[70rs/ss]

Billa, there is some friction as the solid tip of the rocker slides across the vave tip. This is the cause of guide wear over time as well as wear to the valve tip itself. I do not think a roller rocker is a 10, 15, or 20hp gain, but in conjunction with the roller cam, etc, etc it is a piece of the puzzle. As for big valves in the Head, I'd probably hunt down a set of Vortecs before I reworked another factory iron head, they just flow and work that much better (really once you get a set of modified Vortecs, {purchased from Summit or the like} you end up having $8-900 in a set of iron heads) and a Summit brand aluminum head only costs $900ish and comes with 2.02/1.60 valves. I like the stock head with a differnet spring to allow more lift, but beyond that I would get a set of aftermarket heads, as you put more $$$ into the Vortecs, aftermarkets come into the price range and offer more options. It is all a matter of what you want, if the parts and labor are not too high then you may be able to rework a used set of Vortecs and get what you want without breaking the bank. Without a flowbench you are kinda working in the dark and may actually hurt flow. As Billa said open up the throat and seats, and Backcutting to actually allow the bigger valve to improve the flow. I really don't think a 2.02 1.60 has a lot to offer on anything but a high RPM motor, or a big inch SBC. 1.6 rockers are a crutch to improve cam lift without swapping in a new cam. 6 of one and half dozen of the other, if a new cam is part of the plan just get the cam size you want and stick with a 1.5. I think Billa and I agree, I just like to add better parts as I can. Roller rockers are not a magic bullet, but along with a laundry list of other parts they can offer longevity, a little more power and allow for more peddle response with roller cam, better heads, etc, etc.