Realisticly the benefit from increasing the rocker ratio on a stock engine is marginal at best. Normally the ratio increase is benefitial only when more lift is required to take advantage of better airflow at higher lifts. The trend lately is to reduce the lobe lift and increase the rocker ratio to get the desired valve lift.
The best way is to flow the cylinder head then grind the cam for the duration/lift, you need. Just changing rocker arms won't show an increase in performance if the cylinder head can't use the extra lift. However, in my case Dema Elgin had to gring the cam down to the very core diameter to get the lift I needed, even with the 1.85:1 rockers. Trying to get 0.620" lift on these old engines is pretty difficult, especially with a flat tappet cam.
Does anyone have any flow numbers on the 235/261 heads? From talking to Kevin at the shop the head isn't conducive to porting of a serious manner. Water is pretty close and the short-turn is bad.
It looks like I have some research to do. The GMC is pretty straight forward and I have a working model, etc to work with.
Ron
