There has been a great thread about Yella Terrra rockers but I didn't want to hijack it so I thought I would open a new one.
Rocker Arms are very interesting and seems there are many different designs: ratio differences, trunnion bearing size/designs, roller tips, etc. to pontificate. My Engine build will be a pretty basic 351C using 71 4V Closed Chamber heads, flat top pistons, a cam with a tad more lift than stock, .550-.570". I don't expect I will need massive springs to control my valves, the valves won't be titanium. I will likely take Georges advice and go with the Pac Racing 1900 spring although I have been considering various Beehive springs just to lower the weight of the retainer. I'll probably limit my rpm's to 6,000-6200. I'd like to stay under $400 for rockers which seems very doable. But if I have to go with studs, guide plates, and machine the pedestals, that's another story.
My main questions involves materials rocker arms are made of and some design differences. First the metal they're made of. I see Aluminum on most the fancy ones, but I also see a few made of steel or stainless. One that has peaked my interest is the PRW Pro Series Stainless Steel Rocker Arm 0246003 (another Pantera owner is using them and he likes them). Obviously they're made of stainless which is described at: "manufactured from lightweight, premium quality 17-4ph stainless steel—a superior alloy high in nickel and chromium". I'm one of those people that would rather sacrifice a little weight (maybe a few grams per rocker arm, compared to aluminum) and go with something a bit stronger for longevity/reliability reasons, than go with Aluminum if it compromises reliability. I look at what Ford put in the stock 351's and the Boss motor, it was steel with a fulcrum with no bearings or nose rollers. They worked great, and gave great service and longevity. Were they optimal, probably not.
My second observation is the size of the trunnion bearing. Most seem to be with smaller bearings (Scorpion, Harland Sharp, Comp Cams, Crower etc), others like the PRW mentioned above (picture below) the larger trunnion bearing adds stability to the rocker arm motion and durability.
Third, my 4V heads probably have had the head face machined, and the spring seats were machined for double springs and a damper, but the pedestals are still stock using a 5/16" bolt. Most of the rockers will require going with a 7/16 stud which adds to adjustability, or I can go with the Scorpion Roller Rocker 5/16 bolt down rocker and just change out to the ARP Chromoly bolts. The Scorpion route is quite appealing just to shorten the process and get it done. How big of a deal is it to have adjustability? The reality is I want daily/weekly driver reliability and don't want to be tinkering all the time.
As always I appreciate the input of this group! And maybe someone else has the same questions.
