frost, i also understand your second post there, and that is why you need head shims. that happens often in glow engines because the glow plug is constantly "glowing". but by increaseing the nitro percentage and richening the motor you will increase compression for 2 reasons. first the more liquid in the engine equals more compression. this is demonstrated when you flood an engine and it locks up. since liquids are much harder to compress than gases then it makes more compression when there is more fuel. second, since there is higher nitro levels that means that the fuel will burn more rapidly with a larger force.