Isky Racing Camshaft Design Secrets - CHP Insider

Nolan Jamora Of Isky Racing Reveals The Secrets Of Camshaft Design And Selection

Stephen Kim Nov 1, 2009 0 Comment(s)

Lobe 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."

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Hardness
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.

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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.

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Valvespring Harmonics
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."

Sources

Isky Racing Cams
Gardena, CA 90248
323-770-0930
www.iskycams.com

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