy a QV.
The LamboCARS.com extensive specifications chart on Countach LP500 Quattrovalvole ...