Hughes Engines Tech Center: Between A Rocker And A Hard Place


Not all performance parts are made equal. Hard as it may be to believe, sometimes flashy words or phrases are used to imply enhanced ability, even though that might not always be the case. With so many variations of rocker arms available, it can be difficult to discern which is actually best. The Hughes Engines Tech Center is quick to clear up why aluminum rocker arms like their 1506 models are generally a good bet:

We have had calls inquiring about stainless steel & iron rocker arms and would like to state our position. Stainless steel & iron are good, strong material for rocker arms and they claim they are stiffer than aluminum rockers. However, the aluminum dampens the harmonics better than steel. What the stainless steel people talk around is the fact that most do not have any bearing material in the bore. This means that you have a very hard shaft and a very hard rocker bore interface. This is not a good situation. 

Normally one part, usually the bore, has a softer material which acts as the bearing. For example, consider engine bearings. In all engine bearings, the shaft is extremely hard and the bearing material is soft.

As a matter of fact, most engine bearings have a very thin coating of babbit on the surface. This babbit coating is very fragile and as you know can be damaged very easily. These types of bearings have much more stress and pressure on them than the rockers and they live for thousands of miles.

Two hard surfaces against each other is not a good situation. So, what can happen? Check out these pictures! These photos are of some stainless rockers and shafts. You can expect the same results from iron. 

The rockers and shafts are badly damaged. No, they did not run out of oil. If they had, it would be indicated by a change in color on the surface of the metal. What actually happens is there is no bearing surface and the two hard surfaces micro-weld themselves to each other then break loose and then repeat this scenario over and over causing a snowball effect until they look like these photos or seize together. Not a pretty sight!

If the stainless rocker were bushed with a bronze or “plastic” bushing they could live. It is also interesting to note here that many of the NHRA and other pro racers run aluminum rocker arms. Some of the import stainless rockers have bushings, but they have other issues.

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Kevin Shaw

Kevin Shaw

Editor-in-Chief – kevin.shaw@shawgroupmedia.com Kevin Shaw is a decade-long powersports and automotive journalist whose love for things that go too fast has led him to launching Mopar Connection Magazine. Almost always found with stained hands and dirt under his fingernails, Kevin has an eye for the technical while keeping a eye out for beautiful photography and a great story. He's also the co-author of "The Chrysler B-Body Restoration Guide."

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  1. Avatar
    Mike66Chryslers 8 April, 2020 at 14:49 Reply

    I’ve read before that aluminum rockers aren’t recommended for street use because aluminum is work hardenable. The article states “the aluminum dampens the harmonics better than steel” without expanding on that statement at all. They are implying that the rocker body flexes slightly.
    This flexing will eventually lead to the rocker body cracking.

    Unlike a race engine, a street car may not have the valvecovers off for 10s of thousands of miles, so your odds of inspecting the valvetrain and catching this before catastrophic failure occurs are small. This article does nothing to dispel this worry.

    • Kevin Shaw
      Kevin Shaw 8 April, 2020 at 22:53 Reply

      Do aluminum heads “flex”? No, but properties in aluminum allow for better ABSORPTION and DISPERSION of harmonics and heat. Aluminum rockers absorb (ie. dampens) harmonics better than steel because the atomic structure of steel is far more rigid than that of aluminum (hence why aluminum is less brittle or prone to cracking as steel).

      Factory-built cars were equipped with stamped steel rockers because IT WAS CHEAPER. And you may recall that people regularly took their cars in for “tune ups” where carburetors were adjusted, ignition timing was checked/set and valves were re-lashed. These were very common service items.

      And considering that Hughes Engines is addressing performance machines – not lazy or stock builds – you can rest assured that the valve covers will be off well before any rebuilt classic reaches 10K miles.

  2. Avatar
    Ben j Nokleby 10 April, 2020 at 20:08 Reply

    Buy Harland sharp and drive a bigblock 100,000 miles without doing anything. They are aluminum and I’ve never seen a broken one. That’s wrong, I saw one that broke after 20 years on a bigblock chev that had a roller cam with .850 or more lift and a bizzare amount of spring pressure.

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