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Rocker Arm Tech With Comp Cams and T&D Machine - Off Your Rocker

Jake Amatisto Sep 19, 2012
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The rocker arm is possibly the third most abused part in your engine. The connecting rods take the cake for the most abuse, followed closely by the piston assembly, but we like to think the rocker arms get the bronze for beatings when you’re goosing the throttle in your V-8 of choice.

When it comes to building a performance engine, rockers can do more than simply transfer the motion of the pushrod; rocker arms can change rpm limits, rpm acceleration, and they can even alter your camshaft’s overall behavior. Although simple in theory, rockers are actually far from simple in the high-performance and racing world. In a stock engine, we imagine the rockers live a boring life; basically just transitioning the movement of the pushrod, easily pushing down the low-pressure single coil valvesprings until the cows come home. But as your desire for horsepower increases, the durability and construction of the rockers you choose has to improve as well if you want the most from your engine combo.

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Choosing the right rocker isn’t the only thing to keep in mind, you also have to install them correctly, and sometimes, if you don’t know what to look for, it can be tricky. As we change camshaft profiles, valvespring heights, and mill and deck our engine blocks and heads, those all factor into getting the rockers to fit properly and valvetrain fitment is crucial for a long-lasting engine combination.

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T&D Machine is one company that prides themselves on creating some of the most radical rocker arm systems, including rockers for Pro Mod drag racers and NASCAR “Cup” engines. When you’re limited to specific cam profiles, engine builders often use custom rocker ratios to achieve their desired lift without physically changing the cam specs. However, high-ratio rockers increase the velocity of the valve, which can decrease the life of valveguides and they can also complicate getting the geometry correct.

According to COMP Cams, there are three ways to improve your engine’s power output through a rocker arm change: Use a higher ratio rocker arm to increase overall cam lift and duration, make the rocker body stiffer so no lift is lost by flex, or lower the weight of the rocker so it can accelerate quicker. Increasing the rocker ratio is a way to trick your camshaft into thinking it’s bigger than it actually is. By manufacturing rocker bodies with various arm lengths, this increases the ratio, thus increasing the final lift and duration at the valve. This is oftentimes what gearheads do if they need more cam but don’t want to pull the engine apart. As valvespring pressures increase, rocker body stiffness plays a huge factor in getting the most from your rockers. For years, the engines in the NASCAR circuit used aluminum rockers, but relatively recently engineers have figured out that the amount of flex coming from pushing on super-stout valvesprings was reducing the overall lift of their camshaft, which prompted all the NASCAR teams to switch to lightweight, yet low deflection rockers so they could get every fraction of cam lift from their profile. Reduced rocker body mass is another way companies have improved rocker arm performance over the years. The more rpm your engine experiences, the more valvetrain mass becomes important. For a low-rpm engine, rocker weight/mass is not crucial, but on an 8,000- to 10,000-rpm screamer where the rockers move incredibly quickly, every gram counts.

Read on as we explore how to properly install COMP’s Ultra Pro Magnum stud mount roller rockers as well as give some inside info from COMP Cams and T&D Machine’s engineering department.

For good measure

Which Rockers?

From hard-core racing to mild street engines, COMP Cams has been one of the main providers of high-performance rockers for decades. Recently the engineers at COMP have revamped a few of their popular rockers, including their Ultra Gold line and Ultra Pro Magnums, so we contacted Trent Goodwin with some questions about construction and what we can look forward to in the high-performance Chevy world.

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For high-powered and racing combinations, COMP Cams offers some robust shaft rockers that are rumored to handle 10,000 rpm and higher with the right cam/valvespring combo. Instead of each rocker being tied to a stud individually, shaft rockers are all tied together on a steel stand, drastically increasing stability.

CHP: We’ve noticed steel rockers have started to become more popular in recent years, why is that?

COMP Cams: For stud mount rockers, yes, a lot of engine builders use the steel rocker over the aluminum rocker for more strength and being allowed to run a high-spring pressure. If the engine builder is building a high-horsepower application, it may require our Shaft Mount Aluminum Rocker Arms. These rockers are made from 2024 aluminum and use an 8620 hardened steel shaft, which will make this stronger than a steel stud mount rocker.

CHP: We’ve heard that today’s steel roller rockers are actually as light or lighter than some previous aluminum versions, is that true?

COMP Cams: Our new Ultra-Gold ARC Aluminum Roller Rocker offers a new arced design with a channel and contoured top to give the rocker the best strength-to-weight ratio possible. The end result, less weight and a stronger rocker design.

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CHP: Is it true that there’s some maintenance that goes with aluminum rockers?

COMP Cams: You should not use aluminum rockers on applications exceeding 600 pounds of spring pressure. If your application exceeds this, yes we would recommend checking your rockers periodically.

CHP: Are there any new rocker designs coming out for Chevys that you can talk about?

COMP Cams: We are always in the process of designing and coming up with new products and ways to enhance every aspect of the valvetrain of an engine. We are in the process of finalizing our new LS3 Factory Offset rockers. These rockers are made of 850 chrome-moly steel, black oxide exterior finish, oversized trunions and will be offered with a 3/8 stud and 1.8 rocker ratio.

Wild Rockers

In racing applications, getting the rockers to fit can be tricky depending on a few factors. On racing heads where the valves have been moved, angled, or both, custom rockers are usually required. One of the companies out there that handles both high-end rocker assemblies and street/strip setups is T&D machine in Carson City, Nevada. We contacted T&D’s Phil Elliot with some burning inquiries we had on one of the toughest pieces in your engine.

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CHP: Do you think the need for custom offsets has become more common in the last decade? Why or why not? T&D: It certainly is common here. Virtually all engine builders have their own ideas about just what they want in offset or ratio. Because it is based around state-of-the-art CNC technology, T&D has the ability to add special features as needed. CHP: What are some of the more uncommon requests for custom rockers? Any 1.9:1 ratios or 2.3:1? Are those even possible, and what would they be used for?

T&D: T&D attempts to build rocker systems to suit each customer’s engine combo, even when engineering suggests the idea will not fit or work. Those high ratios you mentioned have actually become quite common—even 2.3:1. Yes, they are possible, and work extremely well in rare places such as NASCAR “cup” plate motors where tight camshaft restrictions require “cheating” in other areas.

CHP: What are your thoughts on the steel rockers in high-end racing? Do people ever request custom steel rockers?

T&D: T&D began building steel rocker arms for a very specialized area—race boats that hop in and out of the water, wreaking havoc on valvetrain components. As they evolved, it was discovered that longevity increased threefold. Now, several years into their development, T&D steel rockers have found their way into far more niches than even we imagined, and they account for a fairly high percentage of sales.

CHP: Do you see any advancement for rockers on the horizon?

T&D: I suppose you want us to tell about exotic unobtanium and the secret zero-gram rockers T&D builds for the very elite teams. But truly, T&D excels because it continues to provide the best rockers, using the finest components available, and based on sound engineering principles.


Comp Cams
Memphis, TN 38118
T&D Machine Products
Carson City, NV



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