Stud Mount vs. Shaft Mount Rockers

Stud Mount vs. Shaft Mount Rockers

Up until the mid-1950s, overhead valve engines used shaft mounted rockers. When Chevrolet introduced their high revving small block V8s with stamped steel stud mounted rockers, it opened the eyes of engine designers to the possibilities of stud mounted rockers. Ford and others soon followed suit, and stud mounted rockers became the “hot” setup for the time.

As rockers continue to evolve, the ongoing trends toward lighter weight and stronger ­designs will continue.

Stud mounted rockers started to show their weaknesses as engine builders made modifications to increase engine speed and power. The press-fit rocker studs had a tendency to pull out if the engine was revved excessively or spring pressures were increased too much. Some performance engine builders started pinning the studs to keep them in place, while others replaced with press-fit studs with screw-in studs.

As valve spring pressured continued to increase, it became obvious that the rocker arm studs were flexing excessively at high rpms. The fix was to install longer studs and to clamp a bar (stud girdle) across the top of the cylinder head to tie all the studs together.

This, in turn, required taller valve covers to accommodate the stud girdle. It also made valve adjustments more difficult.

Aftermarket roller rocker arms were also introduced to replace the flimsy and rather wear stamped steel stock rockers. The performance rockers featured a roller bearing center fulcrum and a roller on the valve end of the arm to reduce friction. These were a huge improvement over the stock rockers and allowed higher rpms with more dependability and less friction.

As racers continued to push the envelope, it soon became apparent that some of these stud mounted aluminum rocker arms were not strong enough to handle the valve spring loads and rpms they were being asked to handle.

Aftermarket shaft-mounted rockers were introduced as a means of stiffening up the valvetrain, and steel rockers became an upgrade option for serious high-dollar racing.

According to some manufacturers, changing from stud mounted rockers to shaft mounted rockers (using the same lift ratio as before) will typically produce 10 to 15 more horsepower thanks to increased valvetrain stability.

The advantages of a shaft rocker setup are that the shaft holds the rockers in better alignment, eliminating the need for a separate guide plate for the pushrods. This reduces flex in the valvetrain at higher speeds for better valve control. The position of the shaft may also lower the pivot point of the rockers slightly with respect to the valves and pushrods to reduce friction between the tips of the arms and top of the valves. The shaft can also supply oil pressure directly to the rockers to improve lubrication and reduce friction.

A shaft mounted rocker arm system is overkill for most street performance applications because such an engine doesn’t really need that level of stiffness and strength. But for racing, a shaft-mounted system can provide increased rigidity and reliability.

Supporting the rockers on a rigid steel or aluminum shaft means the rockers can’t deviate from their fixed location due to stud flex or vertical motion on the rocker stud. The stiffness provided by the shaft holds all the rockers in perfect alignment and allows them to safely handle higher loads and rpms. Shaft-mounted rockers also don’t require a slot cutout on the underside of the rocker body to clear a stud, so shaft rockers are inherently stronger.

Shaft-mounted rocker systems are available for many aftermarket performance cylinder heads. In many instances, it’s a simple bolt-on installation that requires little or no modifications to the head. Pedestal mount rockers are also available for many engines with stud-mounted rockers.

A pedestal mount system can provide many of the same benefits as a shaft-mounted rocker system but at less cost. Many of these are simple bolt-in installations but won’t perform at the same level as a true shaft-mount system in an all-out racing application.

 

A Recent Letter from a Scorpion Customer

I recently purchased a set of SCP3017 1.6F Small Block Ford 3/8 Endurance Roller Rocker Arms. I am very impressed. The machining and weight concept is superb. My nicely prepped SBF289 engine uses a solid lifter Isky FL358 camshaft and the gear shift point is 7,000rpm. Valve springs are Isky 6005 doubles with damper. This is a lesson for people striving for a very quick power producing engine. The SCP endurance rockers are lighter, twice as strong as my engine needs, and with 0.20″ lift tolerance to spare. Conclusion: This product gives performance security due to quality materials and manufacture, resulting in a definite performance and durability increase. None better on the market, and I’ve tried a few roller rockers over the years!!!!!!!!!!!!!

Lloyd Gilbert


Thanks Lloyd!  We’re pretty proud of the quality that goes into every Scorpion Rocker.

Chuck Layton

Quality Assurance Manager

Scorpion Racing Products LS Race Series Roller Rocker Arms

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The Best Money Can Buy – Made in America!

Simply the best American Made Rockers on the market today.

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So much pride goes into every one of our rockers.  We make everything right here in the good ol USA and we are so proud of the quality and craftsmanship that goes into each piece.

Scorpion Tech Support

MONSTER JAM Ocala, FL – Bubba Raceway Park

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Apr 22, 2016 – Apr 24, 2016

Featuring: Bounty Hunter driven by Jim Creten, Scarlet Bandit driven by Dawn Creten, Carolina Crusher driven by Gary Porter, Monster Mutt Junkyard Dog driven by Dustin Brown, Xtermigator driven by JR McNeal, Ice Cream Man driven by Roy Pridgeon, Grave Digger driven by Charlie Pauken, Soldier Fortune Black Ops driven by Tony Ochs

Scorpion Shaft Mount Rocker Arms = Race Proven Performance!

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Give your engine the rock-solid valve control of shaft mount rocker arms.

Take your rocker arms to the top level with more horsepower and reliability. Made for the most demanding racing applications, Scorpion Racing Products Endurance Series Shaft Mount Rocker Arms smoothly transfer camshaft motion to the valve by properly positioning the rocker over the valve. The rockers are mounted on a stand rather than on separate studs so valve train stability, stiffness and geometry are improved considerably. And a stable valve train means much better performance and more horsepower potential. Don’t settle for less… WIN with the best!

100% CNC machined in the USA and feature:

  • Fully radiused rocker bodies made from aerospace-grade 7000 Series aluminum
  • All steel rocker components made from ASTM-certified bearing quality steel
  • 4140 heat-treated steel stands
  • .562-inch diameter centerless ground shafts
  • .625-inch adjuster engagement
  • Each lightened assembled rocker weighs only 120 grams
  • Exclusive 100% Lifetime Warranty!

Applications: Chevrolet, Chrysler, Ford, Oldsmobile & Pontiac

Miami Springs Memories

From it's first event in July of 1954 to it's last race on August 13, 2005 Hialeah Speedway provided countless memories for local race fans. Do you have any memories of this hotbed of South Florida racing?
From it’s first event in July of 1954 to it’s last race on August 13, 2005 Hialeah Speedway provided countless memories for local race fans. Do you have any memories of this hotbed of South Florida racing?

Scorpion Endurance Series Rocker Arms Available at Summit Racing

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Scorpion Endurance Series rocker arms offer you power that perseveres. With less weight and a lower profile these American-made Endurance rocker arms are built with the stamina to get the job done in winning style. Scorpion specifically designed these rocker arms for endurance racing engines with better fitment under most stock valve covers with no interference and they can easily handle a .950 in. lift and 950 lbs. of open spring pressure. Plus, they’re approximately 28 grams lighter than their Race rockers! Endurance rocker arms are micro-polished to endure over a long period and are anodized for additional protection, as well as providing great aesthetics. Choose your ratio and gain the stamina to sting your competition with Scorpion Endurance Series rocker arms.

Additional features include:

* Aerospace-grade 7000 series aluminum
* Full body design
* Precision ground need bearings
* Centerless-ground fulcrum
* Ground pin and roller
* Burr-free trunnion through hole
* Large machined seat
* Solid steel pedestals
* Black oxide coated steel parts

FLASHBACK FRIDAY: 6 Years Ago Today

25541_1236035387176_2478963_nInvestors from as far away as Europe were treated like royalty when they came to tour the new Scorpion Performance facility in Ocala, Florida.

Owner and CEO, Rob Stopanio greets investors as they arrive 6 years ago today.