Comparison-60's 427so vs New 427so ?

[DMXF]

The choice of pad or roller tip is influenced by a number of factors and engine attributes. An assessment of valve scrub work vs cam rotation angle for your given design will reveal how effective the subject pad is for relative comparisons. Starting with a clean sheet of paper with today's technology, pads are typically complex splines to minimize scrub work (i.e. reducing it at higher loads) - which means old original rocker pads are probably not as optimized.

If an engine spends much of it's time at only maybe 2,000 rpm and is never taken to real high revs to where high spring pressure is not required, a roller tip is probably in its realm of being most beneficial. At this lower speed the roller tip may be predominantly rolling and reducing friction and therefore result in lower lateral valve stem loads (although even a pad would have much lower scrub work at lower spring loads). This may provide a very slight power and fuel mileage gain and increase valve guide life (a big problem with FE's) relative to an old design stock pad rocker, however the gains in power and mileage are probably very small and don't offset the increased cost and potential reliability issues, otherwise the car companies would have jumped on board long ago by retrofitting it in all passenger cars. Power increases that some manufacturers claim from installation of their roller rockers I believe is primarily due to a rocker geometry which results in greater valve lift at lower cam lifts (effectively increasing duration) - you may have heard of this aspect referred to as "mid lift" optimized rockers.

One of my big concerns was valve guide life, given the miles that can rack up in street use. I have previously run FE's for enough years to know the guides wear relatively soon with higher spring pressures. The solution I chose with the stock pad tip rocker was to apply special low friction coatings to the rocker shaft, stock rocker tip and entire valve (incl tip) to reduce friction to hopefully a benign level....and rocker to shaft bearing mode life should be accordingly enhanced.

Two other concerns are rocker strength and geometric ability to handle the valve lifts employed. In large part by keeping components light, I've been able to keep max spring loads safely below 500lb, such that with polishing I believe fatigue is not a major problem with the stock part. If you have much higher spring load, you will be forced into using an aftermarket rocker arm, which for the most part are all roller tip for the FE (excluding some excessively heavy pad rockers by Crane or whoever).

The pad tip can be problematic if you exceed the design operating lift parameters. Even though my cam profile is within the envelope of the top factory race grinds used back in the 60's, the rocker rotates enough at max lift for the pad to ride right to it's edge. Aside from undesirable point loading if gone too far, scrub can go up dramatically if the contact point reverses direction in this regime. The stock rocker looks ok to maybe .650" lift (pushing it), so if you have higher lift you need to reconsider options. By the way, I'm referring to actual net valve lift, not to be confused with lift erroneously calculated by using "1.76" times cam lift after lash. A custom pad rocker can no doubt be designed to encompass higher lifts and spring loads, although the cost would be prohibitively excessive for most people on a low volume basis. Aside from avoiding the expense of doing that, I'm happy I was able to maintain using original parts with my configuration.