[racinjason2316]

There is no universal formula for figuring out wether your engine will benefit from the increased rocker ratio. Switching to the higher ratio does two main things- #1. lifts the valve faster (effectivly increasing seat to seat duration)#2. lifts the valve higher. If your cylinder head flows well enough to benefit from the increased lift, there is a good chance you will see gains. A lot of it is cam/head combination. Larger ratio's do tend to exaggerate any valve train geometry problems that you already have. Every engine is different. Some engines benefit from the higher ratio on the exhaust side, and some on the intake side. Even more some on both. The best way to find out is to test them on the intake side first, and if that gains power add the exhaust. I have seen engines gain 20 HP from the bigger rockers on one side or the other and then loose a few or gain nothing from the other side. Heck some Chevy's like to have a little more ratio on just the center exhaust ports. 1.5's on all intake valves and the four corner exhaust valves, and 1.6's on the center exhaust ports. The only way to know is to dyno before and after after every change. Usually the gain is not enough to feel "seat of the pants".
As for piston to valve clearance, with any aftermarket camshaft and rocker package the clearance should be checked initially. If you document how much clearance you had with the previous set of rockers, you can subtract the increased valve lift provided and generally figure the clearance. If it's close, dissasembe it and check it properly. Sure beats a bent or dropped valve. And figuring the gross lift is best done by multiplying the camshafts actual lobe lift (printed on every cam card) by the rocker arm ratio.