Isky Racing Camshaft Design Secrets - CHP Insider
Nolan Jamora Of Isky Racing Reveals The Secrets Of Camshaft Design And Selection
From the November, 2009 issue of Chevy High Performance
By Stephen Kim
Photography by Courtesy of the manufacturers
Statements like this are sure to generate buzz, but Isky Racing could just be the most prolific innovator in the history of hot rodding. In the 1950s, when aftermarket camshafts didn't exist, Ed Iskenderian learned how to grind them himself. Dry lake racers went nuts, and the art of engine building was forever changed. No wonder Iskenderian earned the nickname "The Camfather." As advances in cam design pushed valvetrain components to the limit, he invented necessities that we take for granted today, such as antipump lifters, performance valvesprings, rev kits, and antiwalk buttons. On any given test-and-tune night at any given track, most racers probably have all of those components in their engines. Furthermore, Iskenderian was the first to use computers in cam design, served as the first president of SEMA, and introduced the concept of corporate sponsorship to professional drag racing when he teamed up with Don Garlits.
Over the decades, Isky Racing Cams has remained at the forefront of camshaft and valvetrain technology, and its innovative spirit hasn't waned one bit. We couldn't resist the urge to talk shop with this legendary manufacturer, and as we expected, the chatter turned very technical very quickly. During our time with Nolan Jamora, head of R&D at Isky, we discussed everything from simulating races on Spintrons to lofting lifters for power. Much of the information floating out there regarding camshaft design is bogus, but some of it isn't, so to know the difference you must read on.
Although Ed Iskenderian's countless innovations have kept his company at the leading edge of camshaft and valvetrain technology for decades, his beginnings were very humble. While still attending high school in Los Angeles in the 1930s, Ed's pet project was a Model T roadster, and by working on it day and night he learned the fundamentals of mechanics that would help him later on in life. After graduating, Ed obtained mechanical experience working as an apprentice tool and die maker. During this time, he worked on making his Model T faster with the help of his good friend Ed Winfield.
After serving in the Air Transport Command during WWII, flying supplies to the islands of the Pacific, Ed wasted no time getting back to his hot rod and getting ready for the dry lake meets. When rebuilding his V-8, he wanted to obtain a special camshaft. However, there were very few racing camshaft manufacturers on the West Coast. Their production schedules were taxed, which resulted in slow delivery. During the five-month waiting period for his special camshaft, Ed decided to enter the cam grinding business and bought a used conventional cylindrical grinder. Drawing on his tool making and mechanical experience, Ed converted it to a universal cam-grinding machine. This machine produced camshafts with a noticeable improvement in performance over the conventional racing camshafts. Ed's cams were the first to produce 1 hp per cube on gasoline in postwar Dodge Hemis, and 1.3 hp per cube in 283 Chevy V-8s.
Back in the 1950s you couldn't just go out and buy a cam core. With the lack of cores and cam grinding equipment at the time, the challenge of creating lobe profiles in addition to manufacturing cams that improved performance was tremendous. "In the early days, we did a lot of regrinds where we took the stock core and put a new profile on it. We made the ramps longer to create more lift and duration," Jamora explains. This practice is still common today for some of the harder to come by cores in many import motors.
"As for the lobe profiles themselves, early on it was all about trying something different to see what worked," Jamora continues. "Ed saw that racers could benefit from the advancement of higher technology in racing, so he created the first hard-face overlay camshafts in the industry and became the first to employ computers in camshaft design. With the computer, Ed created the most advanced cam profiles of the late 1950s and early '60s, like the famous 5-Cycle and Polydyne Profile 505 Magnum, along with the very first hydraulic racing camshafts in the industry."
Over the years, the equipment available to cam manufacturers has changed dramatically, evolving from simple cylindrical grinders to Spintrons and Notron grinders. Naturally, these advancements mean the camshafts of today are far superior to the ones available decades ago. "Ed has always believed in acquiring new technology to push forward. We believe better and more accurate cam and master grinding machines in addition to better information gathering and testing technology helps us push development forward at faster and faster rates," says Jamora. "When we combine our Spintron, computer simulators, and dyno testing with our Accu-Cam precision profile measurements, accuracy standards, and feedback from engine builders, we know we have accurate data we can depend on. I think everything we do is based on past design limitations and the attempt to push each part to the limit or next level. Each new breakthrough is an evolution, and the more data you have, the clearer the path becomes to your goal. The better the testing and manufacturing, the better the product."
Camshaft design is all about valvetrain inertia as a whole. You must design the entire valvetrain to work as a single system. The goal is to have the valve motion be the same as the designed cam motion. The problem is that the weight of all the parts, the elasticity of the components, and the effects of the springs all work against the cam motion at high rpm. During the initial opening of the valve, the lifters, pushrods, rockers, and valvesprings are compressed into action. The lobe design has to be quick yet smooth so you don't transfer any bad harmonics into the system, which will cause spring surge and destroy them. As you run up the ramp to the nose, the valve is opening farther, the parts are compressing more, and the dynamic loads are getting higher. All this stresses the system. Over the nose at max lift, the valvetrain is fully compressed and fighting to rebound against the force imparted on it. At high rpm, the inertia of the whole system going over the nose fights the return spring force, and the lifter wants to hang in the air instead of following the cam design. Hopefully the mass of the valvetrain and high spring pressures allow the lifter to follow the cam all the way down the ramp. If not, the lifter will bounce, which kills the valve seat and sends harmonics that destroy the springs as well as the needles in the roller lifters. This reduces the volumetric efficiency of the engine, as the valve doesn't seat properly and robs horsepower.
Isky was the first to utilize computer design in the development of performance camshafts. Not only did this help optimize performance, it significantly streamlined manufacturing. "The time it took our customers to receive a custom cam went from several weeks to one week by simply implementing a scientific calculator. Then it went from a week to days as the process evolved, but you still had to hand finish the master cam, which took days in the 1970s and '80s," Jamora recollects. New software design programs soon came out that cut the design time down to hours and enabled grinding a master using NC punch cards in a day or so. "Now you can design a new ramp in a few hours from scratch, send it to the CNC grinder, and grind the cam or master in minutes. It saves a tremendous amount of time and helps push R&D forward."
Jamora continues, "Sometimes an engine builder will call me and say 'I want to try this and that.' I tell him, 'That's not going to work, but I'll cut it for you if you want.' I'll get a call a week later from the guy saying, 'You were right, but I had to know for myself, so let's try it your way this time.' Experimenting like that just wasn't possible decades ago, and it's all thanks to computer technology. These days you have different cams for each different track."
From the very early days at Isky, Ed learned that in order to get to the next level in performance, you need to have matched valvetrain components. Many of the parts we take for granted simply didn't exist during hot rodding's infancy, so Ed had to invent them. Every time a racer would push for bigger lifts and durations, other parts would break. The lifters couldn't take the fast opening rates, the springs couldn't survive the violent closing rates, and this would destroy the valvetrain. In the early days, you couldn't just go buy new rockers and springs. You had to design them yourself. Consequently, Isky is credited with manufacturing the first antipump lifters, computer-designed lobes, performance valvesprings, rev kits, and antiwalk buttons.
It's a never-ending ladder of development where one breakthrough leads to other failures. Then when that failure is solved, you push a little more and the next weak point in the valvetrain presents itself. All of our breakthroughs as a company have come from necessity. If you wanted to be more aggressive with the cam you needed better lifters, stronger pushrods, and stronger springs. In every decade you see new innovations. From the advent of computer design in the early 1950s and '60s, to roller lifters and cams in the '60s, to antipump up lifters and shaft rockers in the '70s and '80s, to new profiles and big journal sizes of the '90s, to the even more complex cam designs and better springs of this decade, valvetrain technology is always on the move.
The Spintron is a machine that's known as a spin fixture. It was designed and built by Bob Fox of Trend Performance. It has a 50hp electric motor that spins a test engine up to 12,000 rpm. We can program the machine to perform simulation runs at various tracks. For example, we have a test that simulates running at Daytona in a NASCAR Sprint Cup car, which includes the warm-up, practice, qualifying, and race with yellow flags and pit stops. We also have a test simulating Pro Stock and Pro Mod runs including the burnout. This enables us to collect data and see if our new profiles and parts perform up to task.
We measure data in the block with a laser to track actual valve motion as well as high-speed cameras to see what the parts actually go through at high rpm. The forces are very violent. If you think about it, at 9,000 rpm the valve opens and closes about 75 times per second. Snap your finger, and in that amount of time the valve has banged open and shut 75 times. The dynamic pressures involved are unbelievable.
The Spintron and the information we gather from it pushed us to design our Gold Strip Tool Room series of springs and our EZ-Roll bushing lifters. This, in turn, helped us push closer to the edge of what is possible in cam design.
Thanks to modern cam design software, lobe profiles are more advanced than ever. Cam manufacturers now have the flexibility to integrate three to four different cam event sections onto a single opening ramp to create the perfect lobe profile. "It is important that the velocity, acceleration, and jerk imparted on the valvetrain is smooth and continuous, and being able to design each section optimally improves design greatly," says Jamora. "For example, our profiles that have dwell at max velocity allow us to design for the most area under the curve without exceeding the maximum velocity of the tappet. This dwell at maximum velocity allows us to use a larger radius of curvature at the nose of the profile. By being able to quicken the valve opening rate using high-ratio rockers, we can get a lot more into the ramps, which allows us to get more power. This was not possible in the past because the valvetrain could not take the shock, but with better modern-day springs we can design cams to their true potential."
In the walk of cams, there's surface hardness and torsional hardness, and both are critical to maximum performance and longevity. Without adequate surface hardness, the lifters can dig into the cam lobes, so a quality core goes a long way in enhancing durability.
"Torsional hardness is also very important," says Jamora. "Today we are using better materials and bigger journals so that we can get the stiffness we need to cut down on any harmonics coming from the camshaft. We want to eliminate any flex in all areas of the valvetrain."
Dual vs. Single Pattern
After all these years, there is still a lot of debate regarding single- and dual-pattern camshafts. According to Jamora, it all depends on the application. For naturally aspirated hydraulic flat-tappet motors, Jamora recommends a single-pattern cam for maximum power. However, Isky's research has found that dual-pattern cams with a roughly 6-degree spread can improve fuel economy and low- and midrange torque.
"These cams have minimal valve overlap to maintain smooth idling with stock and aftermarket carbs and intakes," says Jamora. "They are great for towing applications and with heads that have restrictive exhaust ports, as the longer exhaust duration allows better breathing to promote torque production. On late-models like LS1s that already have hydraulic roller cams, we opt for as much as 12 degrees of split. In these setups a dual pattern really works the best, and as you go up in rpm range, the more spread you want to use. I think the most important thing is to talk to someone who really knows cams. Each application will be a little different, and getting the right cam recommendation is a must."
Lift, Duration, & LSA
Designing a camshaft is all about juggling the duration, lift, and lobe-separation angle to optimize the shape of the powerband for a given application. If you have a camshaft with the same lift and duration, you can change where the power and torque come on in the same rpm band. For example, in a Pro Stock or Pro Mod motor, we set most of them on a 116- to 118-degree LSA, whereas we used to run them at 108-112 degrees. The tighter LSA created too much torque down low, which resulted in tire shake. Using a wider LSA moved the power higher up in the rpm band, eliminating tire shake and making the power more useable. Likewise, in certain oval track classes we run into rules that limit maximum lift. In situations where we're limited to 0.410-inch lift, we run upwards of 248-250 degrees duration at 0.050 and are still able to make power at 7,000 rpm. As you can see, lift and duration go hand in hand, in terms of making power while the lobe-separation angle affects where in that powerband you'll make peak power and torque.
Needleless Lifter Bearings
Extensive testing confirmed that needle-roller motion in the roller bearing is subject to harmonic wavelike action, in which the needles bunch up then spread apart. This is due to the deflection of the outer bearing race under extremely heavy valvespring loads and tremendous dynamic forces. The poor ratio of load distribution over the surface area of the bearing compounds the problem. This is why even a set of high-end $2,000 roller lifters will fail from time to time.
To solve this problem, we came up with our EZ Roll bearing, which achieves a load rating 350 percent greater by eliminating the needles themselves and replacing them with a roller bushing. Our ultralow-friction raceway material rolls so easily under heavy loads (450 lb/in seat and 1,400 lb/in open) and high rpm (over 10,000) that top engine builders report they seem to run forever. Because of the dramatic improvements from our EZ Roll Redzone lifters, in many cases you eliminate the need to overbore the lifter holes, so you can avoid the cost and the increased weight associated with oversize lifters.
We now have many new cam grinds that take advantage of this newfound valvetrain stability. These lifters don't bounce or flex, which keeps harmonics out of the valvetrain and improves durability. If you do lose a spring or a rocker and the lifter ends up bouncing around, it will never shatter the roller bearing and spread needles through the engine. They work great in everything from street engines to Pro Mod setups.
Most valvesprings fail because of resonant vibrations at high rpm. They key is to reduce the harmonics in the valvetrain as effectively as possible. Most springs will go through two harmonic problem areas in the rpm range. Says Jamora, "It's like leaving the line in a Pro Stock car, getting into tire shake 20 feet out, and just driving though it. That tire shake affects the whole car and breaks parts. Spring harmonics are very similar, and you either have to design the problem areas to occur in an rpm range that will not affect the engine performance-at very high or very low rpm-or you have to come up with better materials and manufacturing. Using the Spintron, computer simulators, and on-track testing, we are able to do both. We use a revolutionary new alloy steel that is very clean, and we also have many proprietary finishing processes that allow the spring to last at high rpm a long time. Our newest Tool Room series of springs, the Super Rads, not only use our latest alloy, but are also nitride heat-treated."