George k said:
Ben and Andy, congratulations on what looks like the perfect high performance saloon package, with the ideal usable shape power curve. No doubt a lot of this is down to the cams, and from the brief specs that you mentioned above you have gone for the holy grail of moderate period and high lift; the only thing that worries me is that this normally brings very high accelerations and closing loads. Have you yet enough experience of them to know whether this brings any durability problems? I am led to believe that this sort of profile can in some circumstances generate such high shear stresses that the oil film between the cam and follower starts to break down - perhaps because the engine is not revving to much over 7,000 this is not an issue - what do you reckon?
Regards
It certainly has been taken into consideration
Went into detail in another thread, but cant be bothered to find it.
Basically, alot of time was spent arranging a profile with gentle initial flanks and a nice acceleration curve that wont overdo what the std springs can handle. The BCD is about 2mm larger than stock, and 1mm larger than shrick, so with the profile run, you can see that things are very 'gentle'. With early cam tests on UK firms 'regrind' offerings, the bcd's were substantiall smaller than stock, and they would tap to high heaven because the hydraulic pivots would be at max extension and not be able to take up enough clearance. Add high acceleration rates, high clearances and the valves were effectively being beaten with a hammer and raw float/bounce, aswell as resonant harmonics were out of control.
The std followers are mini roller radius path followers, so shear forces on the rollers themselves are not high in any instance, however without a hydrodynamic wedge infront of the lobe as per a normal static face sweep area, it cannot be judged in the same manner.
Durability isnt an issue, for the cam, or the follower.