[Tatey]

From working as a student design engineer at triumph motorcycles for the past 12 months on powertrain the reason for going for ali and plastic are to save weight, and for plastic to save cost.

There will be heat transference between the head and the inlet but it will be within the working limits of the material used, cold air is drawn through the inlet manifold which will help cool it, the inlet manifold would normally get to about 80-150°C depending on if the engine has a steady stream of air moving over it or if it is in a heat soak phase e.g. if sitting at traffic lights after an aggressive run.

Aluminium has a higher specific heat capacity when compared to steel and will therefore conduct more heat, hence why aluminium is used for heat sinks.

There will be no real issues when using steel/stainless steel other than the potential for galvanic corrosion to occur between a steel and aluminium interface if the head is made from aluminium. However a gasket between the two should prevent this from occurring, or at least minimise its affect.