Spring pressure and rpm can be "ballparked" with enough accuracy to qualify the arms for the alplication by the cam specs given. IE. Is the OP in shaft mount territory or not.

I agree that the geometry can vary depending on the cylinder head and arm selection.

So, you've got nothing?
That's what I thought. :lolhit:

Someone define this.....no hijack intended, never mind I can see this coming into play with a bunch of after market parts that are being assembled for the first time, but when your going all OE parts in a valve train does this really come into play.

personally, I think anytime a valve train change is made a pushrod measurement should be made.

700sci with stage 2 upgrade with 50 hrs on my scorpions. I went with the opinion of a couple of engine builders that are using them them selves.

There isn't a set dimension from the center of the trunion to the center of the roller. Different manufacturers have longer or shorter arms. Some arms work better than others on different heads because of this.

I'm betting that the OP will be able to achieve good geometry with these arms on a relatively mild setup.

When the valve springs start getting larger in diameter and height due to more radical cams, getting arms to setup correctly becomes more challenging.

I'm thinking the Thead MT alluded to, is in regard to these variances in arms. Probably worth a search.

Last year, when I was rocker arm shopping, the Crane Gold rockers, were MIA. Everywhere. Nobody had them in stock. Apparently, production on them stopped, and rumor was, they were being outsourced. I always liked the cranes, but obviosly, if you cant get them, then that does no good. I then began really liking the option of a steel rocker arm.

One of the things I've seen , on some aluminum rockers, including my old Crane Golds, was the Trunnions split in two. The Trunnions on the steel rockers, like the Comps, or Crowers, are massive in comparison. I chose to go with the new Comp Ultra XD magnum rockers, based on some info I had got on them. Basically, they were a new and improved design, that alot of technology went in to. Lifetime guarantee against breakage is a nice feature as well. They must feel pretty confident in them to offer that. Another option they offer on them, is an upgraded Trunnion, if you were to decide to run 1/2" diameter rocker studs, instead of 7/16.

We all know steel has a much better fatigue life, and the weight savings isn't there when comparing to an aluminum rocker. Basically, I saw no benefit to the aluminum rockers over them, or the Crowers.

I simply chose the Ultra XD rockers, based on the fact they were 100 bucks or so less than the Crowers, and they were something new. I like new stuff to try.

Do it on a hot plate in oil 200* and let cool. You can watch the air come out as the temperature rises and oil will pull into all voids.

If I were buyng new today, I'd take a hard look at those arms you used MT.
Friend used them on a pair of 502 marine engines with edelbrock heads.

scorpian makes two different series of rocker arms for the bbc.race and endurance.the race series is a stronger setup and can take more spring pressure according to their website.i have used several sets of the endurance arms and had good results with hyd roller cams.i used a set on a pro charged build i did with a solid tight lash roller ,275 on the seat 600+0ver the nose.the engine sees a lot of 6000 plus rpm,it really should have a shaft rocker system on it.it broke an arm at about 25 hours.i had a replacement arm in two days with no charge to me.yes i bought them from bob madera and he got right on getting me a replacement as soon as i called him.in retrospect,this is really not the rocker i should have used on that application.if it breaks another one i am going to go a different direction.to sum it up,for a hyd roller setup they will last dam near forever and i will continue to use them for that application.i have not used their race series so i can,t say if they are good or not.