Camshaft gear variances can...
Camshaft gear variances can lead to spark scatter at high-rpm levels-exactly where you race. To solve this problem, Comp can have the camshaft gears cut separately on high-tolerance CNC machinery and then press it onto the cam.
ValveSprings "The valvesprings are a pretty interesting area for development because the beehive-style springs are really catching on," Brown says. "The first beehive spring we made was for a NASCAR restrictor-plate application, and now they are everywhere. We are also using an ovate wire spring where the wire itself is an oval shape instead of the conventional round cross section. The extra surface area of the wire gives it extra strength without adding excess weight.
"The beehive shape also has a couple of advantages. First, because each coil is a different diameter than the one above and below it, they all have different natural frequencies. They are more forgiving when it comes to harmonics than a conventionally shaped spring. Also, the smaller diameter at the top means a smaller retainer is used, and that can save around five grams per spring.
"The only problem with a beehive spring is you cannot run an inner spring, which limits the maximum spring pressure. That shouldn't be a problem for too long. In fact, it won't be long before we have a single ovate beehive spring that you can run on a Saturday night, 0.700-lift roller cam."
Distributor Gears "Traditionally, the gears on the cam to turn the distributor are cut with a machine called a hob," Brown states. "But to do a really good job, the hob needs a wide range of motion. That's not possible with the distributor gears on a cam because they are sitting right next to a journal, which restricts the hob's access. We started using a second machine called a shaper after the hob, and that improved the quality of the ignition gears, but it still wasn't enough for the NASCAR guys. Ignition timing is critical to them because of the amount of time their engines spend at high rpm. They wanted to reduce the spark scatter to practically nothing.
Comp's engineers say that...
Comp's engineers say that using lifters that restrict the movement of the pushrod seat can increase the maximum rpm range in a racing engine with a hydraulic cam.
"Spark scatter is simply a variance in the timing of the spark. Let's say you are running an engine at 9,000 rpm and you put a timing light on it. When you look at the timing with a typical camshaft and distributor setup, it's going to be jumping all over with about five degrees of variance. Normally, it's the slack, or the backlash, between the gears on the cam and the distributor shaft that allows this variance in timing. One solution has been to press the distributor gear into the cam gear so that there is no slack, but if the gear is the slightest bit out of concentricity, it will cause the whole thing to bind up and kill the distributor gear.
"So we finally came up with the idea for a Chevrolet cam to take the rear journal and distributor gear off the cam and just leave a spud there. Then we can CNC-machine the cam gear to very tight tolerances and press it and the journal back on. Now everything is located and the spark scatter is reduced to two degrees at most. Plus, you regain the ability to index the distributor gear in and out from the cam so that you can nail the backlash perfectly."
So, What is Nitriding, Exactly?Of all the innovations Brown pointed out, he said nitrided camshafts will likely be one of the most helpful advancements for Saturday night racers. For more information on nitriding and what it means to you, we spent a little time with Billy Godbold, one of Comp Cams' camshaft designers.
"Nitriding is best for racers using flat tappet camshafts because it is only beneficial for reducing sliding friction," he explains. "The biggest problem for a flat tappet cam is lobe failure. There is only so much lobe lift you can run before the lobe gets too pointy and it wears the nose out. There is only so much spring you can run before it wears the nose out. And there is the velocity limit when you are running flat tappet lifters. All of those limits have to do with wear.