When Chevrolet announced that the fifth-generation Camaro would come with two different V-8 engine depending on what transmission the customer ordered, many enthusiasts were a bit confused. The LS3, rated at 426hp, would ship with six-speed manual Camaros, and sport a traditional LS configuration and a fair amount of horsepower. Automatically shifted V-8 Camaros were to be equipped with an L99 LS engine that took the LS3 configuration and added Active Fuel Management (AFM) and Variable Valve Timing (VVT), but also reduced power to "only" 400hp. AFM is the General's way of switching the L99 between running on all eight cylinders—as we are all used to—and running on only four cylinders to increase gas mileage, which, for most of us, is nothing more than an inconvenience. VVT on the other hand, well, that phases the camshaft in real time to create impressive torque down low, paired with increased horsepower up top.
Now, if you're thinking that the addition of new technology would help power and make the L99 a better engine, you're somewhat correct. But, sometimes the peak numbers just don't tell the entire story. You see, VVT is actually a great advance in pushrod V-8 technology, as it allows tuners and engine builders to manipulate the camshaft phasing throughout the powerband to create a nice torque curve. No more "flat on the bottom, big power up top" stuff here; it's "killer torque down low and big power up top" with the right setup. And you can see this in the power ratings, where the lower compression, smaller camshaft equipped L99 is rated within 10 lb-ft of torque compared to the LS3, which shows how well cam phasing works.
Of course, where the factory may have fallen a bit short in power and performance, the aftermarket has made great strides. The genius team of engineers at Comp Cams have been working hard since day one to create a line of VVT specific camshafts that work with the existing system to maximize horsepower and torque output, while keeping the L99 engine trouble free and sophisticated.
Comp Cams offers several high performance camshafts for the L99, with everything from a mild duration upgrade to a more aggressive bumpstick for racers, and we naturally ordered the largest one they offered. With 218/222 degrees of duration, 0.566/0.578 inches of lift, and a 114-degree lobe separation, the Comp Cams 189-403-13 camshaft selected for this build is "aggressive" by VVT standards, but really quite mild for a typical street driven LS3-style build. Additionally, we had Comp send us a set of standard LS hydraulic roller lifters (PN 850-16), hardened 7.400-inch pushrods (PN 7955-16), dual valvesprings (PN 26925TS-KIT), and a Comp Cams phaser limiter kit (PN 5460) to tame the VVT phaser movement. Additionally, we chose to upgrade the factory rocker arms with Comp's rocker arm trunion kit (PN 13702-KIT), which is something everyone should consider when installing a new camshaft.
With parts in hand, we teamed up with the crew at Vengeance Racing in Cumming, Georgia, to follow along with the installation on an already mildly modified fifth-gen Camaro. The Vengeance team is no stranger to the high-performance LS world, and was able to complete the entire installation in no time, without any headaches. At home, this would be a difficult—but not impossible—installation, as the heads do have to be removed in order to delete the AFM system. However, when we hit the dyno, the results spoke for themselves…
Vengeance Racing's L99 equipped Camaro came into the shop running a cold-air intake system, long-tube headers, and a cat-back exhaust. Baseline dyno runs recorded 365.37 rwhp and 382.77 lb-ft of torque to the rear tires, which showed the engine was in tip-top shape and running well prior to our installation.
Comp Cams has worked hard to develop Variable Valve Timing (VVT) compatible camshafts for the L99 LS engine, and their complete kit includes a VVT specific camshaft, a set of 16 hydraulic roller lifters, high-lift compatible valve springs, a set of 7.400-inch hardened pushrods, and a cam phaser limiter kit.
With four camshaft profiles to choose from in the existing VVT lineup, we naturally picked the largest of the bunch, part number 189-403-13. At .050-inches, the 275PIIHR144 grind runs 222/236 degrees of duration, .566/.578 inches of lift, and a 114-degree lobe separation angle. Somewhat aggressive by VVT standards, this camshaft was cut to promote modest power gains without giving up drivability on the street.
Vengeance Racing technician Joseph Johnson (Joe) wasted no time digging into the fifth-gen's engine bay. With the coolant drained and the factory water hoses removed, Joe pulled the radiator out of the way. Of note, the factory transmission cooler lines must also be disconnected prior to removal, which is a simple pull and hold job.
With the radiator removed, Joe had plenty of room to work on the front of the L99 engine. The next step was to remove the factory water pump. With the belt removed, Joe loosened the pump from the block and pulled it out of the way. Don't forget about the two heater hoses attached to the side.
Next, it was time for the balancer to go. Using an LS-specific pulley removal tool and an air-powered impact, Joe pulled the balancer and carefully set it aside. Like most of the front engine components, the balancer will be reused, so make sure to keep it in good shape if you're doing this at home.
The timing cover attaches to the front of the L99 with eight perimeter bolts and two lower oil pan bolts. Those lower two bolts, which go into the timing cover vertically, can be difficult to access without a slim ratcheting wrench, but you can get to them with some patience.
Jumping up top, it was time to remove the spark plug wires, coil packs, and the crossover fuel line to gain access to the valve covers. With the covers removed, Joe pulled the factory rocker arms off of the cylinder heads, then pulled the stock pushrods out of the engine.
Next, the intake manifold was removed, along with the fuel rails and injectors. There is a large vacuum hose behind the intake manifold; make sure you disconnect it from your brake booster before pulling up, or you'll find yourself stuck on the way out.
Unlike a "typical" LS3 cam swap, the VVT camshaft system requires builders to remove the factory Active Fuel Management (AFM) lifters. These lifters just can't handle the lift of an aggressive camshaft, and must be swapped for a set of Comp Cams supplied hydraulic roller units. This means the cylinder heads have to come off.
Pulling the L99 cylinder heads is an easy job for the crew at Vengeance Racing, but it can certainly be a little intimidating for a DIY garage job. With the long-tube headers removed, Joe unbolted the cylinder heads and pulled them off of the engine.
Next, the oil pump was removed, which requires unbolting the oil pump pickup tube from the pump prior to removal. The pickup tube bolt is easily the most frustrating bolt to access on the LS engine and, if you're not careful, can easily end up in the oil pan. Take your time, work slowly, and don't drop the bolt!
A single bolt holds the VVT timing gear to the camshaft. Once removed, the timing gear can be pulled off the end of the camshaft by hand. Note that the factory timing chain tensioner must be relieved prior to removal, which can be done by holding the tensioner to the side with a small pin.
Finally, it was time to pull the camshaft out of the L99. If anything, this is the point of no return, but if you've made it this far, you're half way there. Joe takes care to remove the factory camshaft slowly to ensure he doesn't scratch or gouge any cam bearings on the way out. Then the new Comp unit is coated in Royal Purple and slid in place.
Remember that Comp Cams phaser limiter kit? Well, it was time to modify the factory VVT timing set to limit the camshaft phaser's motion. In stock form, the VVT phaser is capable of advancing or retarding the camshaft by 52 degrees. The Comp Cams kit limits that swing to 22-degrees, "providing the necessary valve clearance for more aggressive hydraulic roller camshafts with tighter lobe separations, all while still reaping the benefits of GM VVT technology."
Comp provides excellent instructions in the phaser kit, which makes installing the limiter a simple task. Using a vice, Joe clamped down the timing gear and utilized the provided tool to rotate and lock the phaser in position. Then, he swung the rear cover out of the way, installed the limiter, and reassembled the timing set.
Installing the modified VVT timing gear is as easy as dropping it back in place and bolting it down. Joe lined the camshaft up dot-to-dot and tightened everything down to spec. At this point, you can put the oil pump back in place, tighten down the pickup tube, and reinstall the front timing cover.
Removal of the factory AFM lifters requires replacing the stock L99 valley cover with an LS3 unit, which is as easy as bolting the new LS3 cover in place. The L99 cover (top) controls oil flow to the stock AFM lifters and, with those lifters removed, can cause a low oil pressure situation. The LS3 unit covers the factory oil galley and keeps everything working harmoniously.
The new 0.566/0.578-inch lift camshaft would wreak havoc on the factory valvesprings. Comp recommends switching to a quality single or dual spring with this camshaft. Vengeance Racing installed a set of Comp Cams' dual springs, which include new tool steel retainers, 7-degree valve locks, new seats, and seals. Installation is as simple as pulling the stock springs and dropping the new units in place.
Finally, it was time to slide the new 7.400-inch, one-piece hardened pushrods into the cylinder heads, then get to work on reassembling the top half of the engine. The factory rocker arms bolt back in place, then the valve covers, coils, plugs, wires, headers, intake manifold, and remaining components can go back where they belong. After that, it was off to the dyno …
With Mike Carnahan of Vengeance PCM behind the laptop, a new tune file was loaded into the VCM and our test Camaro was run through the paces. The new Comp Cams' VVT camshaft kit laid down 404.39 rwhp and 385.27 lb-ft of torque through the automatic transmission, a gain of 39.02 rwhp and 2.6 lb-ft of torque, even with the VVT phaser limited to 22 degrees.
Looking closer at the dyno graph, it's easy to see just how much more useable power the Comp Cams bumpstick delivers. From 4,500 to almost 6,500, power is up across the board, carrying far past the factory camshaft. On the street or track, this would be noticeable, to say the least. And, best of all, we got to keep the VVT functionality!