Hi Garry,my engine has a No2 camshaft which is out of a very early engine not the later engine I have - any ideas why? and what are the characteristics of the different cam numbers
I had some discussion about the #2, #3 & #5 camshaft profiles a while back with Constantin. About all we know is that the #5 camshaft is used in all the 27HP motors with 4800RPM rev limit. Presumably, the cam profile allows for a greater air/fuel charge at the higher RPM. The #3 camshaft is found in early series 2 engines with Zenith NDIX carb rated at 24HP. The #2 camshaft is found in series 1 motors with Weber carb rated at 21HP and limited to 4500RPM.
I suspect that a compromise was made when going to the #5 profile to gain better high RPM performance and as such sacrificed a bit of low RPM torque as is usually the way with camshaft designs. Perhaps the previous builder of your engine had the same theory as I in this regard and preferred heavier torque at low speed.
Cheers,
Steve