Tech: Choosing A Better Stick

Rod Short Feb 5, 2013 0 Comment(s)

With today’s Internet dyno jockeys, bench racers and chat room engine experts, separating the facts from fiction on late-model cam swaps can be both intimidating and confusing. That’s why Virginia Speed in Virginia Beach has been busy in recent months sorting out camshafts for LS3 street applications. With the difference in architecture between the first-gen Chevy small-block and the LS series of engines, the thought process behind what made one engine work best may not be the same with the other.

“A lot of people call in looking for the most peak horsepower they can find,” said Shawn Miller, the shop manager and engine builder at Virginia Speed. “To be realistic, peak horsepower is really just a tool for bragging rights and sales. Before everyone had chassis dynos, the only way people could really compare was by taking your car out to the local drag strip to compare time slips. Nowadays, people can run their cars on a chassis dyno to compare peak horsepower figures, but that doesn’t tell you if the car has the mid-range power you need for it to drive well or feel good.

“An engine is very rarely at peak horsepower,” Shawn continued. “If you’re going down the street or strip, 90-percent of the time you’re not at peak horsepower because when you are, it’s time to shift. The ‘seat-of-your-pants’ feeling that everybody likes is all found in the mid-range combination of power and torque, not in the peak horsepower.”

Thorough testing of new cam profiles is an important process in validating what looks good on paper—and on the computer screen. It also eliminates a lot of guesswork, time and money for the end user. For many looking into making a cam swap, the most common mistake in choosing the right grind lies in being too aggressive. Cam profiles that produce the biggest numbers are most often intended for high rpm ranges, and don’t do as well in street driven engine applications because of the rumpity-rump idle quality—at the sacrifice of driveability and torque. Part of that is due to an increase in duration or decrease in lobe separation angle because the valve overlap makes fueling inconsistent at idle. Drastic changes in the camshaft profile can also require wholesale changes throughout the rest of the valvetrain as well, such as new valvesprings, rocker arms, and pushrods.Link text....

Sucp 1302 05 O Tech Choosing A Better Stick Ls Engine 4/9

“When it comes to camshaft changes, these engines are very particular,” Shawn said of the LS family. “The cylinder head on the LS3 has a very big intake, so you have to be aware of potential valve-to-piston clearance issues. With a flat top piston, you have to be very careful about how big of a camshaft you put in it, duration-wise. You also have to be careful because they have a very big intake runner in the cylinder head, so if you try to over-cam the thing, it’s going to drive like a piece of junk on the street. It took a lot of trial and error over time to get these things to drive nice and still make good power.”

Crane Cams partnered with Virginia Speed to develop three different street grinds, ranging from mild to slightly wild to give the LS3 owner a roller cam that will provide great mid-range power and torque for fun driving on the street while still providing good manners.

Compatibility with the existing architecture of the LS3 engine, as well as the stock Camshaft and Crankshaft Position sensors, was of utmost importance. With the triggering devices and sensors changing with the year and engine version, Crane’s addressed the compatibility issues that came with those changes by using a three-bolt design camshaft with a different timing chain set.

Sucp 1302 06 O Tech Choosing A Better Stick Testing And 5/9

“The smallest cam was designed for someone who wants more power with virtually no cam lope,” Shawn said when asked about the differences between the three cams tested here. “It offers more power everywhere, but you don’t lose much driveability and you can still run a stock converter if you have an automatic car. The second cam is something that offers more horsepower, but you would need a mild stall converter in an automatic. It has more of a lope, but is still very driveable. The third cam is what I would consider for guys who are willing to deal with lope and low rpm, parking lot buck and jerk.

“All of them work well in making mid-range power with no valve-to-piston problems.” Shawn concluded. “It’s a great street cam that offers a good balance of power and driveability. People love them.” j

Part Number Grind Number Adv. Duration Intake / Exhaust Duration at .050” Lift Intake / Exhaust Degree Lobe Separation Valve Lift with 1.70 Intake / Exhaust
1449371 HR-216/347-2S-13 4A 272 / 289 216 / 232 113 0.590 / 0.624
Designed for LS3–6.2L applications, this cam will work well for a daily driver with increased horsepower from 2,000 to 6,000 rpm, and providing a broad flat torque band with increased torque between 4,500 to 5,000 rpm. Good fuel economy. Works with stock 10.5:1 compression ratio. Computer upgrades are advised when using this camshaft. Will work with stock converter.
1449381 HR-220/347-2S-13 4A 276 / 293 220 / 236 113 0.590 / 0.624
Intended for LS3-6.2L applications, this cam will work well for a daily driver with increased horsepower and higher rpm from 2,200 to 6,400 rpm while maintaining the increase street-able broad torque band. Fair fuel economy. Works with stock 10.5:1 compression ratio. Computer upgrades are advised when using this camshaft along with headers and aftermarket exhaust system. For cars with automatic transmissions, a 2,800 to 3,200 stall converter is suggested.
1449391 HR-226/367-2S1-14 283 / 297 226 / 240 114 0.624 / 0624
Ground specifically for LS3-6.0L applications, this cam works well for an above average weekend driver with street/strip in mind. Increases in both horsepower & torque at 2,600 to 6,500-plus rpm with a choppy idle. Increased compression ratio up to 11.5:1 and computer upgrades are advised when using this camshaft, along with a lower gear ratio, headers and aftermarket exhaust system. For cars with automatic transmissions, a 3,200 to 3,600 stall converter is suggested.

Sources
Crane Cams
386/310-4875
cranecams.com

Virginia Speed
757/468-5101
www.virginiaspeed.com

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