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)
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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.

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Computer Design
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."

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Valvetrain Breakthroughs
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.


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