Camshaft And Valvetrain Technology Insight - On The Lobe's Edge

A Look At The Latest Camshaft And Valvetrain Technology Straight From Its Creators

John Nelson Feb 1, 2009 0 Comment(s)
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The Crower brain trust also pays attention to the rest of the valvetrain, carrying an extensive line of valvesprings engineered to work with the company's camshafts.

Crower Cams
For most of this endeavor, it seemed like everyone wanted to talk about LSx parts, and you can certainly get your Gen III and IV needs taken care of at Crower. In fact, the larger cam core sizes these engine use mirror what Crower is doing with many of the cams it does for aftermarket-block small- and big-blocks. Now, it's not that you can't get a street-oriented bumpstick from Crower-you'll find plenty of appropriate pieces in the company's catalog. On the other hand, Crower concentrates its efforts on ultra-high-performance pieces and race components. So when we asked Dave Crower about the kind of things he's been seeing lately, he immediately mentioned base circles. "We're seeing lots of bigger cam bearings so we can make the base circles, and therefore the cam lobes, bigger," he reported. A standard base circle is 1.868 inches, a big-block uses a 1.948 base circle, and the LS engines use a 2.168 base circle. "These larger base circles are primarily for roller tappets," he told us. "When you go with a bigger base circle, the lifter doesn't come as much out of the bore, so it's better supported and there's horsepower to be had." Surprisingly to us, these gains aren't just because a bigger base circle can run more-aggressive cam lobes. "There's the shear factor of the lobe pushing against the lifter," Crower continued. In other words, the lobe actually tries to shear the lifter off. "When the journal goes bigger, it's a big advantage powerwise." For instance, if you go to a 50mm cam core, you pick up 300 rpm of control and a degree or a degree-and-a-half of duration throughout. "The trend is to get the base circle as big as possible," Crower said, and he agreed with us that the increasing popularity of aftermarket blocks has facilitated this.

Crower has also taken a hard look at its valvetrain components in the search for more power. "Every gram you get off the valve equals 25 extra rpm. So if your valve weighs 10 grams less, that's 250 extra rpm you can spin the engine. It's like a whole-point rocker increase." You also need a good picture of the valvetrain, Crower said. If you make the spring and retainer lighter, at the same rpm you've got 20 percent less load over cam, which means 20 percent less pressure over nose. And the less weight there, the less wear on the bearings. "It's not uncommon to see NASCAR guys run under 1.300-inch od springs with 65-gram intake valves to 9,000 rpm."

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Crower is always at work creating new parts for the hardcore contingent. One of its latest is a line of tool steel cams that don't require hard facing. They are subjected to heat treating and nitriding, but the real advantage for racers is the 0.62- to 0.63-inch wear surface. How hard are they? Crower says 65 Rockwell, compared to a typical 40-48 Rockwell.

Crower also pays close attention to spring rates. Using the Harvey Crane idea of camshaft intensity, the company pays close attention to the difference between advertised duration and 0.050 duration when recommending valvesprings. For instance, according to Crower, a cam with a wide spread between these figures is a smooth camshaft and doesn't require high spring pressure. As the difference drops, these faster, more intense cams need extra spring.

Crower has also been doing a brisk business in tool steel cams that don't require hard facing. They are heat-treated and nitrided and have a very thick 0.062- to 0.063-inch wear material. They're also really hard-65 Rockwell compared to a typical 40-48 Rockwell, says Crower. It's definitely a hard-core race 'stick, and Crower figures they sell 500-800 a year, as well as 500 sets of the hardened, polished lifters that go with them.

Other trends Crower sees? Besides needle bearing cams, which the company does a couple hundred of a year, he noted lots of firing-order-change cams. "We do a lot of 4-7 swaps in roller cams," he said. "We also do a lot of LS1 firing-order cams: 4-7/2-3. The swap helps distribution in the carb and harmonics in the block." That sounds like something CHP might have to test out sometime.

Crower is also selling more stainless rocker bodies-especially shaft setups and split-ratio arrangements like 1.6/1.7 and 1.7/1.8. Many of these are fitted with Crower's needle bearing rocker tips. "They're very advantageous for reducing valve guide wear, and you'll be surprised at how much easier the engine spins over." In fact, said Crower, more than half of the shaft-mount systems the company sells have needle bearings.

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One of Crower's biggest stocks in trade are its stainless rocker bodies, many of which come fitted with the company's needle bearing rocker tips. According to Crower, the engine spins more freely and valve guide wear is reduced. More than half of the shaft-mount setups Crower sells are fitted with this option.

If there's anything else that Crower wanted to get across, it was to encourage buyers to call and get a recommendation. "We do more custom cams than shelf grinds," he told us. When it comes to street applications, Crower continually stays with moderate cams so heavy springs aren't required. "If you put high-flow heads on a street engine, you may lose low-end power," Crower reminded us. "And you may need a smaller cam. The biggest thing is to supply us with head flow numbers."

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Crower also does extensive business in larger cam cores, such as the 50mm LS1-size core. Bigger journals have multiple advantages. They're easier on lifters and allow for better valve control at higher rpm, and this while still running more aggressive lobes, leading to power gains. The popularity of aftermarket blocks has allowed for more frequent use of larger core sizes.


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