Re: rolla rockers for non efi 302w and other q's
Standard heads = push in studs (simple inteference fit threaded studs), screw in studs is where the standard heads have the stud holes drilled and tapped to suit 'screw in studs' also the mounting pad usually has to be machined down to compensate for the thickness of guide plates (assuming u going to an adjustable valve train with stud type rockers), if using guide plates then u will have to use hardened pushrods as the rocker to valve alignment is governed by the push rod rubbing against the sides of the guide plate. Valver springs and retainers always should be matched to the camshaft being used, and if any sort of dual/triple type springs are to be used the spring seats on the head have to modified also.
All of the above is included with most aftermarket heads (u will have to buy pushrods of course) so assuming rebuilding a set of stockies = not worth the time or effort as at this stage u still stuck w 300 hp heads tops and the money invested in these mods is not inconsiderable, then to make any sort of bigger power u will need to have the heads ported w bigger valves, also not cheap
rocker ratio is the way the rocker acts on the valve transmitting the cams motion, ie if the cam lifts .3" then 1.6 rockers = .048 @ valve with 1.75 rockers = .525" @ valve
also larger ratio rockers make the engine think the cam is bigger as it lifts the valve further and faster (has to go faster to acieve the higher lift in the same time). Bigger is better up to a point, it's all physics as the valve spring may have to become heavier to controll the more aggressive movement of the valve also the extra lift may cause coil bind (where the spring cannot compress any more due to physical contact with itself)
Shaft mount rockers are shaft mounted instead of studs and are more rigid and stronger, no need for a girdle
Adjustable valve train is always better especially if modifing engine for either hyd or mech but is essential with mech type cams to easily/quickly achieve correct lash.
If all this makes no sense (very possible i leave bits out) get a copy of ford performance (autobarn etc) it's a good read although behind the times now and will help with basic understanding of perf type engine assy's in general>