The industry standard for lpg blend is 60% propane and 40% butand but Australia has a roughly 70% to 75% propane blend as a majority amount of our lpg comes from the Bass Straight and is best left without a heavy butane blend. A good comp ratio for our lpg is around 9.5:1. Give or take bugger all. Too high and you will notice the pinging. 10.5:1 would be about as far as I would go. Another thing with lpg is to consider the timing advance. Timing characteristics between lpg and petrol are very different. LPG req more initial advance and less overall advance while petrol is opposite. Dry slow burn v's wet fast burn. Getting the dizzy sorted out is a major factor with lpg. With my straight lpg datsun I have a base timing of 18 deg BTDC with a total advance of 28 deg BTDC full mechanical advance. As dazza1200 pointed out 'a good ignition system is a must' LPG req a good strong 40KV spark reserve as LPG does not blend well with the oxygen.