 4.2 hp a/c & 6.2hp w/c
Greeny has taken the words right out of my mouth.Well said mate!
With the Polini engines there main A/C 4.2 hp is basically an a/c engine that you cannot fit a w/c setup.The next jump is the Polini 6.2hp a/c and this is one setup that you can apply all w/c cylinders to,etc.
BZM call there engines the 420 and 620 cases.There are alot of reasons for HP outputs.Bigger carbs,different reed boxes,different cranks,different exhausts,etc.The difference that i have noticed that the Italian A/C engines are 40cc 4.2 hp or 6.2 a/c 40cc and now BZM have made a 50cc 5 port a/c engine.With the w/c engines they start from 6.2hp 40cc w/c all the way up to 50cc w/c 6 port engine.So in saying all this they have produced more out of the w/c than the a/c engines.Also what Dazza has said is spot on as well!!! Maybe if they built a 50cc a/c 6 port that might be a bit of a weapon!Hope i havent confused you all!
cheers danny | 
