Which ones would give you the best geometry with iron heads stock length valves? The H/S's seem to ride from the center to outside edge. RB/906 heads.

I put a bunch of pictures of rocker arm setups in my Mopar big block book just because of this issue. The HS rocker arms are the longest rocker arms while the Cranes are the shortest. I think the old Isky nodular rocker arms worked really well but they are hard to find these days. Personally I'd probably use Hughes rocker arms since they've spent a fair amount of time sorting out the geometry and oiling issues. I used to use RAS rocker arms on all of my builds but they fell on hard times.

No way to tell without trying both.
I just read Vizard's comparison of 20 different BBC rockers, and even the ones that looked really similar had really different lift vs. rotation patterns.

Exactly. Whenever I'm building a new combination I line up a selection of rocker arms and see which ones are going to work the best.

I think you are confusing alignment with geometry. That being said, I would guess that the ductile iron will be better for both.

Bingo! But, any of them can have correct valve side geometry. Just not "bolted on".

Thanks for the input. I didn't do a very good job wording my question. BSB67 I have seen you running @PRP. I'm going to see if i can round up some crane or isky d i rockers then do a mock up.

So Andy, are these Isky rockers a good choice for a 505" Indy head
street stroker? Don't have a clue as to their ratio, but could send them
to RAS if that's a good thing to do.

I'm not Andy but those are the early, good, Isky rockers with the good valve stem wear pads welded on to them I wish I had a complete set of them now to use without having them bushed snd accurised right now

Thanks Cab, thought I was replying to Andy, but appreciate your info as always.
Do you think these are a better choice than Crane rollers? I was thinking of selling them, but if they're a good choice, maybe I should use them.
Got the matching pushrods, but they're for 906's.
Thanks again for the info.

I like and have use the Isky, I don't know about the new Crane ductiles yet so no real feed back on them. I have check lot of different rocker arms at the retainers to see if the ratio are correct or not, many are not including some of the very hi dollar race rockers I would check those on a motor with a set of weak checking spring to see how close they ALL are to being 1.5, or whatever they check out to be I have had RAS rebush and accurise several sets of ductile iron rockers in the past, I have a set their now that he is having a really hard time getting them to change to 1.6 ratio I'm going to send him some more and hope he can complete one set of 1.6 and one set of 1.5 form all the ones I sent him

Those are the same rockers I have and I highly recommend getting them done at RAS if they still are doing it. I have their shafts and hardware too and it really is a bullet proof setup.
Gus

Thanks & if RAS can make these 1.6, how much would they charge to accurize & rebush them?

I had them bushed,blueprinted,oil redirected,bodies narrowed, new hardware,and thick wall hard chrome shafts for about $525.00 with shipping I thought it was a bit much until I got them on the engine and everything checked out perfectly. I really like how they fit the shaft and feel more precise when I set the lash.
Gus

Nice pic & price seems pretty good when you consider a new set of crane ductile rockers alone are $500.

Sorry to hijack the op's thread & here's the website for what used to be RAS to have the ductile's upgraded as was said. http://www.rockerarms.com/

It's a lot worse than you think (and I've been researching the subject for 40 years).
Vizard compares rockers with the same nominal ratio for actual ratios at many different lift points, then the average lift. The results are nothing like what I expected with no pattern.
In his opinion, high ratio right after IVO (to jump-start intake flow when the piston is nearly stalled and vacuum is low) is the most important, and it doesn't follow any metric that he discloses.

I'm probably missing something, but do you mean IVO?

Yes, ooppsss, thanks! Senior brain fade.

I would expect that from him....take advantage of the significant negative pressure from the open exhaust valve at overlap..... I would guess.

So either mess with faster ratio, or change the rocker geometry to move the IV off the seat further per degree in overlap.