In every Mini Cooper ’S’ and in the 650 cc and 750 cc range of BSA-Triumph motorcycles, the exhaust valve guides were manufactured from Hidurel 5.
In extracting such a high performance and high power from the relatively small engines of these cars and motorcycles, the high temperatures of the exhaust gases impose considerable thermal stresses on the valves and valve seats. To preserve and protect both, rapid heat transference is necessary besides other essential mechanical properties in adjacent material.
Hidurel 5 (UNS C64711, DIN 2.0855, DTD 498) is a high strength bronze with high thermal conductivity which, used as valve guide material, provides a ready path for heat to flow away from valves and valve seats, and so helps maintain port seal efficiency. It also has good wear resistance anti-frictional qualities in operation with heat resisting valve steels, and its matching co-efficient of expansion permit closer working tolerances essential to optimum engine aspiration.
The value of Hidurel 5 in this application was proved by many wins on the international motor racing scene in the late 1950’s and prepared its way for widespread use on the roads of the world in the 1960’s.