Okay guys onto the black art of engine tuning ! How does one actually go about tuning an engine by shimming it ? What do you gain/lose etc. I am talking particularly about performance on track - not about shimming it to match nitro percentages or to decrease/increase compression to solve pre-detonation or other problems.

Also does anyone know what nitro fuel % the Novarossi RS and NS .12 series came originally shimmed for ?