Originally Posted by fraser19
so it was mentioned to me that mabey i should invest in some rockers & rollers. What exactly do these do? Were can i get some? What kind of gains should i expect? i have a 4.0 sohc
On engines where the cam is in the block (ohv) you can usually sneak in a shorter "rocker arm". What this does is to open the valve a little more with the same cam. That increased valve opening allows more air in.. and there-for you can make a little more power.
However a OHC (over head cam) engine has the lifter -to- cam -to- valve distance fixed. A different set of lifter won't open the valve any more than it already does.
You could maybe get a lighter set.. or maybe one that will give less friction. But you can't gain any mechanical advantage and open the valve any further.