Here at Super Chevy, we love dyno testing, but that doesn’t change the fact that some components offer greater differences in power enhancement than others. Things like headers, carbs, and roller rockers can certainly add power on the right application, but the gains from these are usually minor compared to what we call the big three. When it comes to normally aspirated performance, the big three include the heads, cam, and (for our needs) intake manifold.
The LS1 family responds very well to both ported heads and cam upgrades, but what about intake swaps? The factory GM intakes (LS1, LS6, and truck) all offer plenty of performance—surprising for a factory intake. The question before us was if an LS1-style engine already possessed adequate head flow and cam timing, would it be receptive to one of the Edelbrock Pro-Flo XT intake upgrades? There’s only one way to find out, so we decided to dyno test it.
Truth be told, the success of an intake swap is as much about the combination as it is about the intake design, but know that a bad intake design will hurt the right combination even more than a good one will help the wrong combination. The two must be matched for maximum performance. To achieve this symbiotic relationship, we set out to design a suitable test mill for the Edelbrock Pro-Flo XT intake. What we had was a stock 5.7l LS1 crate motor, but what we needed was something that would tax the flow and power potential of the Pro-Flo XT intake.
To up the ante on our test engine, we replaced the two remaining big-three components, namely the heads and cam, prior to testing the intake. The LS1 crate engine was equipped with a healthy Crane hydraulic roller street cam that offered 0.600 lift, a 232/240 duration split, and 110-degree lobe-separation angle. The cam was combined with Crane hydraulic roller lifters and double roller timing chain. Working with the cam swap was a set of RHS cathedral-port heads and a 6.0L truck intake. Though no longer offered, the CNC-ported RHS heads offered enough flow to support north of 600 hp, or more than enough for our modified LS1.
The idea for this test was to run the modified LS1 with the stock intake and then again with the Edelbrock Pro-Flow XT manifold to compare the differences. Edelbrock claimed gains of as much as 30 hp, so we were pretty excited going in. The engine was configured on the engine dyno with American Racing long-tube headers and a Holley HP management system. The 6.0L truck intake was equipped with an Accufab throttle body, 42-pound injectors, then tuned to perfection using the Holley management system.
Once tuned, the modified LS1 produced 512 hp at 6,700 rpm and 453 lb-ft of torque at 4,900 rpm. Torque production exceeded 425 lb-ft from 4,100 rpm to 6,200 rpm. Hoping for the additional 30 hp, we installed the Edelbrock intake. After installation of the Pro-Flo XT intake, the numbers jumped to 551 hp at 6,800 rpm and 451 lb-ft of torque at 5,800 rpm, a gain of not 30 hp, but an amazing 39 hp! As expected, there was a trade-off in power lower in the rev range, but even averaging the power production from 3,000-7,000 rpm, the Edelbrock came out on top.
01. Our dyno mule started out as a simple 5.7L LS1 crate motor from Chevrolet Performance (nee GM Performance Parts). The one that started the revolution, the LS1 is still an excellent motivational source for any Chevy-powered machine.
02. In stock trim, the LS1 was a good Chevy, but not a super Chevy, so we made a few upgrades before testing the Edelbrock intake. First to go was the stock stick, replaced by a healthy Crane cam that offered 0.600 lift, a 232/240 duration split, and 110-degree LSA.
03. The stock 241 LS1 heads were replaced with a set of RHS cathedral-port heads (no longer available). The CNC-ported RHS heads featured 225cc intake ports and flowed enough to support more than 600 hp. There are other excellent cathedral-port heads now available, but we had these, so we used them.
04. On hand for tuning was a Holley HP EFI system. The only way to optimize safe power production was to dial in the air/fuel and timing with each intake.
05. The test motor was run with a set of 1¾-inch headers from American Racing Headers feeding a pair of 3-inch dyno mufflers.
06. To establish a baseline, the modified LS1 was first run with a stock truck intake. Equipped as such, the 5.7L produced 512 hp at 6,700 rpm and 453 lb-ft of torque at 4,900 rpm.
07. After testing the stock truck intake, we were excited about the installation of the new Flo-Flo XT intake. According to Edelbrock, the Pro-Flow XT manifold was designed to operate over a broad powerband from 1,500-7,000 rpm.
08. We made the mistake of not ordering the optional fuel rails, so we had to improvise using a set of FAST billet rails. Since our injector harness was designed for early Jetronic injectors, we installed these USCAR-Jetronic adapters.
9. The Edelbrock intake featured a dedicated mount and vacuum source for the factory MAP sensor.
10. Edelbrock offers a dedicated throttle body for the Pro-Flo intake, but we opted for this 90mm unit from Holley. Two different intakes are available from Edelbrock, one that required an Edelbrock throttle body and one that accepted the stock LS2-style throttle body. Edelbrock also offered an adapter to covert the Edelbrock-only flange to standard GM.
11. After swapping over the O-ring intake gaskets, we installed the Edelbrock intake onto the awaiting LS1. The intake was impressive and much better looking than any of the factory intakes.
12. Equipped with the Edelbrock intake, the modified LS1 produced 551 hp at 6,800 rpm and 451 lb-ft of torque at 5,800 rpm, a gain of 39 hp.
13. Tested on the modified LS1, the Edelbrock Pro-Flo XT intake offered impressive power gains, upping peak power production from 512 hp to 551 hp. The peak torque was down by an insignificant 2 lb-ft, but note that peak torque shifted by nearly 1,000 rpm, from 4,900 rpm to 5,800 rpm. This is a clear indication that the Edelbrock intake favored power production in the top end of the rev range on this 5.7L LS1. In fact, the stock intake offered more power up to 5,600 rpm, but this crossover point would drop lower in the rev range on a 6.0L, 6.2L, or stroker version.