The AC Frua or AC 428 is a British GT car of the 1960s and early 1970s. Built by AC Cars from 1965 to 1973, it is extremely rare with only 81 cars built in total, 49 coupés (known as fastbacks), 29 convertibles and 3 special bodied. The car is built on the AC Cobra 427 Mark III race-bred coil springs chassis but 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. The cost was huge and the cars could not be sold at a competitive price. Unlike similar cars such as the Iso Grifo, Iso Rivolta, and Monteverdis and De Tomasos of the period, the AC Frua features fully independent racing based coil spring suspension. It is often confused with the very similar looking Maserati Mistral also designed by Pietro Frua. (There is a common belief that the two cars share most of their body panels, but in reality only the front quarter windows and the door handles are the same.)
Construction was similar to most Italian supercars of that era with square and rectangular tubing connecting the steel body to the frame. There were aluminium bonnets & boot lids. The design was intricate and prone to rust. Because of its huge 4 inch (100 mm) tubular chassis, the car was immensely rigid in both coupé and convertible versions. Chassis numbering went as follows: CF## for cars sold in Britain and CFX## for export models.
The AC Frua was never fully developed because AC Cars lacked the financial means. The car's main drawback, which is also common to the similarly-engined big-block United States muscle cars of the period, is a tendency to dissipate the heat produced by the huge engine into the cabin. But this design flaw can be overcome by using modern insulation on the firewall and under the floor.
John Mclellan said in his book "Classic ACs, Auto Carrier to Cobra" that Dereck Hurlock once said to journalist Mike Tailor: " I like the 428 because it fits my image of a true GT Car". He also quoted the magazine Autocar which said the following about the AC 428: "Like anything exclusive, especially from craftmen, it costs a lot of money. For this you get one of the fastest cars on the road, guaranteed to make an impression anywhere, and backed by a small company who cares. This one AC that joined that select company of very fast, very luxurious touring automobiles which moved effortlessly from current model to collector's piece".
Due to the rarity of the car, body parts can be very difficult or impossible to obtain. However, all mechanical parts are available through Ford or various Cobra suppliers. The car is extremely reliable and maintenance is easy and relatively inexpensive compared to other exotics of the period because of the Ford powertrain and AC Cobra suspension and chassis.
With a little tweaking the car can be made as quick as, or even quicker, than a Cobra because of its improved aerodynamics, and the chassis is more than able to handle vast amounts of power. Five hundred horsepower (370 kW) is relatively easy to achieve with the 428 motor and the 427 "side oiler" motor can easily achieve in excess of 600 hp (450 kW) on "pump gas" (91 octane). With this type of power the car is one of the fastest road going automobile of that era.
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.
A few of the coupes have been destroyed in the past and converted into Cobra replicas— but as pricing has been rising steadily in recent years, this practice has stopped. It is now much cheaper to buy a Kirkham rolling chassis to build an exact Cobra replica than to butcher an AC Frua.
|AC Frua Technical Data|
|Chassis||"AC Cobra 427 Mark III" four inch (100 mm) tube frame extended by 6 inches (150 mm). Front engine, rear drive.|
|Engine||Iron "big block" Ford FE 428, some models fitted with higher performance crossover bolted Ford 427 engine (side oiler). Hydraulic lifter, Autolite or Holley four barrels carburator. (Specifications can vary substantially between each car).|
|Bore & stroke||104.9 X 101.2 mm, 10, 5:1 compression.|
|Capacity||428: , 427: .|
|Power||428: @ 4,600 rpm, 427: @ 5600 rpm|
|Torque||428: @ 2,800 rpm, 427: @ 3200 rpm|
|Transmission||Fully-synchronized 4 speed Ford "Toploader Transmission" close-ratio or 3 speed automatic Ford C6 transmission.|
|Steering||Rack & Pinion.|
|Front suspension||Fully adjustable independent suspension with double triangular wishbones, coil spring hydraulic telescopic shock absorbers.|
|Rear suspension||Adjustable independent suspension with double triangular wishbones, coil spring hydraulic telescopic shock absorbers.|
|Differential||Salisbury, limited slip. Ratio: Automatic 2.88, Manual 3.08.|
|Brakes||Four discs power assisted "Girling" 3 pistons, dual remote servo assistance.|
|Body||Coach-built steel body over extruded rectangular and square tubing.|
|Measurements||X X ; Wheelbase .|
|Maximum speed||Manual Transmission: More than , 0 to 100 km/h (0-62 mph): 5.4 s (Autosport Magazine); Automatic Transmission: , 0 to 100 km/h (0-62 mph) 5.7 s.|
|Production life||1965 to 1973|
|Number of cars built||49 coupes, 29 convertibles and 3 special bodied cars.|