The Formula 850 was a continuation of the Formula 500 series in 1966. The Formula 850 (otto e mezzo) was raced with monopostos that had to meet the following requirements:
The cars were of the single-seat racing type with engines derived from an Italian make car approved in the Touring series category (Group 1)
- Maximum cylinder capacity: 850 cc
- Minimum track width: 105 cm
- Minimum wheelbase: 180 cm
- Minimum weight roadworthy and without fuel: 300 kg
- Maximum external width of the body: 90 cm
- The use of movable ballast was prohibited.
The engine had to be strictly standard like that of the homologated car from which it was derived and only the following modifications, replacements or deletions were allowed to the engine:
- Exhaust manifold and silencer:
A proprietary exhaust system was allowed to replace the manifold and muffler.
The air filter could be removed or replaced.
The carburettor that was normally mounted on the engine could not be replaced or converted.
However, it was allowed to change the parts that control the dosage of the fuel and air.
It was allowed to replace, move and / or modify the radiator, the water pump, the associated pipes and supports with parts from other brands.
Change or removal of the fan and thermostat was allowed.
In the case of an air-cooled engine, it was allowed to modify or relocate the ventilation system, but not to remove it.
- Electrical system:
It was allowed to remove the alternator and the voltage regulator.
It was allowed to replace, remove or add sensors on the engine for odometers, tachometers, thermometers and water and oil pressure gauges.
- The gearbox had to be of the same make as the engine, even if it belonged to a different car model.
- Gear ratios had to remain standard.
The gear ratio replacement was only allowed if it had been approved by the manufacturer, also for another type of car belonging to group 1.
- When mounting a gearbox other than the original, this modification allowed the fitting of an intermediate flange on the engine and gearbox.
This flange could support the starter motor support and the intermediate shaft between the clutch and gearbox.
The open single-seat body had to be fitted with a roll bar at the driver's height, which should be at least 3 centimeters higher than the driver's head when behind the wheel and wider than the driver's shoulders.
- The driver had to be able to get in and out without moving any moving element, including the steering wheel.
- Mandatory automatic start:
With built-in starter motor that could be operated by the driver behind the wheel.
- Fire protection:
In addition to the protection already provided by art. 125 of the C.S.I. was required the car had to be equipped with an electrical main switch or with automatic control, or be operated by the driver.
A separate (dual) braking system was required in such a way that, in the event of loss at one point of the braking transmission, the brakes continue to operate on at least two wheels from the same axle.
- Oil collection:
It was mandatory to install a device designed to accommodate any oil return through the crankcase fill port.
No oil supply is allowed during the races.
- All engine and oil reservoir filler openings were to be designed so that filler hole seals could be fitted.
Commercial fuel only as defined by the F.I.A. was allowed.
- Certificate of origin:
Every Formula 850 (F. 8½) car that appeared for a race was required to have a certificate issued by the C.S.A.I. that confirmed the origin of the basic elements.
The requirements were updated from 1967 to 1979. For example, the permissible dimensions and weight of the car were adjusted and there was more freedom for the manufacturers to choose parts. These changes may be discussed later in another article.