im running a stock 305. and im looking at changing over to 1.6 roller rockers. now my question is will i be able to run 1.6 with the stock valve springs? and if so will the valve hit the pistons?

 

The stock cam is so small, and has such short duration, that the extra 6% lift and couple degrees effective duration from the higher ratio rockers should not cause any interference, nor stress the stock springs any more than the stock rockers would.

And you'll probably notice very little difference in performance, especially if the rockers are stamped stell like the stock pieces and they are installed over the stock springs. Valve float would still occur at about 4,500 RPM and the engine will act just about the same as before.