Many of our customers have expressed concern about using unleaded fuel in their twincam engines especially since the octane rating of unleaded fuel was lowered.
It is true that an original, unmodified, Lotus Twincam cylinder head will eventually start to suffer damage if run using lower octane, unleaded fuel for a prolonged period of time. However the problem can be rectified.
Since the early 90’s we have used valve seat inserts with a raised chromium and nickel content as well as bronze Colsibro valve guides. With this change of seats and guides our engines are happy to run using unleaded fuel.