If you take a look back at Part 1 of our 4.8L series, you will see that the project started out with a quest for a simple, junkyard 5.3L. Unfortunately, our 5.3L turned out to be the smaller 4.8L, a snafu experienced by many LS enthusiasts. Undaunted, we pressed on with the adventure by creating a cheap, crate engine alternative after adding a carbureted induction system to the little LR4. With the introduction of the Edelbrock Victor Jr. intake, Holley 650 Brawler carburetor, and MSD ignition controller, the little 4.8L eventually produced peak numbers of 331 hp at 6,200 rpm and 316 lb-ft of torque at 4,900 rpm. Best of all, the total cost of this ready-to-run, carbureted combination came in right near $1,300, meaning considerably less than you average (and often incomplete) crate engine.
Of course, like most adventures, this buildup was not without its problems, as the displacement, single-plane intake, and even the headers were all wrong for the tiny 4.8L. Rather than swap out these components for ones sized more suitably, we decided to simply increase the power output of the 4.8L to better take advantage of their potential. Enter the cam swap and a quick shot of NOS.
By now, swapping a performance camshaft into your LS is a no-brainer. A cam swap is the number one upgrade for any engine in the LS family, regardless of displacement. It doesn’t matter whether you have a 7.0L LS7 or the tiny 4.8L LR4, nothing wakes up an LS like more aggressive cam timing. The reason for this is that the LS engine family has plenty of head flow and a good induction system, but lacks proper cam timing to take full advantage of these other components.
In the case of the 4.8L, you have basically a 450hp combination saddled with a 350hp camshaft. Having already started down the wrong path for this series with insufficient displacement and excessive intake and header size, we decided to continue on course and chose our cam accordingly. What we are saying here is that we went big, at least big in relation to our tiny little test engine. You see fellow LS enthusiasts, cam timing is relative to displacement. What might be a mild, streetable cam for a 7.0L (or even 6.2L), is actually considerably wilder when applied to the smaller 4.8L. Since we already had a high-rpm intake and oversized headers, why not pick a cam to go with the other components?
With this bigger-is-better philosophy stuck in our heads, we chose one of our favorite LS grinds from the Comp Cams catalog. The cam had performed impressively in just about every LS application we applied it to, regardless of displacement, but we had yet to run it in the 4.8L. No time like the present to rectify that situation. The cam offered a 0.614/0.624-inch lift split, a 227/243-degree duration split, and 113-degree LSA. With the right heads and intake, this cam was capable of producing 550 hp on a 6.2L application. While we would be getting nowhere near that power level with our little 4.8L, it was nice to know we had enough cam to make some serious power if we combined it with the right components.
The Comp cam was teamed with a set of beehive springs since the cam lift and rpm potential were way too much for the stock springs to handle. The spring upgrade was run with the stock retainers, keepers, and pushrods, though hardened pushrods are a good idea when upgrading the springs. After the cam and spring upgrade, the power output of the 4.8L improved to 441 hp and 354 lb-ft of torque. The wilder cam timing pushed peak power all the way up to 7,000 rpm (see dyno graph), and boy did it sound good.
Having improved the power output of the little 4.8L by over 100 hp, you might think we’d be satisfied, but we wanted even more. There is only one thing better than adding 100 hp, and that’s adding 200 hp, right? Looking over the combination, we realized there was no other single component, like the cam, that would add another 100 hp. No intake swap or even cylinder head upgrade was going to get the job done, so we simply pushed the easy button, literally. What better (or easier) way to add 100 hp than with a 100hp shot of nitrous?
In keeping with the low-buck nature of our adventure, we relied on an affordable and adjustable Sniper kit from NOS. The simple plate nitrous system was adjustable from 100-150 hp using the supplied jetting. Since our goal was to add 100 hp, we chose the jetting accordingly. For the uninitiated, nitrous adds power through the liberation of oxygen molecules. Once heated, the compound releases the oxygen molecules, which are free to burn with additional fuel. Add them in the proper proportion and you are rewarded with instant, pushbutton power. So, let’s see what fun our stack of parts can bring to the budget 4.8L party!
Photography by Richard Holdener