EM008 MAC ENGINE

A question on what fuel to use. Its got an Alfin barrel and alloy head, with presumably insert of sorts. Is normal unleaded petrol ok? Or will I have to put in a dose of additive? In the 1960's when I last ran the bike on the road, it seamed to go well on the lowest octane petrol, but that might have had some lead in it. Although I wont do many miles each year on it, I will drive it fairly hard, cos it's fun to do so. - Andrew Baxter, 24/5/2005

You won't need to use an additive to increase the octane rating on a normal MAC, the question is whether you need it to protect the valves and seats. Otherwise normal unleaded is fine for a MAC or MSS (though not for a Viper or Venom).
If you had renewed the valves in their original material and/or put in original non-hardened seats then in theory they would need a lead substitute to protect them from wear.
However, if you have not renewed them and they had previously done a good mileage on leaded petrol then they will be impregnated with lead and that will protect them for any mileage that you are likely to do.
I use this principle rather than an additive (if the bike doesn't pink), reasoning that if I ever do get wear then that's when I'll convert to seats & valves suited to unleaded - meanwhile no messing about with (expensive & fiddly) additives. - TW 24/5/2005