set the engine at about 10*btdc and check for how much valve travel you have at that point and then plot it out till about 10*atdc---for a bit the clearance will be getting smaller and then it will get larger---then apply that info to the cam you now have and you will have an idea----of course cam timing to the crank, lobe overlap, rate of open/closing, etc, etc all will effect it---but with the right rates you could probably go to .650 with your springs/valves/retainers