ORIGINAL: vti-chris
I changed from 20%nitro to 30% and didn't use the extra shim cause the engine is already with very little pinch so it's OK i beleive to use the 30% fuel.
Well there is one mistake. The shim is there for a reason. It wasn't just a freebie they threw in the box but a HINT that if you read the istructions, you'd notice they tell you to fit it for 30%. The reason: TO KEEP THE TIMING RIGHT.
Your engine IS running with advanced timing, this will start off with pitting to the hea from preignition but will result in in a conrod or crank failure should you continue. No matter how the pinch is With 30% the volume of the chamber must be increased. It'll run cooler and should be happy with a P6 where you are.