The AC Frua or AC 428 is a British sports GT built by AC Cars from 1965 to 1973.

History

The first version was presented at the London Motor Show in 1965 a prototype, two-seater convertible which was followed by the presentation of the 428 coupes with a fastback body at the Geneva show in 1966.Main production began between the end of 1966 and the beginning of 1967, continuing until 1973.With an Italian body, British chassis, and American big block V8 it is a true hybrid. Production was 81 cars built in total: 49 coupés (known as fastbacks), 29 roadsters convertibles, and 3 prototypes special bodied.  The company, which was managed by Charles and Derek Hurlock at the time, wanted to continue the tradition of the previous Cobra. The idea was to provide the well-known and proven chassis of the AC Cobra.

The Frua is built on an AC Cobra 427 Mark III chassis tube frame extended by 6 inches (150 mm) Chassis were built at the AC plant in England then shipped to Frua's workshop in Italy where the body was fitted and then sent back to England to have the power train and trim added Chassis construction was similar to most Italian supercars of that era, with square and rectangular tubing connecting the steel body to the frame The AC Frua may be confused with the very similar looking Pietro Frua designed Maserati Mistral. However, only the front quarter windows and door handles are shared. 

The chassis with new steel coupé or spider body designed by Frua in Turin. Produced exclusively by AC between 1966 and 1973 with no influence from Shelby.Cobra Mark III production began on 1 January 1965; two prototypes had been sent to the United States in October 1964. Cars were sent to the US as unpainted rolling chassis, and they were finished in Shelby's workshop. Although an impressive automobile, the car was a financial failure and did not sell well. In fact to save cost, most AC Cobra 427s were actually fitted with Ford's 428 cubic inches (7.01 L) engine, a long stroke, smaller bore, lower cost engine, intended for road use rather than racing.

A new chassis was required developed and designated Mark III. CSX2196 was revised for the show down at Nassau which allowed a more relaxed class division of racing. This allowed the GT cobras to run with prototype Ford GT, GM Grand Sport Corvett

The new car was designed in cooperation with Ford in Detroit. A new chassis was built using 4 in (102 mm) main chassis tubes (up from 3 in (76 mm)) and coil spring suspension all around. The new car also had wide fenders and a larger radiator opening. It was powered by the "side oiler" Ford 427 engine (7.0 L) rated at 425 bhp (317 kW), which provided a top speed of 164 mph (262 km/h) in the standard model and 485 bhp (362 kW) with a top speed of 185 mph (298 km/h) in the competition model.

Engine: V.8 built by the Ford Motor Co. of America, 7,016 c.c. along with a high performance engine also available, providing 400 b.h.p. at 5,750 r.p.m.at extra cost. optional automatic gearbox also ratios, available at extra chargepower to rear via propeller shaft with Hardy Spicer needle type universal joints transmits drive to rear wheels by short halfshafts using similar joints with Salisbury limited slip differential with a 2.88 ratio is located on 3-point rubber
mountings.

Luxury touring body styled by Frua. The main chassis frame comprises 4 in. steel tubing running from front to rear cross-braced as necessary with sub-frames to support panel work fixed direct to tubes; rack and pinion steering; polished wood and aluminium steering wheel; disc brakes to all wheels, swept area 580 sq. in., front 113/4 in. diameter, rear 10 1/2 in. diameter, double master cylinder system with twin servo actuation; 15 in. road wheels with 6 in. rims, triple laced.Leather trim, with carpets, all to colour choice
from available samples; soft top retracts fully below deck cover; deep windshield with curved frameless electrically operated door windows; large 10 sq. ft. capacity luggage boot and 18 gal. tank.

The front suspension comprises twin wishbones fabricated from circular section tube and have rubber bushed chassis pivots and sealed ball joints for attachment to the vertical links, co-axial coil springs and telescopic dampers operate on the lower wishbones front and rear, the whole suspension system is mounted on rubber bushes, sealed rose ball joints and precision made hemispheres, very little service attention is required, anti-dive and anti-squat geometry contribute to the excellent road holding.The rear suspension is of twin tubular wishbone type, radius rods, for longitudinal location are used in conjunction with the lower wishbones which are of the inverted type and afford directional control of the rear wheels; cast brackets between the upper and lower wishbones carry the housings for the hub bearings, the coil spring and damper units which are behind the suspension links operate on the lower wishbones; the suspension system allows provision for independent adjustment of camber and wheel alignment.

Though the 4-inch (100 mm) tubular chassis allowed both coupé and convertible versions to be rigid, the design was intricate and prone to rust. The bonnets and boot lids were fabricated from aluminium. The cost was high and the cars could not be sold at a competitive price. Unlike similar cars such as the Iso Grifo, Iso Rivolta, Monteverdi, and De Tomaso models of the period, the AC Frua features Front engine, rear drive fully independent racing-based coil spring suspension. Fully adjustable independent suspension with double triangular wishbones, coil spring hydraulic telescopic shock absorbers at the front, at the rear adjustable independent suspension with double triangular wishbones, coil spring hydraulic telescopic shock absorbers.

First, the 6997 cc eight-cylinder Ford engine was installed, which was from the AC Cobra 427, with 385 hp (287 kW) at 5600 rpm. In March 1968 the engine was switched to Ford's larger "428" engine with 7016 cc displacement, which made 345 hp (257 kW) at 4600 rpm.

The AC Frua was never fully developed because AC Cars lacked the financial means. The car's main drawback is a tendency of the V8s heat to bleed into the cabin. with a Fully synchronized 4-speed Ford Toploader transmission (close-ratio) or 3 speed automatic Ford C6 transmission with rear differential Salisbury, limited slip with Ratios: Automatic 2.88, Manual 3.08.Brakes Four discs power assisted "Girling" 3 pistons, dual remote servo assistance. The distribution of weight was 47.4% front axle, and 52.6% at rear axle

PERFORMANCE

• engine capacity: 428.12 cu in, 7,016 cu cm
• fuel consumption: 17 m/imp gal, 14.2 m/US gal, 16.6 1 x 100 km
• max speed: 150 mph, 241.5 km/h
• power-weight ratio: 8.8 lb/hp, 4 kg/hp
• max power (SAE): 345 hp at 4,600 rpm
• max torque (SAE): 462 1b ft, 63.8 kg m at 2,800 rpm
• max engine rpm: 5,250
• specific power: 49.2 hp/l
• max speeds: 67 mph, 107.9 km/h in 1st gear; 93 mph, 149.7 km/h in 2nd gear; 121 mph, 194.8 km/h in 3rd gear; 150 mph, 241.5 km/h in 4th gear

The AC Frua competed with Ferrari, Lamborghini, and Maserati models. Built over a stretched AC Cobra 427 chassis, the car had immense performance; the big-block Ford FE engine had larger capacity, more torque and more power than similar Italian cars, but in a car of similar weight.

This one AC that joined that select company of very fast, very luxurious touring automobiles from the 1960s. The AC 428 coupé sported a recommended UK retail price of £5,573 (including automatic transmission), to the manual transmission Aston Martin DB6's £4,460 - itself roughly twice that of a 4.2 litre Jaguar E-Type roadster at £2,225.

Towards the end of the production run a couple of prototypes for an extended range were produced. There was a four-door version of the coupe and a more streamlined version of the convertible that included electrically operated "pop-up" headlamps. Neither were developed due to the precarious state of the company finances. Production of the AC 428 ended in the summer of 1973. There were many reasons for this. The AC was very expensive but on the other hand, the market for large and fast sports cars increasingly collapsed in view of the looming oil crisis.

Number of cars built 49 coupes, 29 convertibles and 3 special bodied cars.