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554 hp From a Low-Buck Junkyard 4.8L LR4 LS!

Big power gains from simple mods on a 4.8L LS

Richard Holdener Jan 30, 2019
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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!

002 LR4 LS Junkyard Salvage Cam Swap Nitrous 2/16

You will remember that our adventure started out at a local wrecking yard with what we thought was a 5.3L LM7. In fact, the junkyard jewel turned out to be the smaller 4.8L LR4.

003 LR4 LS Junkyard Salvage Cam Swap Nitrous 3/16

Off came the factory EFI truck manifold to make room for our carbureted induction system. The well-used engine required a serious cleaning before we could install the new intake. Since we thought we were dealing with a 5.3L, we had a Victor Jr intake lined up. Had we known we would have run a dual-plane intake. The fuel was supplied by a 650-cfm Holley Brawler carburetor.

004 LR4 LS Junkyard Salvage Cam Swap Nitrous 4/16

Spark energy for the carbureted LS came from this MSD ignition controller. The MSD unit allowed us to dial in our ignition timing curve to optimize power production.

005 LR4 LS Junkyard Salvage Cam Swap Nitrous 5/16

Run with the carbureted induction system and through some “a bit too big” 1 7/8-inch Hooker headers, the otherwise stock 4.8L produced 331 hp at 6,200 rpm and 316 lb-ft at 4,900 rpm.

006 LR4 LS Junkyard Salvage Cam Swap Nitrous 6/16

The best way to improve power production on any LS, including our little LR4 variant, is to install a performance cam. We chose a Comp stick that offered a 0.614/0.624-inch lift split, a 227/243-degree duration split, and 113-degree LSA.

007 LR4 LS Junkyard Salvage Cam Swap Nitrous 7/16

The cam was installed with a set of beehive valvesprings. The stock truck springs were inadequate for the combination of high lift and extended rpm offered by the Comp cam.

008 LR4 LS Junkyard Salvage Cam Swap Nitrous 8/16

We used this dual spring compressor (from Comp Cams) to remove and replace the valvesprings on the LR4. Check out the sludge buildup evident on the factory springs.

009 LR4 LS Junkyard Salvage Cam Swap Nitrous 9/16

Out came the wimpy, factory LR4 cam and in went the aggressive Comp grind. This 4.8L was in dire need of a serious hot tanking.

010 LR4 LS Junkyard Salvage Cam Swap Nitrous 10/16

Run with the Comp cam and new springs, the 4.8L responded with peak numbers of 441 hp at 7,000 rpm and 354 lb-ft of torque at 5,400 rpm.

011 LR4 LS Junkyard Salvage Cam Swap Nitrous 11/16

These are the kinds of power gains enthusiasts dream about. Any time you improve the power output by over 100 hp, you know you have done something right. Equipped with the stock cam, the carbureted 4.8L produced 331 hp and 316 lb-ft of torque. After installation of the bigger cam, the power output jumped to 441 hp and 354 lb-ft of torque. The cam swap pushed peak power up by 800 rpm, to a peak at 7,000 rpm, while the torque peak shifted by 500 rpm (from 4,900 to 5,400 rpm). We love the sound of a little 4.8L at 7,000 rpm!

012 LR4 LS Junkyard Salvage Cam Swap Nitrous 12/16

To push our 4.8L even further, we installed this Sniper, dual-bar plate nitrous system from NOS. The Sniper kit included everything we needed to install the carbureted plate system on our little 4.8L. The kit featured a plate with dual spray bars to evenly distribute the nitrous and fuel.

013 LR4 LS Junkyard Salvage Cam Swap Nitrous 13/16

The Sniper nitrous system featured nitrous and fuel solenoids capable of supporting 150 hp. The Sniper system was adjustable using the supplied jetting. The solenoids and supplied high-pressure lines attached to the plates and sandwiched the nitrous and fuel jets.

014 LR4 LS Junkyard Salvage Cam Swap Nitrous 14/16

The power gains offered by any nitrous system are a function of the nitrous flow from the bottle, and flow is directly related to pressure. Given this, we made sure to dial in the fuel pressure supply line to the fuel solenoid (adjusted to working pressure of 5.75 psi), then heated the nitrous bottle to produce 1,000 psi. This ensured plenty of nitrous flow to the system. Gotta love them physics!

015 LR4 LS Junkyard Salvage Cam Swap Nitrous 15/16

Using the MSD controller, we retarded the ignition timing by four degrees. With the timing knocked down a bit we were ready to fire up the 4.8L on the dyno and hit the go button on the nitrous.

016 LR4 LS Junkyard Salvage Cam Swap Nitrous 16/16

The affordable Sniper nitrous kit was perfect for our low-buck, junkyard engine. Run with jetting to provide an extra 100 hp, the Sniper kit increased the power output of the 4.8L from 441 hp and 354 lb-ft of torque to an impressive 554 hp and 501 lb-ft of torque. Equipped with the cam and nitrous, this 4.8L was starting to make some serious steam now! But, as always, we still want a bit more.

Photography by Richard Holdener


Comp Cams
Memphis, TN 38118
Torrance, CA 90503
El Paso,



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