The first step on the road to success with any LS, even a boosted one, is always a cam swap!
When it comes right down to it, all dyno testing is fun, some tests are just more fun than others. Case in point, any test that involves what we call the A-Team, meaning a motor from the wrecking yard, a cam swap and boost! Now toss in the chemical composition known as E85 and you have the makings of a real performance party. It is important to note that, like all successful parties, this one was well planned.
Unlike most build ups, we didn’t have a specific power goal in mind, but what we did have was a list of parts we wanted to try on our test motor. The parts were naturally related, as the recently introduced LS supercharger kit from TorqStorm we planned to run all but required the use of a dedicated Comp cam. It goes without saying that any LS build up will get a cam swap, but not just any cam would do for our supercharged LR4. Rather than put a naturally aspirated cam in and hope for the best, we planned ahead and requested a dedicated blower cam from Comp Cams designed for a centrifugal supercharger application. As we would see, the cam offered plenty of extra power, even in naturally aspirated trim.
The use of the supercharger not only helped dictate the cam profile for our build, but the fuel as well. As much as we like running on pump gas, the limitations drive us nuts. Who likes having to pull timing and reduce the power output when all that wonderful boost is just begging for more? Not wanting to limit the motor by running on 91-octane pump gas (Cali Premium), we decided that E85 was the only way to go.
Much less expensive than dedicated race fuel, E85 is the go-to choice for a lot of boosted builds on a budget. In the interest of full disclosure, we ran E85 from Rocket Brand, but the power and boost level would certainly be attainable on pump E85. Since we were running E85, that meant the combination required sufficient injector flow. Again, planning is important and one factor of the build will certainly influence another. Another example of this would be the blower cam requiring a suitable valve spring upgrade. The high-lift (and rpm) cam naturally required something other than the stock truck valve springs. Thus, we had the domino effect from our choice of a supercharger.
Now that we had a plan, it was time to put it into action, starting with our motor. Fresh from the wrecking yard, this was not our best outing in terms of power plants. We should have looked it over more closely, or at least pulled a valve cover. The color and amount of sludge in the oil was beyond belief, but hey, it ran! Up on the dyno with long-tube headers and an electric water pump, the high-mileage 4.8L produced peak numbers of 329 hp and 315 lb-ft of torque. After the dyno test, we tore into the 4.8L with reckless abandon, and swapped in the new Comp cam.
As mentioned previously, the 54-477-11 grind was designed for a blower application and featured a .614/.624 lift split, a 227.243-degree duration split and 114-degree lsa. The cam swap included the installation of the 26918 valve springs. Equipped with the blower cam, the injected 4.8L produced 429 hp at 6,700 rpm and 346 lb-ft of torque at 5,400 rpm. Despite being designed for a blower, the Comp cam improved the power output of the 4.8L by a solid 100 hp. Heck, even the torque was up from the stock cam. As excited as we were about the extra power from the cam, we couldn’t wait to put it to even better use with the supercharger.
The blower was the reason for the cam choice, which in turn required the spring upgrade. The blower also required the switch over to E85 fuel, as all the previous testing had been run on 91-octane pump gas. Installation of the TorqStorm supercharger required only a couple of mounting brackets and a new crank hub. The hub was secured using a dowel pin and retaining bolt after drilling the face of the crankshaft.
Once we had the crank pulley and spring-loaded belt tensioner in place, it was time for some boost. After configuring a discharge tube to the throttle body, the TorqStorm centrifugal supercharger pumped out a peak of 14.9 psi. Run at this boost level on E85 with our Comp blower cam, the 4.8L pumped out an impressive 694 hp at 6,700 rpm and 571 lb-ft of torque at 5,800 rpm. There was more in the combination with more engine speed, but we felt that was plenty of power for our little 4.8L. The A Team of cam, chemicals and boost had literally transformed our LR4 into one serious player. Oh how we love it when a plan comes together.