I think it's impossible. There is a way to check lift if you don't have the cam specs, but I don't think you can do anything with the cam in the motor. If I'm wrong, someone will jump in. As easy as timing covers are to R and R, you'd be better off to do that unless you water pump and ect are on the motor.
I suppose you could measure lift at the lifter, multiply that by rocker arm ratio, will equal valve lift i.e: .320" x 1.5 = .480" lift at the valve. You could probably get a pretty accurate reading with a machinist's rule or better yet a magnetic based dial indicator. As far as duration I assume you would probably need a degree wheel.
You can measure lift relatively accurately at the top of the valve stem. Remove valve cover and measure from a stable point to the top of the valve stem when the valve is closed and then again when the valve is fully open (valve stem down as far as it goes). The difference is valve lift. Divide this number by the rocker arm ratio (probably 1.7) and you have lobe lift.
I have tried to get approximate duration by marking off degrees on the balancer and then rotating engine while watching one intake and one exhaust valve open and close. It will only give a rough approximation and remember that most duration numbers that are meaningful are "duration @ .050" lift". It is pretty difficult to measure when your valve is open .050" and closed to within .050". There are probably better ways and I'm sure someone will chime in.
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