As the money and competition in the Nextel Cup Series have skyrocketed in recent years, the image of a Nextel Cup engine builder has changed. The old mechanic who learned about engines working in his daddy's garage is still there, but working right alongside him is a mechanical engineer who spent his youth studying the laws of thermodynamics. It's a different world from the old days (Maurice Petty told us once that he used to scrounge junkyards looking for parts for Richard Petty's cars), but that's OK because that's what is needed to continue the pace of innovation.
Much of that innovation, however, doesn't come from inside the engine shop but from outside sources. Many of the advancements in race engine technology actually come from the parts manufacturers working closely with the race teams to give them what they need. That's the good news for a Saturday night racer. After all, the last thing a Nextel Cup team wants to do is pass along its discoveries to anyone else, but an innovative parts manufacturer can take what it learns racing on the Nextel Cup level and use that knowledge to help everyone go a little faster.
Advancements in camshaft grinding technologies have improved the surface finish on the lob
To find out more about how high-end racing affects the little guy, we called up the folks at Compe- tition Cams and asked a few personal questions. Comp Cams is a perfect example of this phenomenon because the company produces a wide range of engine parts and is a big player in everything from Nextel Cup, to drag racing, to Saturday night stock cars, all the way to go-karts. Interestingly, there's a lot more going on than we originally thought.
Camshaft Technology "When it comes to the camshafts, the demands of the Nextel Cup and Indy Car teams that we work with required us to go to great lengths to meet their specs," says Chris Brown, Comp's vice president of operations. "But once we figured out how to meet their requirements, it was relatively easy to continue those improvements to our other cams.
"The number one thing that we've done is have our camshaft design team work with every type of engine out there. We've got three cam designers, and instead of having them specialize in certain types of engines, they all work on everything from Nextel Cup, to Top Fuel drag racing, to street cars, to oval track stock car racing. They even do the cams for go-kart racing. That's really paid off for us because of the depth of knowledge that those guys have acquired. They understand what's happening inside an engine a lot more than somebody who only has access to one style of engine. So now when they encounter a problem for a Saturday night race engine, they can draw on their experiences with how drag racers or Nextel Cup racers solved a similar problem.
Super-precise measurement equipment such as this Adcole machine allows cam grinding techni
"The upper-level guys are always raising the specs that they need for their products. That's why we acquired an Adcole machine that checks cam tolerances. But what happened was our guys on the manual cam grinders started using it to tune up their machines and methods for all their stuff. In the past couple of years, they have gone from having a window on their duration specs from 0.5 to 0.75 of a degree down to 0.2 to 0.25. Without having to tell them, their own pride in their workmanship has brought them down that path.
"We've also learned a lot about surface finishes, what works best on a roller (cam) and what works best on a flat tappet. We've taken what we've learned from micropolishing and used it to test different types of grinding stones so that the stone itself leaves a different finish on the cam lobes. That's helped us improve the lobe surface finish for guys that don't want to or cannot pay for micropolishing. All that stuff is directly related to some of the high-end cams we have done for NASCAR teams because they often put a spec on the surface finish.
Beehive springs were originally created for restrictor-plate racing, but the design is so
"Something that's pretty interesting is one of the biggest advancements for the racer running a flat tappet cam didn't come from the NASCAR guys, but from working with an Indy Car team. When we first started working with Toyota's Indy Car program a few years ago, they said the cams had to be nitrided. And we said, 'What's nitriding?'
"Nitriding improves the cam's surface finish, and as it turns out, it's not just good for Indy Car racing-it's also helpful in just about any flat tappet application. We're doing it on all our overhead cams, and it's made a big difference in the cams for the 2300cc Ford motors. Those cams for the four-cylinder motors we used to call boomerang cams because you could count on three out of four coming back. So much on those heads has to be just right or the cam will fail. It isn't the cam's fault, but that's what usually got the blame. Anyway, to make a long story short, we started nitriding the 2300 cams and went from a 70 percent failure rate to a 2 percent failure rate in two years. The difference is just incredible, and it can be just as helpful in the V-8 stuff, too."
Lifters "Over the years we had two types of solid roller lifters-let's call them better and best," Brown continues. "The NASCAR Busch and Truck teams used the 'best' lifters and the Saturday night racers used the 'better' lifters. But the advantages of the best lifters have bled down until there's really not much difference between the two. There's no one big thing that you can point to. It's really just different things we learned and applied to other lifters. These are things like changing the size of the needle bearings in the roller to reduce the load on them, drilling oil holes in the body that inject pressurized oil directly into the bearing assembly, and making the axles of tool steel rather than mild steel. It's just a lot of little things that add up to make the lifter a more durable part with a longer life.
Advancements, including holes that feed pressurized oil to the needle bearings and tool st
"The same thing has happened with the hydraulic roller lifters. A lot of the road racers and drag racers have to use them, and what we've learned there can be really helpful to the Street Stock-type racer that is required to use a stock-type hydraulic lifter. We've learned that by controlling the pushrod seat location in those things, we can get a lot better valve control. We've gone from a tappet that maxed out at 6,000 rpm just because things got so out of control, to stuff we now are running at 7,200 rpm. We restrict the amount of movement the pushrod seat has inside the lifter. What that does is prevent it from depressing too far and getting enough hydraulic pressure behind it that it would expand the location of the pushrod seat, which would hold the valve open a little longer."
Pushrods "Pushrods are no longer simply pencil-sized metal rods," asserts Brown. "Now they are available in a variety of diameters and shapes with different wall thicknesses. That's because we've learned that pushrods are important for controlling harmonics as well as simply providing a connection between the lifter and the rocker arm. All that stuff is directly related from extensive spintron testing. For example, the LS1 engine from the factory has a terrible problem with bending the pushrods if you over-rev it. Well, just by going from the factory pushrods to a one-piece pushrod with an 0.080 wall thickness, we've eliminated those issues and gained about 500-700 (rpm) on the redline. The same thing is going on in race engines where you can add a little weight to the pushrods and still gain a lot because you are getting rid of the bending and limiting the harmonics. As little as five years ago, racers were running 51/416-inch-diameter, 0.080 wall pushrods, and now they are using 71/416-inch-diameter pushrods. It looks like a Lincoln log in there, but it works."
Camshaft gear variances can lead to spark scatter at high-rpm levels-exactly where you rac
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 using lifters that restrict the movement of the pushrod seat can
"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.
"Wear is even a problem in the limited lift classes. In that situation, you are trying to open the valve as quickly as possible, hold it near max lift for as long as possible, and then close the valve at the last minute. What you wind up with is a cam lobe with corners on both sides of the cam lobe, and it's those corners that can be damaged under harsh conditions.
"So, what we really are trying to do is keep those from wearing. There are two solutions that can decrease wear-increase the cam's hardness and increase its lubricity-and nitriding the cam does both things.
"The type of nitriding we use is called a plasma nitride. The other method is salt bath nitriding, but that produces only a very thin case, sometimes less than 0.001 inch. Plasma nitriding can produce thick case depths, around 0.01 inch, which is ten times the capability of a salt bath.
"What you are doing is putting the camshaft in a big vacuum vessel. You take most of the air out and pump in nitrogen. Then you put the camshaft and the walls of the container to different potential, like across a battery. The nitrogen cooks up to itself and forms needles. Those nitrogen needles are rapidly accelerated and then crashed into the surface of the camshaft. It's a lot like shot-peening, except instead of shot you are bombarding the surface of the cam with nitrogen, which imbeds itself into the material's atomic structure.
"Nitrogen behaves a lot like carbon. It gives the cam a very hard, slick surface. It is almost like putting little ball bearings along the surface of the cam lobes. This means the camshaft is going to last much longer. Engine builders can go with more aggressive lobes they couldn't use before, and you are going to decrease wear tremendously. It's not twice as long or three times as long for the typical cam versus a nitrided cam; it's 10 or 12 times more life span. Getting a cam nitrided will cost around $150, but given the benefits, I think it's a very cost-efficient upgrade."