MSD Atomic LS7 Intake: 684 hp @ 6,900 rpm
Largest Gain: 52 hp @ 6,000 rpm
The MSD Atomic intake started well and then became excellent as the tach zoomed past 4,500 rpm. Even down low, the Atomic offered improved power, but the intake really came alive after passing 4,500 rpm. Compared to the stock LS7 intake, the MSD increased the peak output by 42 hp but offered as much as 52 hp elsewhere in the curve.
Stock LS7 vs MSD Atomic for LS7, Modified LS7 (Torque)
Stock LS7 Intake: 554 ft-lbs @ 5,400 rpm
MSD Atomic LS7 Intake: 586 ft-lbs @ 5,100 rpm
Largest Gain: 40 ft-lbs @ 5,000 rpm
As much as I love an extra 42 hp, I love extra torque through the entire rev range even more. As this chapter illustrates, top-end gains are often accompanied by losses in low-speed (and mid-range) torque. This was not the case on the Atomic intake test. The MSD AirForce intake improved torque production through the tested rev range and improved torque output by as much as 54 ft-lbs.
Test 4: Stock LS3 vs Speedmaster IR on a Modified LS3
More than just a change in runner length, this test involved a comparison between a conventional long-runner factory intake and an individual-runner (IR) intake from Speedmaster. The IR intake differed from the factory not only in the length of the runners (although they were different), but also in the lack of a common plenum. Each of the runners on the stock LS3 intake was connected to a common plenum fed by a single throttle body. By comparison, the Speedmaster intake featured no common plenum and eight individual throttle bodies, which measured 50 mm.
Some might be quick to point out that the IR system offered better airflow from the increased surface area of the eight throttle blades. However, the change in runner length, combined with the lack of a common plenum and, therefore, the absence of Helmholtz resonance are what really produced the power differences. (You know this because of the lack of vacuum present in the stock intake at wide-open throttle, or WOT.)
Let’s face it: Nothing is sexier than an individual-runner (IR) intake on an LS engine. This unit from Speedmaster offered impressive power gains to go along with its good looks.
This test was a comparison between the stock LS3 intake and the Speedmaster IR manifold. The test engine was a crate LS3 upgraded with a Comp (PN 281LRRHR13) cam (.617/.624 lift split, 231/247 duration split, 113 LSA) and CNC-ported, TFS Gen X 255 heads. The LS3 crate engine from Gandrud Chevrolet was run with Kooks headers, a Holley HP management system, and Meziere electric water pump. Run on the dyno with the stock LS3 intake, the modified LS3 produced 575 hp at 6,500 rpm and 517 ft-lbs of torque at 5,500 rpm. As always, the long-runner, factory intake offered an impressive torque curve.
After installation of the Speedmaster IR intake, the peak power numbers jumped to 605 hp at 6,800 rpm and 533 ft-lbs of torque at 5,000 rpm. I liked the fact that both peak horsepower and torque were up, but also that the peak torque occurred lower in the rev range with the IR intake. With the exception of a small area near 4,500 rpm, the IR intake equaled or bettered the factory intake through the entire rev range.
The Speedmaster IR intake offered anodized fuel rails, full-radiused air horns, and individual ports to combine the MAP sensor readings.
Stock LS3 vs Speedmaster IR on a Modified LS3 (Horsepower)
Stock LS3 Intake: 575 hp @ 6,500 rpm
Speedmaster IR LS3 Intake: 605 hp @ 6,800 rpm
Largest Gain: 36 hp @ 6,800 rpm
With the exception of a slight dip in power near 4,500 rpm, the Speedmaster IR induction system improved the power output through the RPM range. There was a bump in power near 5,000 rpm and then a serious jump past 5,500 rpm. This intake would show even greater power gains on a larger or wilder application.
Stock LS3 vs Speedmaster IR on a Modified LS3 (Torque)
Stock LS3 Intake: 517 ft-lbs @ 5,500 rpm
Speedmaster IR LS3 Intake: 533 ft-lbs @ 5,000 rpm
Largest Gain: 22 ft-lbs @ 5,000 rpm
The torque curve shows the sign wave in power created by the IR intake from Speedmaster. The new induction system lost out in torque from 4,200 to 4,700 rpm, but bettered the stock LS3 intake everywhere else. A resonance wave at 5,000 rpm really bolstered torque production.
Test 5: Stock LS3 vs Speedmaster Fabricated Intake on a Mild LS3
A number of sources offer these fabricated intakes, but Speedmaster supplied this particular test piece for the LS3 application. Once again I was looking at a substantial change in runner length, to say nothing of plenum volume and throttle opening. Where the stock LS3 intake was designed to accept a 90-mm throttle body, the Speedmaster fabricated intake featured a 102-mm opening.
Various sources offer fabricated intake in different configurations, both with and without radiused air horns for the runners. If you plan to run one, make sure you select the one with air horns because the smooth air entry is worth 10 to 12 hp over the non-radiused version (at this power level).
The overall look of the intake combined with the cost make it a desirable commodity, but look over the dyno results before making your choice, especially for a mild street application. The intake certainly has its place, but like other short-runner intakes, there is a trade-off in low-speed (and mid-range) torque on all but the largest and wildest combos, which includes turbo and blower applications.
This test was run on an engine that clearly favored the long-runner, factory intake. The Gandrud LS3 crate engine was simply augmented with a mild 224 Crane cam (.624/.590 lift, 224/232 duration, 113 LSA), a set of long-tube 1¾-inch Quick Time Performance (QTP) headers with extensions, and mufflers. The test mule also featured a Holley 90-mm throttle body (stock intake), stock LS3 injectors (raised fuel pressure), and Holley HP management system. Run with the stock LS3 intake, the mild LS3 produced 538 hp at 6,300 rpm, and 504 ft-lbs of torque at 4,800 rpm.
After installation of the fabricated intake, the peak power jumped to 556 hp at (a higher) 6,800 rpm, but peak torque dropped to 485 ft-lbs of torque at 5,200 rpm. The stock intake offered improved power up to 6,050 rpm, where the fabricated began to pull away. This intake works much better on high-RPM or larger (and wilder) applications than on this mild LS3.