3.12. Where advertising is allowed on windscreens it must not obscure the driver’ s vision nor cover more than one third of the depth of the visual area of the windscreen.
3.13. The fitting of mud flaps of a flexible material of 4mm minimum thickness behind each wheel extending to a minimum of 40mm each side of the tyre tread and to within 80mm of the ground when the car is unoccupied is mandatory.
3.14. Towing eyes of adequate strength and size must be fitted to or carried for fitting to the front and rear of the Vehicle. They must be painted a distinctive and contrasting colour.
4. Engine 4.1. Must comply with the following specification and actual capacity limits: 4.2. Production Car Engines:
a.
b.
c.
d.
Petrol engines with a maximum of six cylinders forced induction up to 2000cc with a 34mm restrictor or up to 2500cc with a 32mm restrictor and diesel engines with forced induction up to 2500cc with a 37mm restrictor.
Naturally aspirated with a maximum of six cylinders and more than 2 valves per cylinder – up to 3000cc.
Naturally aspirated with a maximum of six cylinders and a maximum of 2 valves per cylinder – up to 3500cc
Rover V8 pushrod engines up to 4000cc utilising the original Rover head castings and limited to either a maximum of 4 carburettor chokes or a single throttle body and the original plenum chamber.
4.3. Metro 6R4 2500cc and 2800cc( Single Plenum) engines complying with ASN Specification exclusive to 6R4s.
4.4. Specialist Competition Engines:
a. Naturally aspirated. b. No more than four cylinders. c. No more than four valves per cylinder. d. Maximum capacity of 2500cc.
4.5. Production Car Engines with a maximum of 2 rotors:
a. Rotary engine equivalence 1.7. Forced induction rotary engines equivalence( 1.7. x 1.7.) = 2.89. b.
Rotary engines will be considered equivalent to 4 valves per cylinder petrol engines in respect of the maximum engine capacity including the application of equivalency factor a. above.
4.6. Forced Induction engines must be fitted with a restrictor at a maximum of 50mm from the extremes of the compressor blades. The restrictor orifice to be to the dimensions currently in force in FIA Appendix‘ J’. Where there are two forms of forced induction fitted the restrictor must not exceed the appropriate FIA Appendix‘ J’ dimensions. Provision must be made for fitting seals to the unit( s). A fee is payable for the sealing of turbo chargers.
4.7. Except for Vehicles accepted under Category 2 a Vehicle may be fitted with a different engine not exceeding 25 % increase of the capacity of the model when it was supplied as original equipment by its manufacturer.
4.8. The engine capacity of FIA R / GT cars complying with Category 2. shall be limited to the current FIA Regulations.
4.9. Historic Rally Cars that are fully compliant with Appendix 17 are permitted without a restriction on engine capacity in Stage Rallies.
4.10. Engine Oil Systems – Unless equipped with a closed loop system a Catch tank of at least a one litre capacity to be incorporated in the oil breather system.
Motorsport UK 2025 National Competition Rules Version 11
Chapter 13 Appendix 16- Special Stage Rally Cars 504