Group A features engines that are mildly restricted to ensure a reasonably equitable playing field for all competitors. Restricted in engine size to 412 cubic inches utilising cast iron blocks and cylinder heads with a maximum of eight cylinders.
The cylinder heads are restricted to two valves per cylinder. A wet sump lubrication system must be used. Induction is by a single 4-barrel carburetor of restricted size, and fuel must be commercially available petrol or Avgas. A V8 Group A specification engine is capable of producing in excess of 630 horsepower.
