Pushrods

"Pushrods are no longer simply pencil-sized metal rods,"asserts Brown. "Now they are available in a variety of diameters andshapes with different wall thicknesses. That's because we've learnedthat pushrods are important for controlling harmonics as well as simplyproviding a connection between the lifter and the rocker arm. All thatstuff is directly related from extensive spintron testing. For example,the LS1 engine from the factory has a terrible problem with bending thepushrods if you over-rev it. Well, just by going from the factorypushrods to a one-piece pushrod with an 0.080 wall thickness, we'veeliminated 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 littleweight to the pushrods and still gain a lot because you are getting ridof the bending and limiting the harmonics. As little as five years ago,racers were running 5/16-inch-diameter, 0.080 wall pushrods, and nowthey are using 7/16-inch-diameter pushrods. It looks like a Lincoln login there, but it works."

ValveSprings

"The valvesprings are a pretty interesting area fordevelopment because the beehive-style springs are really catching on,"Brown says. "The first beehive spring we made was for a NASCARrestrictor-plate application, and now they are everywhere. We are alsousing an ovate wire spring where the wire itself is an oval shapeinstead of the conventional round cross section. The extra surface areaof the wire gives it extra strength without adding excess weight.

"Thebeehive shape also has a couple of advantages. First, because each coilis a different diameter than the one above and below it, they all havedifferent natural frequencies. They are more forgiving when it comes toharmonics than a conventionally shaped spring. Also, the smallerdiameter at the top means a smaller retainer is used, and that can savearound five grams per spring.

"The only problem with a beehive spring isyou cannot run an inner spring, which limits the maximum springpressure. That shouldn't be a problem for too long. In fact, it won't belong before we have a single ovate beehive spring that you can run on aSaturday night, 0.700-lift roller cam."

Distributor Gears

"Traditionally, the gears on the cam to turn thedistributor are cut with a machine called a hob," Brown states. "But todo a really good job, the hob needs a wide range of motion. That's notpossible with the distributor gears on a cam because they are sittingright next to a journal, which restricts the hob's access. We startedusing a second machine called a shaper after the hob, and that improvedthe quality of the ignition gears, but it still wasn't enough for theNASCAR guys. Ignition timing is critical to them because of the amountof time their engines spend at high rpm. They wanted to reduce the sparkscatter to practically nothing.

"Spark scatter is simply a variance inthe timing of the spark. Let's say you are running an engine at 9,000rpm and you put a timing light on it. When you look at the timing with atypical camshaft and distributor setup, it's going to be jumping allover with about five degrees of variance. Normally, it's the slack, orthe backlash, between the gears on the cam and the distributor shaftthat allows this variance in timing. One solution has been to press thedistributor gear into the cam gear so that there is no slack, but if thegear is the slightest bit out of concentricity, it will cause the wholething to bind up and kill the distributor gear.

"So we finally came upwith the idea for a Chevrolet cam to take the rear journal anddistributor gear off the cam and just leave a spud there. Then we canCNC-machine the cam gear to very tight tolerances and press it and thejournal back on. Now everything is located and the spark scatter isreduced to two degrees at most. Plus, you regain the ability to indexthe distributor gear in and out from the cam so that you can nail thebacklash perfectly."

So, What is Nitriding, Exactly?

Of all the innovations Brown pointed out, he said nitrided camshaftswill likely be one of the most helpful advancements for Saturday nightracers. For more information on nitriding and what it means to you, wespent a little time with Billy Godbold, one of Comp Cams' camshaftdesigners.

"Nitriding is best for racers using flat tappet camshaftsbecause it is only beneficial for reducing sliding friction," heexplains. "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 toopointy and it wears the nose out. There is only so much spring you canrun before it wears the nose out. And there is the velocity limit whenyou are running flat tappet lifters. All of those limits have to do withwear.

"Wear is even a problem in the limited lift classes. In thatsituation, you are trying to open the valve as quickly as possible, holdit near max lift for as long as possible, and then close the valve atthe last minute. What you wind up with is a cam lobe with corners onboth sides of the cam lobe, and it's those corners that can be damagedunder harsh conditions.

"So, what we really are trying to do is keepthose from wearing. There are two solutions that can decreasewear--increase the cam's hardness and increase its lubricity--andnitriding the cam does both things.

"The type of nitriding we use iscalled a plasma nitride. The other method is salt bath nitriding, butthat produces only a very thin case, sometimes less than 0.001 inch.Plasma nitriding can produce thick case depths, around 0.01 inch, whichis ten times the capability of a salt bath.

"What you are doing isputting the camshaft in a big vacuum vessel. You take most of the airout and pump in nitrogen. Then you put the camshaft and the walls of thecontainer to different potential, like across a battery. The nitrogencooks up to itself and forms needles. Those nitrogen needles are rapidlyaccelerated and then crashed into the surface of the camshaft. It's alot like shot-peening, except instead of shot you are bombarding thesurface of the cam with nitrogen, which imbeds itself into thematerial's atomic structure.

"Nitrogen behaves a lot like carbon. Itgives the cam a very hard, slick surface. It is almost like puttinglittle ball bearings along the surface of the cam lobes. This means thecamshaft is going to last much longer. Engine builders can go with moreaggressive lobes they couldn't use before, and you are going to decreasewear tremendously. It's not twice as long or three times as long for thetypical 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, Ithink it's a very cost-efficient upgrade."

SOURCE
COMP Cams