Running a different ratio rocker will not change Idle characteristics.(you wont get a lumpy sounding cam) Intake/exhaust valve overlap (the amount of time in degrees of crankshaft rotation) where both valves are off their seats is what causes the rumpity rumpity sound of a performance cam.
If you have a 302, you've got 1.6 ratio rockers. Going to 1.7's increases the lift by about .030" The 1.7's aren't longer though, the cam side contact point for the pushrod is moved inward toward the fulcrum to change the ratio.
I am running 1.7s, and it does run stronger, but doesn't sound any lumpier. It just opens the valve about .030 more for a better fuel charge and exhaust discharge. Most of those 1.7s that I know of are roller tips, which theoretically should be a little cooler running, and might free up a tiny bit of power. (I will likely be corrected in the following posts...)
The roller tips don't make em run cooler, the roller fulcrums do. The fulcrums also free up about 10-15 hp. Nothing theorectical about it, these were benefits Ford found in experimenting with roller rockers for the 93 Cobra 5.0.
