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rotor housing dimensions

Detailed technical information. Norton Interpol 2. Classic. Commander. F1. F1 Sport.

Housings and rotors should ideally all be standard but if rotor side faces are damaged and need to be faced up or the housings having been replated and need surface grinding, the two standards Norton chose were 4 and 8 thou undersize.( A grade and B grade).

 STANDARD'A' Grade'B' Grade
Rotor housing width68.19 to 68.2168.09 to 68.1067.98 to 68.00
Air cooled rotor width67.77 to 67.7967.66 to 67.6867.56 to 67.58
Water cooled rotor width67.86 to 67.9067.77 to 67.7967.67 to 67.69
Apex seal assembly overall length68.13 to 68.1968.03 to 68.0767.93 to 67.97

Undersize components are marked 'A' or 'B' grade as required. Standard size components are not marked

Rotors are marked in the combustion chamber alongside the compression ratio and handing marks.

Rotor housings are marked on the flat area adjacent to the vacuum take off ( close to inlet manifold).

Housings are sometimes colour marked Yellow for A grade or Blue for B grade.

Engines built at the factory with undersize components used the same width on both sides. Engine numbers were then suffixed by A or B but many engines have been overhauled since, some now have mixed A and B grade components. Do measure eveything before reassembly. Mis- matched components is one of the reasons for premature engine failure.