Now in its third installment, our crate engine alternative has taken a turn toward the serious. Before we get into that, we should probably bring all the newcomers up to speed. We started things out with a simple trip to the junkyard to procure a more cost effective alternative to the typical crate engine. Thinking we came home with a 5.3L, we actually snagged a smaller 4.8L. The first upgrade saw a carbureted induction system comprised of an Edelbrock Victor Jr. intake and Holley Brawler carb, all controlled by an MSD ignition controller. The result was 331 hp and 316 lb-ft of torque. After adding a Comp cam and new valvesprings, the power output jumped to 441 hp and 354 lb-ft of torque. The ante was then upped with a 100hp shot from a Sniper nitrous kit and the power rose to 554 hp and 501 lb-ft of torque.
As you might imagine, we're happy with the progress so far. We know it's a far cry from the four-digit power levels of all them turbo buildups, but an honest 550 hp in any street car is a serious piece. That being said, the only thing better than two successive modifications adding 100 hp each is obviously three such modifications. While cylinder heads can yield substantial gains, the factory heads worked very well on this little 4.8L. Sure, if we bored and/or stroked the 4.8 out to 5.3, 5.7, or even up to 383 stroker status, CNC-ported heads may well add serious power, but not on a stock-displacement LR4. With 100hp upgrades getting harder and harder to come by, we decided to go off menu and order up one of our favorite meals. Nothing satisfies a power-hungry enthusiast quite like a heaping helping of boost.
Looking strictly at the numbers, we see that the naturally aspirated 4.8L was now producing 441 hp and 354 lb-ft of torque. We also see that the nitrous pushed the power output over the 550hp mark, so our starting point would be 441 hp and our goal would be to exceed the 554 hp offered by the nitrous combo by a solid 100 hp (or more). To that end, we enlisted the aid of a supercharger from the boys at TorqStorm. Yes, I know, turbos are all the rage and, if the Internet is to be believed, can be purchased and run for less than the cost of adding biggie fries to your burger meal, but we decided to go a different route. Besides, TorqStorm recently introduced their LS blower kit, and we had great success with this blower on both early Ford and Chevy engines in previous testing. Besides, the centrifugal supercharger kit was simple to install, and run on our carbureted combo. We liked the fact that the self-contained, billet blower required neither an oil feed nor a drain line. The lack of heat generated by a turbo or two will also make it appealing to many enthusiasts, as will the limited piping and zero fabrication needs.
With the blower in place, we turned our attention to getting the boost from the blower to the engine. Our first step was to replace the Holley 650 Brawler carburetor with a dedicated blow-through carb. The new carb featured adjustable, boost-referenced power valves and was installed in conjunction with a blow-through carb bonnet. TorqStorm supplied a section of tubing that featured their billet blow-off valve (BOV) so we simply positioned the BOV inline between the blower and carb in our custom discharge tube.
After hooking up a few vacuum/boost lines to the dyno and fuel pressure regulator feeding the carburetor, we were nearly ready. Using the MSD ignition we scaled timing back and added a splash of race gas and started tuning. By the time we were done tuning on the carb, the boosted 4.8L threw down peak numbers of 672 hp and 547 lb-ft of torque at a peak boost of 14.8 psi. We were purposely conservative on the timing (a maximum of 22 degrees), but still managed to exceed our goal, besting the nitrous combo by 118 horsepower. All told, the TorqStorm supercharger improved the power output of the carbureted combo by 231 hp (441 hp vs. 672 hp), which is a serious gain in anyone's book. With 547 lb-ft, there was also plenty of torque to get things moving in the right direction.
Photography by Richard Holdener