Today, it's all about the total package. You wouldn't order your eggs without salt, pepper, and assorted Tabasco sauces, right? Nor can you be a successful football quarterback without the right playbook and talented linemen to protect you. The same goes for your high-tech LS engine, and deriving the best power, reliability, and drivability requires a well-designed combination of parts.
To achieve the best bang for the buck, you need to select parts that work together as a team. And when you start with a sophisticated piece of engineering such as your Corvette's LS engine, unless you have a performance plan, you could be in for big trouble.
Recognizing this, Comp Cams and the Comp Performance Group Companies set out to build a series of power-improving packages that fit both the performance and budgetary requirements of today's LS-engine (LS1, LS2, and LS6) owners. For those of us who can never have enough horsepower or torque, this five-stage program makes it possible to add a little or a lot of both.
As noted, the Comp LS upgrades fall into five stages, each featuring a group of power-matched components. These part combinations were selected through countless hours of dyno testing, tuning, and retesting at Comp's headquarters in Memphis. The results are documented through the SuperFlow dyno charts supplied with this story.
For this installment, we decided to include the first four upgrade stages, holding the more involved Racing Head Service (RHS) cylinder-head swap for next time. Note that each stage builds on the last. In other words, you can't skip over stages to increase horsepower, as each new stage requires the installation of the previous level.
All of our tests were performed on a factory-fresh LS1 engine that generated 375 hp and 370 lb-ft of torque in Comp's baseline dyno tests.
There are plenty of urban legends about the power of handheld programmers. The fact is a properly engineered unit can do great things to improve the power, fuel efficiency, and drivability of your vehicle. The FAST-FLASH Power Programmer is arguably one of the easiest-to-use programmers on the market. You simply plug it into the diagnostic port under your Corvette's dashboard, read the text in the viewing screen, and answer a series of questions by pressing the buttons on the face of the programmer. Like most handheld programmers, the FAST-FLASH unit "remembers" your ECM's original settings, so you can revert to this baseline point whenever you desire.
To optimize the programmer's potential, Comp engineers decided to address what is perhaps the LS-series engines' most serious inherent deficiency. Simply stated, the factory-supplied LS1 pushrods are weak-so weak that in early Spintron testing, both camshaft lift and duration were compromised by pushrod flex. The fix: a set of 0.080-inch-wall, 51/416-inch-diameter, 7.400-inch-long Hi-Tech pushrods. These pushrods fit in the stock location and don't require any cylinder-head modifications.
The final change was to add a set of ZEX performance spark plugs. These plugs feature a heat range designed to deliver increased performance, long life, and excellent fouling resistance in a street-based LS engine.
With our new parts installed and the FAST-FLASH Power Programmer hooked up, a number of dyno pulls were completed. By programming the FAST-FLASH to Power Tune Setting No. 2 and leaning out the mixture slightly with a "Minus 5" fuel/air configuration, we unlocked 11 additional horsepower and 12 more lb-ft of torque.
As in Stage I, our Stage II upgrades focused on building power while also strengthening the engine for future modifications. The biggest change at the Stage II level was the installation of Comp beehive valvesprings (PN 26918). In Spintron testing, beehive springs have been shown to deliver a host of performance and durability improvements, including reduced valvetrain weight and increased valvetrain stability. These single-coil, ovate-wire springs also feature reduced spring-seat pressure for better valve control.
Ideal for dual-purpose applications, the beehive springs retain durability for on-street driving but can also handle more rpm and aggressive cam profiles (up to approximately 0.600-inch lift) for racing conditions. Comp has determined that thanks to their smaller-diameter top coils, these springs are also quicker to react to compression by the rocker system.
The beehive springs use much smaller retainers than their conventional counterparts. Additionally, the retainers included with the Stage II package are made of 4140 chrome-moly steel, making them significantly lighter than the factory units. In essence, the beehive springs and their smaller retainers can reduce valvetrain weight by twice as much as a set of super-expensive titanium valves (approximately 928 grams, or more than two pounds!).
To take full advantage of the beehive springs, we installed a set of Comp Pro Magnum rocker arms with a higher-than-stock ratio. These ultra-durable steel rockers are made from 8650 chrome-moly and carry a lifetime warranty (on the rocker body.) They feature a 1.75:1 ratio-a slight change from the factory 1.70:1-ratio units. In addition, we bolstered the valvetrain with new Comp rocker studs and pushrod guide plates, both critical upgrades for this engine application.
It's important to note that all of these valvetrain-component changes are compatible with the factory-supplied valve covers, so no one needs to know what lurks inside your engine but you. The results of all our modifications thus far? A total of 18 more horsepower and 16 more lb-ft of torque than stock.
Time for some big power gains? You bet. And what better way than through a camshaft change? As you might have guessed, the selection of exactly the right cam involved a number of different dyno tests. The key was to select a grind that delivered excellent power and torque but also maintained decent idle characteristics and the vacuum required for accessories.
At this point, Comp recommends installing its new Type-"R" hydraulic roller lifters, which extend the engine's upper-rpm range by reducing bleed-down. (They do require a 0.002-0.004-inch preload, mandating an adjustable valvetrain). After the lifters were installed, a number of camshafts were tested to determine the most significant power improvement. It was clear the factory cam specs (200-/210-degree duration, 0.497-inch lift, 118-degree lobe separation) would not suffice for what we had planned.
Comp's Xtreme Energy (XE) camshafts are designed for street/strip applications where both improved throttle response and top-end horsepower are the targets. Both of these characteristics are achieved by using aggressive lobe profiles that require upgraded valvetrain components (hence, the valvetrain enhancements included in Stage II of our upgrade program).
The XE-R hydraulic camshaft was installed in the normal fashion, along with a bottle of Comp Break-in Lube (PN 159), which was poured into the engine. Comp recommends Shell Rotella oil for the initial break-in procedure, as it includes many of the break-in ingredients not found in today's more common motor oils.
The XE-R camshaft that netted the best performance (PN 54-444-11) featured 224-/230-degree duration, 0.581-/0.588-inch lift (measured at the valve with 1.70:1 factory rockers), and 114-degree lobe centers. Using the 1.75:1 Pro Magnum rockers and all the equipment from the earlier stages, we generated 56 additional horsepower and 36 more lb-ft of torque.
With most of our modifications to this point having addressed internal engine upgrades, it was time to focus on air intake. The FAST LSX intake manifold (available in both 78mm and 90mm versions) uses an innovative polymer material and is designed to increase air flow without the weight penalty exacted by some other aftermarket intakes. The manifold is compatible with boosted and nitrous engine upgrades, as well as with the upsized FAST 90mm throttle body.
Because we had installed a higher-lift, higher-duration camshaft, we knew it was a good idea to increase the fuel delivery as well. The FAST Fuel Rail Set bolts up to the LSX manifold and greatly increases the fuel available to avert potential starvation.
The FAST LSX installed easily and felt considerably more substantial than the factory intake. The 90mm throttle body looked massive compared with the stock 78mm unit (more like 75mm, according to our measurements) and would, in fact, require a larger-inlet air-intake system when installed in a car.
It's important to note that the FAST throttle bodies are only available with a cable throttle system, so folks using "drive-by-wire" systems would be best served by installing a 90mm factory LS2 throttle body. Interestingly, Comp engineers noted that the 78mm intake system produced slightly better torque numbers than the 90mm unit though it was unable to hit the same horsepower level.
With our new parts torqued in place and no apparent leaks, it was time to run the dyno again. As we suspected, the horsepower and torque figures once again increased. Compared with stock figures, the new combination netted 64 additional horsepower and 40 extra lb-ft of torque.
Clearly, we had witnessed dramatic improvements in our LS engine's power and torque. Best of all, these were daily-driver-compatible changes that could easily be replicated by any C5 or C6 owner with access to tools and a modicum of mechanical skill. In our next installment, we'll bolt on new cylinder heads designed to complement the package we have created so far. Stay tuned. It's gonna be fun.