Bill,


According to the MVVS head engineer, the engines can all be run as they come, on up to 5% nitro.

If you need to use up to 15%, add one head shim (a total of 2) and off you go.

The RPM gain from going to 15% with the extra shim is 100-200 RPM.

Make sure you use only fuels that contain plenty of castor oil (over 50%).

...Unless it is Cooper's and then you can use less.