Cam designers have traditionally been a small lot of dedicated people who have found power sometimes through the applied use of mathematics, but just as often through the sheer redundancy of trial and error. Nowhere else in an engine do so many variables come into play as in the valvetrain, and controlling all those movements is, of course, the camshaft. Properly timing the interplay of events such as when to open and close the valves, ramp speeds, maximum lift, duration, and overlap is critical, but it is made more difficult because a change in any one of these events affects another in some way. That's why custom-ground camshafts have almost always been the territory of big-money racing teams--until now, that is.
Mike Jones is a second- generation racing cam designer. For years, he operated Jones Racing Cams out of California, working mostly with Chevrolet's Indy Car teams. Recently, however, he moved to the East Coast to team with noted head designer Don Losito of Ultra Pro Machining to form Ultra Pro Racing Cams. This new company plans to combine Jones' experience with Ultra Pro's CNC machining expertise to create custom cams for stock car racers that are affordable and tailored specifically to each racer's needs.
The point of this story isn't to push the idea that a custom cam is necessary for every racer. Certainly, it can be helpful for some, but off-the-shelf pieces from the big manufacturers are plenty good, too. It can be helpful to know exactly how a cam is made so that you know what to expect the next time you place an order. Plus, it can be helpful to know what information cam designers need to build the best possible bumpstick for your racer.
Information, Please At first, you might think a custom cam designer would need to know the size and weight of every nut and bolt on your engine, but it isn't true. Jones uses a program he and his father have written (no, it isn't for sale) that helps him determine the best cam profile for any engine combination. Through years of experience, he has determined the main factors he needs to know. They are the engine's bore, stroke, rod length, static compression ratio, the carburetor and its flow, the planned rpm range, and the port flow numbers. Many of the things you might initially think are important are already factored in through the port flow numbers (valve sizes, valve seat angles, type of heads and intake manifold, and so on), or simply have no effect on cam design (weight of the rotating assembly, dry versus wet sump oiling, coated bearings, and so on) and are simply power adders no matter what cam you use.
"The biggest thing for the customer is to have the most accurate flow numbers possible," Jones says. "If the heads are unported, I already know most of the numbers for every head as they come from the manufacturer. If you are racing ported heads, that information gets critical because I don't know who has done the port job and how good it is. Then, I need good flow numbers across the range of valve lifts, not just the maximum flow numbers. Also, if you can flow the heads with the intake manifold attached, that makes the numbers even better."
There is nothing magic in Jones' proprietary software; it simply does the calculations for him. Because it takes specific amounts of air and fuel to make one horsepower, an engine's horsepower is effectively limited by how much air and fuel it can draw into each cylinder. By inputting the necessary information, Jones determines the maximum power potential of your engine combination and at what rpm that occurs, then designs a cam to fit that profile. This is the point where other limitations, such as engine restrictors or limitations of the track or handling, come into play.
Even if you are a budget racer, having a cam ground specifically to yourneeds may not be o
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