Ductile iron rockers vs. aluminum roller rockers?

Has anyone seen a performance comparison done between the two types of rockers?

It seems the norm to put high-zoot aluminum race rockers on an engine that is driven on the street anymore and it always make me cringe.

I have had a set of Ductile iron rockers on my car for 30 years. race car. has a 640 lift cam in it now. I am building a new engine now and I bought new set of Harlem sharp rockets for it. We will see. I hope I am not disappointed.

Where would you even buy a set of ductile iron rockers these days ? That's why aluminum is the new norm !

Near the end of the Crane ductile iron big block rockers being something that were actually “available”, they were $500...... without the shafts or any hold down hardware.

Yeh....... no thanks.

The last set I used that were reasonably priced was in 2005, and on that set the adjuster screws failed on the dyno........ so another close to $100 was spent to put some Smith Bros. adjusters in them.
All said and done...... had pretty close to $500 in that rocker set up.

I’ve also seen plenty of those iron rockers that had some fairly serious galling going on with the shafts.

There isn't any difference in performance but steel should outlast aluminum by a long time. I have one engine with Comp steel rockers that runs 9's in a B body. Those rockers have held up well for the last 4 seasons.

I regret installing Crane Alum rockers on a mild SB decades back, with no fulcrum bearings or bushings. They looked cool.
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As mentioned below, I used new I thought quality shafts in my application that left me rather unsatisfied with the galling.

Why aluminum?
1. lighter (actually the difference in reciprocating weight is limited to the ends, isn't significant)
2. cheaper to make
3. cheaper to alter to fit another application
4. you must buy them again or risk failure
5. shiny!

I think a lot of the galling had to do with guys using them on used or crappy stock shafts. In the early '70's I bought an Isky kit that came with cam, lifters, pushrods and rockers - but no shafts. What the hell did I know ...I stuck them on the original shafts! While I didn't have any galling issues (luckily), when I took them off after the first season I noticed they were hard to remove (tight around each bolt hole). That's when I realized stock shafts needed to be replaced for any performance application. In those days TRW made a pretty decent, inexpensive replacement shaft. I liked the hardened tips on the Iskys, I've seen MANY cranes that were badly worn at the valve tip. To this day I'd buy a used set of Iskys in a heartbeat if I could find them (reasonably priced).

In most cases steel is better. The Comp steel rockers are pretty good from what I've seen. The only time I've heard of an aluminium arm being better was on a Comp Eliminator engine, they swapped the intake arm from steel back to an aluminium arm, and it cleared up a valve train issue they were having.

The aluminium arms are easy to produce typically, the extrusions are probably used by many different companies as well.

I sent my ductile rockers to RAS (now RAU) and had bushings installed. They'll blue-print the ratio for a few bucks more. It included undersize banana grooved thick shafts and hold-downs. I have another set with some light galling that will be sent in to be bushed, or I'll get their stainless roller tip set for about $1k.
DVORAK Machine offers a do-it-yourself kit.
http://www.dvorakmachine.com/rockerarms.shtml

How much for the blue printing? They quoted me as follows: Total price for the complete assembly: (Hard chrome plated shafts, bronze bushings, re-face contact tips, steel hex hold downs and spacers kit with shims)
$549.00 + S/H.

I don't know what they charge for blue printing the rocker ratio. It's been about 10 years since I had the work done. I didn't have the blue printing of the ratio performed. I didn't think it was important at the time. It's really something for someone whom needs valve lift to be exact such as a stock eliminator engine. Mine are pretty close, but not perfect in rocker ratio.
I am super happy with the quality of work.

I wont use alum rockers in anything resembling a hi perf engine with decent spring pressures.....seen em break too many times.

I had RAU rebuild and bush my 273 rockers, touch up the rocker pad, hard chrome the shafts, spot face and install locknut adjusters and threw in billet steel hold downs.

Thats about what I spent on my Isky rockers when I sent them to RAS about 8 years ago maybe I love them and I'm currently running them with a 620 lift SFT cam.
I only lash my valves spring and fall and they always are dead on.

both times i used RAS and RAU I was disappointed and over charged from the original quote on both time and money NO MAS
I've used a bunch of Harland Sharp aluminum roller rockers on many different motors for a long time now with no bad results, current bracket motor has 840 Lbs. over the nose with 325 lbs. on the seats with Manton series 5 7/16 pushrods, pulls hard up to 7300 RPM with no issues of power dropping off
I'm going to try shifting it at 7500 RPM this year, raising the low gear shift RPM last year from 7000 RPM to 7300 made 2 MPG increase in the 1/4 mile with almost no ET gain, 8.862 at 148.?? MPH shifting at 7000 RPM. 45 minutes later in the other lane shifting at 7300 it ran 8.866 at 150.?? MPH

Any idea if these work with stock valve covers?

The Crane ductile iron ones do.

Sometimes you have to drill holes in the baffles right where the adjusting screws are.

I use stock 68 chrome 383 valve covers on my Dart with a set of those black rigid Felpro gaskets doubled up to clear the adjusters. I adhered two gaskefs together with ultra black and used longer bolts to ensure proper thread engagement.

You can't buy cheap aluminum rockers and expect them to last very long w/ big cams and high spring pressures.

Thanks for the pictures.
What wall thickness are the bushings?

I miss the old Isky rockers that I used with the Max Wedge heads and solid tappet cams. Never had any problems. Switched to Indy 440-1s. Only rockers available that i know of are alum. So it's T&Ds

Jesel, T&D and maybe Harland sharp are making steel rocker now

I ran 273 iron rockers on my 340s for years and iron ones on my W2 heads ,the biggest cam I used was a 627 lift roller and never had a problem, replaced one adjuster after many years. I will be using them again on my under construction/ rebuild W2 head 363.

We have a set of HS that have been in use since the 70's. The 1st three engines ran any where from low 10's to mid 11's They have been on my brothers GTX since 2002. Street strip car 500-1000 miles a yr.

Nice if there were some math to calculate time X stress to failure for aluminum rockers. We know most of the factors, but how much value for each?