4.4. Exceptionally the ASN in its absolute discretion may grant a dispensation to use non-original parts and or parts from a different model and or parts from a later period provided that the use of these parts does nor confer any advantage in either performance or reliability. The ASN will give consideration to written requests from Competitors who can evidence that they are unable to source vital components.
4.5. Competitors will be notified by means of an ASN Official Bulletin of any part subject to dispensation and a full list of dispensations will be published on the ASN website.
5. Engine 5.1. Cylinder bores may be 60 thousandths of an inch oversize without affecting class eligibility. 5.2. Four-wheel drive vehicles fitted with forced induction are prohibited in Historic Categories 1, 2 and 3.
5.3. Forced induction is only permitted if by means of a mechanically driven super-charger, or by an exhaust driven turbocharger if fitted as original equipment by the vehicle manufacturer App. 16 Art. 4.2. a. Such Vehicles in Category 1, 2 and 3 will be classified as having an engine capacity increase of one third. Vehicles in Category 4a and 4b will be classified as having an engine capacity increase of 70 % and must be fitted with a 34mm restrictor at a maximum of 50mm from the extremes of the compressor blades. Vehicles in Category 5 must be fitted with a restrictor of dimensions in compliance with the current FIA Appendix K and will be classified by the corrected capacity as detailed on the FIA Historic Technical Passport( HTP).
5.4. Engines must comply with ASN silencing levels. Exceptionally and with the permission of the Chief Scrutineer those cars for which 5000rpm is inappropriate may be tested at 3 / 4 of maximum rpm.
5.5. Vehicles in Category 4 equipped with rotary engines will be subject to an equivalency factor of 2:1.
6. Safety
6.1. Vehicles must be equipped with a safety rollover bar in accordance with Ch. 7 App. 3 Art. 1 – 20 and 22 inclusive, and Ch. 7 App. 13 Diagram 45 a) or b). Dotted lines signify optional features.
6.2. Door bars may be of single tube, crossed tube or twin tube design Ch. 7 App. 13 Diagram 21( g),( h) or( i).
6.3. A single Diagonal Member is mandatory and a second Diagonal Member may be added to form crossed diagonals. Diagonals may be either installed across the Main Rollbar or between the Backstays.
6.4. Additional tubes for the mounting of harness shoulder straps are permitted.
6.5. All bars must remain within the confines of the Passenger compartment and must not be used as suspension pick-up point bracing unless the Competitor can prove that this was done in period to the specific model.
6.6. Vehicles in Category 4 must comply with App. 16.
6.7. Belt cutter( s) must always be carried on board during an Event. Both Driver and Co-Driver must be able to reach a belt cutter when seated with their harness fastened.
7. Wheels, Tyres, Suspension and Brakes
7.1. Wheels and tyres must be fitted in compliance with Ch. 8 App. 4 Art. 2 and Art. 4.1 of this Appendix except as follows: App. 16 to this Chapter Arts. 7.1 and 7.2 and 7.4 and 7.6 – 7.8 and 7.10 – 7.15 and must conform with the following:
a.
b.
For Categories 1, 2 and 3 the diameter of wheel may not differ from that originally fitted by more than 10 %.
For Categories 1, 2 and 3 the complete wheels( flange + rim + tyre) are free providing that they are housed within the permitted bodywork and that they do not exceed the following widths in relation to the cubic capacity of the Vehicle:
i. ii.
Up to 1150 cc: 7in Over 1150cc and up to 1600 cc: 8in
Motorsport UK National Competition Rules 2026 Edition 1
Chapter 13 Appendix 17- Historic Special Stage Rally Cars 508