At its recent teleconference, the Australian Rally Commission (ARCom) considered the feedback received regarding three proposals regarding the 2007 PRC regulations.

These three areas were as follows:

1. Post 1986 2WD freedoms
2. Substitute engines
3. Expanded Eligibility criteria

The feedback received was of high quality and was considered in its entirety.

The response to the proposals regarding additional freedoms for post-1986 2WD cars was overwhelmingly positive. Therefore the Commission has decided that effective January 1, 2007, additional freedom to modify engines of such cars will be provided in the following areas:

- A maximum of 1mm overbore (up from 0.6mm)
- Induction is free
- Exhaust is free
- Freedom to modify cylinder head ports by the removal of metal
- Freedom of inlet and exhaust valve and valve seat size, and valve guide material

Regarding substitute engines for pre-1986 cars, the vast majority of responses were in favour of at least that which was proposed, and the commission agreed that it should go ahead with the proposal for 2007.

A more complex response was received on this issue though, with some respondents wanting more choice in regard to the engines that will be approved. ARCom felt that this concept had not been promulgated for discussion and therefore it was not in a position to consider these suggestions. It was felt that potential existed for more modern engines to represent a cost increase, as opposed to the saving that the rule change is intended to realise for some rally competitors.

Unfortunately there was little feedback regarding contemporary, post-1986, cars and as such ARCom was not willing to at this stage amend the regulations to allow substitute engines for post-1986 cars.

The substitute engine guidelines for pre-1986 cars, the approval of which will be at the sole discretion of ARCom, are that the engine shall:

- be produced prior to 1986
- be produced by the same manufacturer as the original
- have the same number of camshafts in the same location as the original
- have the same number of cylinders and general configuration
- be made of the same material as the original
- be able to be fitted in the same general location as the original. No body modification is permitted to allow the fitment of the replacement cylinder block.

Applications addressing these criteria should be emailed to

It should be noted however that cars with substitute engines are not permitted the full range of modifications otherwise acceptable under Article 3.3(xxix) of the PRC regulations. The following modification limitations will apply:

• Capacity - A maximum of a 17% increase in capacity over the original/recognised engine is permitted, however, the standard stroke must be retained.
• Cylinder Head: Modifications may be made to the cylinder head and related components only in the following areas:
- inlet and exhaust ports may be modified by the removal of metal only
- inlet and exhaust valve sizes and valve seats are free. The minimum modifications required to fit these items are permitted.
- valve guides may be replaced by others of alternate materials.

Cars which suffer a capacity alteration with a substitute engine and permitted modifications must compete in the capacity class pertaining to their new capacity.

Also considered was the proposal to widen the eligibility criteria to include four seat automobiles, which may not meet the interior dimensions of a ‘Touring Car’ as defined by the FIA – a current requirement under Article 1.3.

Responses were positive toward this change and ARCom will make the necessary changes to the regulations.

There was some confusion about the future of 2 seat cars which are currently recognised under other PRC eligibility criteria, such as the Datsun 260Z. To clarify, there is no change to those provisions and such cars will remain eligible.

A number of other issues were raised in the correspondence received and these are intended to be considered in 2007, potential for future application. These included the following:

- application of the post-1986 2WD freedoms to naturally aspirated 4WD cars.
- additional freedoms for pre-1986 turbo equipped cars.

ARCom would like to thank those people who took the time to formally respond to the discussion paper. The feedback has assisted greatly in coming to a conclusion on the proposals, and perhaps identifying some further areas for consideration.

Get full, exclusive access for only $6.55/month.
  • Full access
  • Exclusive news
  • Store & Tour discounts

Show Your Support


Recent Posts