QUOTE: "To be fair I should have mentioned when reporting the cam figures earlier that all measurements are at 1mm lift which is fairly normal practice for those who may be unsure."
Here in the States, it's always been duration at .050" lift from the aftermarket cam grinders, as that lift is about where effective flow starts past a valve. SAE has several different standards for measuring cam duration, and some car manufacturers - Chrysler, for instance - use something different from .050". Zero, .006" and .020" come to mind. (Zero is the instant the lifter starts to move and is popular with hydraulic lifter cams.)
Long design duration specs on a flat tappet cam have a fair amount of low and slow lift rate at the start, which is intended to take up the valve lash softly, so as not to pound the valve train pieces. Once the lash is taken up, the faster lift rate kicks in.
1 mm translates to .03937", which will give a slightly longer duration than the oldtime .050", but this extra bit of info tells us that the Triumph 790 cams are not all that bad, but that smogger ex. cam could be a little bigger. Going with the same grind on the ex. that the intake has would be a decent step up
Thanks for the additional info, Graeme!!
