trust = doing this from memory I think it is = exhaust pipe cross sectional area x 3.4 = thrust in lbs for gasoline.
exhaust pipe length = diameter x 11 = length
combustion chamber diameter = cross sectional area of tail pipe x 2
combustion chamber volume = 25% of total engine volume
cone shape = 25% of total engine volume
Air intake = 50% of the cross section area of the exhaust pipe.
Reed valves should not open more than about .200". You can adjust the frequency of the valves my limiting how far they can open. If they open too far they beat them self to death. .010" thick reed valves work best.
Reed valve hole diameter should be limited to about .400" diameter if possible. When the valves slam shut they tend to bow down into the holes this causes the valve metal to bend and crack.
I have more information about how to keep valves from getting hot and how to make adjustable reed valves but no time to list all that now. I can successfully run my engine at 100% throttle static thrust for 40 hours with very little signs of the valves getting hot and no damage. If you switch the engine over from gasoline to alcohol thrust increases about 140%. Ram air will increase thrust too. Mixtures of gas/kerosene, gas/fuel oil, alcohol/water will increase thrust.