Roller Rockers in Stock

[Paul Precht]

The Isky ductile iron adjustable rockers have no advantage over the stock Max rockers. Both measure around 1.47. I have two sets of these and still run the same 1963 rockers I got with a stock Max engine in 72, Paul.

[Jeff Lee]

Originally Posted by Paul Precht

The Isky ductile iron adjustable rockers have no advantage over the stock Max rockers. Both measure around 1.47. I have two sets of these and still run the same 1963 rockers I got with a stock Max engine in 72, Paul.

Don't forget your MOPAR buddies that also get to run the Isky parts as a replacement to their 318/340/360 engines factory equipped with stamped steel rockers. I think you would agree there is a considerable durability advantage in using those Isky's over stamped rockers.

[Alan Roehrich]

Jeff, Holroyd's rockers are STOCK GM, the studs and adjusters are similar in material to the ARP rocker studs.

We can get by with the 7/16" stuff, there are even some fast cars still using 7/16" rockers. What we broke 2 years ago at Gainesville was an ARP rocker stud, it broke at the base of the threads. I was going to upgrade to the ARP Pro Series studs when a friend turned me on to Holroyd's stuff.

The rockers themselves will still fail the same as the 7/16" rockers, ask a couple of the real fast guys.

If you are willing to replace the rocker studs often enough (the ARP Pro Series studs are $100 or so) you can run the stock diameter studs and rockers. You MAY lose a little to deflection.

NHRA allows all engines to run aftermarket studs, and even convert to screw in studs when they were not originally equipped.

Some big block Chevy high performance engines came with 7/16" pushrods. We (as well as most I know) currently use 7/16" straight pushrods and GM guide plates.

Again, I'd LOVE to see a solution for the rocker problem so that guys with the less popular stuff could go buy good parts for a fair price. I DO NOT want to see cars parked.

However, allowing roller rockers will absolutely bring about serious unintended consequences, for the reasons I outlined earlier.

[SSDiv6]

Originally Posted by Alan Roehrich

However, allowing roller rockers will absolutely bring about serious unintended consequences, for the reasons I outlined earlier.

As long as they do not allow shaft type rocker arms in applications that were not OEM configuration, and they do not allow stud girdles, then there will not be any measurable gain in power, just reliability.

[Alan Roehrich]

I do not agree. If you take an engine equipped with stock shaft rockers and large diameter lifters, and replace the stock shafts and rockers with 8620 or 8740 shafts and big roller rockers, you can EASILY exceed what can be achieved with stud mounted rockers and no stud girdle, even WITH roller rockers. Otherwise, there's be no market for stud girdles, and there'd be no shaft rocker conversions.

[SSDiv6]

Originally Posted by Alan Roehrich

I do not agree. If you take an engine equipped with stock shaft rockers and large diameter lifters, and replace the stock shafts and rockers with 8620 or 8740 shafts and big roller rockers, you can EASILY exceed what can be achieved with stud mounted rockers and no stud girdle, even WITH roller rockers. Otherwise, there's be no market for stud girdles, and there'd be no shaft rocker conversions.

Alan, there are only a few applications that use the shaft rockers: Mopars, Ford FE and Buick. The Mopars, both big block and small block, and the Ford FE's, are already running aftermarket adjustable iron rockers made by Isky or Crane. They are not stamped rockers like most OEM configuration. For Mopar applications, you can get a hard-chromed shaft, made of a heavier material that will not flex, at your local Mopar dealer over the counter. The Isky and Crane ductile iron rocker arms do not flex.

By the way, both the Mopar and Ford FE's, already have a big OEM lifters, and they also are fast.

[Alan Roehrich]

I'm well aware of that. In fact, going back a few years, I was working on a Tunnel Port in a Shelby, and I learned VERY quickly about the strength difference between the stock replacement style rockers and the aftermarket roller rockers. There is a major difference, at least in my experience.

[Dwight Southerland]

Originally Posted by Alan Roehrich

Jeff, Holroyd's rockers are STOCK GM, the studs and adjusters are similar in material to the ARP rocker studs.

However, allowing roller rockers will absolutely bring about serious unintended consequences, for the reasons I outlined earlier.

Alan -

Your argument on the basis of logic whows a bias toward yourself, as well as most of the arguments presented here. Just because "Holroyd's rockers" are available from GM doesn't mean anything; GM is more capable of producing high quality race parts than aftermarket suppliers (more budget, bigger staff, bigger economic base to absorb R&D costs and a product that will make no profit.) Before the new rule revision, you BBC racers enjoyed an advantage of being able to cross breed some factory race parts that were never specified as even replacement parts for the engine combinations you are racing. So it is with most engine combinations, especially when you get into the higher classes that require engines that produce enough power and RPM to exceed the capability of OEM, assembly line specified parts. Allowing roller rocker arms at this point willl make so little difference in the playing field (unless you are afraid of some of the engine combinations mentioned that use shaft rockers) and will provide a way to eliminate breakage for you and everybody else.

It's the open valve spring rule and the elimination of requiring stock duration that is killing the budget for stock cars, not roller rocker arms or big push rods. If you had to retain stock valve spring pressure, rocker arm breakage is not a big issue, and there would be no 8000 RPM+ engines.

[Alan Roehrich]

Dwight, we both know full well that the rockers Clark Holroyd sells are plain old stock rockers originally designed for truck engines, during a period where Chevrolet didn't have much interest in racing, and certainly not big block engines in drag racing, at least outside of Pro Stock. Clark Holroyd just has studs and adjusters made anyway, he just happened to see the rockers on a replacement engine, and thought "hey, I could use bigger studs with those". GM didn't design a "race piece" and then sit back and wait for Clark Holroyd or someone else to "discover" them.

No, a lot of the 396, 427, and 454 engines did not come with 7/16" pushrods and guideplates.

I agree, the open valve spring rule is what has caused this. We cannot "unring the bell", they'll never go back. The duration rule didn't cause this, because the shorter duration you're allowed the more you try to accelerate the lifter within the duration allowed. If you had the open valvespring rule without the open duration rule, it'd be even worse than it is.

The roller rocker rule is just another step towards a slippery slope, and it will make the playing field even less level than it is now. And where do we stop?

I have a friend that makes roller rockers, if the rule comes in, I can always have him make me a few sets that use 9/16" studs and be right back to where we are, because we aren't breaking rockers. But then I go from a $65 set of rockers to a $400+ set of rockers. And again, where does it end? Bigger lifters for all? Roller lifters for all? No lift rule?

[Alan Roehrich]

One more question. Who are we going to get to police the trick custom roller rockers that have the pushrod cup and the roller tip moved around in relation to the fulcrum? Got any idea what kind of games you can play by altering that relationship? Do those of you campaigning for roller rockers realize that rocker arms are NOT constant ratio?

Okay, so that was more than one question. And yes, I know that NHRA can easily check for maximum lift. But how often do you see them do that? Besides, it's not more maximum lift you get by playing with the relationship between the pushrod cup, the fulcrum, and the roller tip. It's the ratio on either side of maximum lift. You can radically alter the lift curve. It's easy for the shaft rocker guys to experiment with and play with, just shim the stands, or shorten or lengthen the pushrod, and then plot the lift curve again. Go ahead, see what happens.

Oh yeah, how many sets of trick rockers do you want to buy, and how many trick cams do you want to try to take advantage of them? Think about THAT before you decide how much cheaper and easier you think roller rockers will make things.