One of the staples of the LS-platform is the engine’s ability to make ungodly amounts of power and do so reliably. But even though all LS motors are renowned for their durability, it’s the iron-block examples that really shine in this respect.
In particular, the 4.8-liter LR4 stands out as being especially resilient. Unfortunately, however – despite its appetite for power – the LR4 tends to be a relative underdog in the LS-family. Whereas everyone and their grandmother is familiar with the LSx mills such as the LS1, LS6, and so on (and even the 5.3-liter Vortec motors receive praise as a low-cost alternatives), the smaller, 4.8-liter LR4 is often passed over.It’s understandable that someone would opt for the 5.3-liter over the 4.8-liter, thinking that with the extra half-liter of displacement they’re making a better choice for putting down bigger numbers in the future. However, the reality is that the LR4 is far more suited for reigning in big power than its 5.3-liter counterparts.
This is due to the fact that the 4.8-liter LR4 and the 5.3-liter LM7 (and it’s variants, the L59, LM4 and L33) share the same architecture; the same block and heads are found in both motors, with the only difference being the 5.3-liter utilizing a longer stroke.
This translates into a greater amount of material and thus better containment in the LR4 versus the 5.3-liter engines. Consequently, the LR4 can withstand incredible amounts of boost and horsepower while requiring a relatively minor amount of hardware upgrades. One of the more dramatic examples of this is Tim Underwood’s boosted-LR4 Camaro.
Tim purchased himself an F-body Camaro in late 2008 from a dealership near his Newark, Ohio home. A complete tuning car, the machine was in pristine condition (with only 54,000 miles) and was equipped with a full turbo kit and a Turbonetics snail. But, despite having a clean, professionally-modified street car, it was only a matter of time before Tim had to up the ante – and that he certainly did.After seven years of trial-and-error, Tim’s F-body Camaro is sitting at the hefty 827 wheel-horsepower and 728 lb/ft of wheel-torque it so furiously laid down in the above video. How did it accomplish such numbers? By pumping nearly 19 pounds of boost through its stock-bottom-end, stock-head LR4.
While these numbers are unarguably impressive – especially coming from one of the smallest-displacement small-blocks GM ever produced – Tim didn’t achieve this on his first try. Four other motors before the LR4 sat under his Camaro’s hood.Tim tells us, “The car’s original LS1 let go back in 2010, after which I put in a bone-stock junkyard 5.3-liter. A year later, I opted to attempt a build on a 6.0-liter and Precision PT88 combo that ended up not working out.”
After that combo didn’t work out, Tim switched to the tried-and-true 5.3-liter.
“I then went back to another 5.3-liter with the PT88 turbo and made 760 horsepower and 625 lb/ft on 17.6 pounds of boost, running 93-octane,” Tim said. “This motor had a bone-stock bottom end – I did zero disassembly on the rotating assembly – with head studs, 317 heads, upgraded spring retainers and upgraded pushrods.”
And while the 5.3-liter engine held together, the turbo decided to let go.
“The PT88 turbo ended up failing and a Comp 7879 unit replaced it,” Tim said. “With this turbo, the motor only made 655 horsepower and 685 lb/ft on 93-octane. Ultimately, it ended up melting a piston at the track when it was pushing over 28 pounds of boost while tuned for only 20 pounds.”
Tim continued, “I then made the decision to go with a 4.8-liter LR4 because a lot of Mustang-owners complain about LS motors being much larger than a GT power plant. The LR4 is the closest I could get to Ford’s 4.6-liter.”
“With the LR4, I made the switch to E85 and moved up to 706 heads. These heads have smaller intake valves than the those of the 317 heads I used before, but they also help increase compression over the 317 heads.”
Tim explained that the only work that the LR4 has received is the upgrade to the 706 heads (plus a stud conversion), upgraded camshaft, LS9 head gaskets, and the push rod, valve spring and titanium retainer upgrades. Another Precision PT88 supplies the boost, which Tim converted to a 91-mm unit to produce a healthy 18.6 psi.
The above video demonstrates just how much can be squeezed out of the relative tiny 4.8-liter Vortec motors – which originally produced a measly 250-280 horsepower and propelled GM’s early-2000s trucks. And, even though he only drives it a few times a month, Tim’s Camaro has been handling all of this boost and horsepower for almost a full year now.
As the icing on the cake, Tim is able to do almost all his own work. He states that when the Camaro’s original LS1 gave out, it was his first time ever dealing with a project of that magnitude; he had never pulled a motor out of anything before. However, the swap simplicity from both the LS1 to the 5.3-liter and later to the LR4 made everything doable – even in his garage, without a lift.While Brian Turner, the owner of Dynotune Motorsports, handles all of the tuning, Alex Lindner, the owner of BP Autosports, helps out with any welding; the chance to tackle every swap on his own has been a huge learning experience for Tim. He explained that the stress involved wasn’t always fun, but when it all comes together, it makes everything worth it. And after all, that’s the whole point of working on your own machine.
So next time someone comments on LS engines being inefficient or only making power because of their large displacements, pick yourself up an LR4 (there’s examples out there for less then $400) and you could be making nearly 3 horsepower per cubic-inch like Tim. How’s that for efficiency?