Recently, the editor of one of our sister publications — Off Road Xtreme — reached out to ask about an engine build for one of their more badass projects: Project Resurrection. The truck is planned to go full off-road beast mode, and the team wanted a powerplant to match the rest of the build.
After some discussion, we had a pretty general game plan to put together a centrifugally supercharged combination based on the engine platform the 2002 Chevrolet Avalanche came with: the ubiquitous 5.3-liter LS. While we jumped at the opportunity to help out the team, we quickly realized that our familiarity with the LS engine alone wasn’t enough to get us through the project properly.
When it comes to off-road performance, there are a lot of nuances that don’t appear in other forms of motorsports. Just like circle track, drag racing, and road racing can each pose specific issues, so can off-roading. Loading and unloading the engine as the drive wheels leave the surface, crazy G-forces as the vehicle slides around the dirt, bangs over whoops, or leaves terra firma altogether can have adverse effects on the engine’s systems.
So, we reached out to Bruce McKillop of CBM Motorsports of Colton, California. CBM lives in the part of the Venn diagram where “LS Engines” and “Off-Road Performance” overlap, as they specialize in both. Together, we talked about what works and what doesn’t in an off-road application and assembled a build plan for an engine that is both badass, reliable, and absolutely attainable by anyone who is interested.
That means no super-expensive or exotic, unobtainable parts or secret “trick” machining. Nothing in this build was chosen just for the sake of being fancy. Rather, we decided on good, solid parts that all work together for the desired performance goals without breaking the bank, or anything else for that matter. Here, we’ll cover the bottom-end of Resurrection’s engine build.
Iron blocks are better for boost, as you get less cylinder shift [under boost] in an iron block. — Bruce McKillop, CBM Motorsports
An OEM Foundation
Since the 2002 model-year Avalanche we’re working with isn’t the Z71 package, it was originally equipped with a Gen-III 5.3-liter LM7 iron-block engine making 285 horsepower. That comes in 0.882 horsepower per cubic inch (or 53.8 horsepower per liter) — not exactly stellar numbers. Since our goal is to increase that number by about 250-percent, having a solid foundation is critical.
No one has ever accused an iron-block LS of not being able to handle boost, and the 5.3-liter iron block has proven to be capable of huge numbers in a myriad of applications, and the off-road arena is no different. The 5.3-liter bock is actually so reliable, we decided to open the bores a massive .118-inch, each.
That much overbore in a factory block would be absolutely unheard of in previous generations of small-block Chevrolet engines, but the LS engines are a different story. That .118 inch takes the bore size from the stock 3.780-inch diameter to 3.898 inches. If you are an LS fan, that number might look very familiar — it’s the stock LS1 bore diameter. Since the LS1 uses the same stroke as the 5.3-liter LS family, we now have an iron-block 5.7-liter LS.
“This is actually a very common practice because there is no extra cost to increase the engine’s displacement,” says McKillop. “More cubic inches equals more horsepower.” The benefits for the project are more than just simply more displacement for only the cost of machine work, as opposed to a brand new crank.
First, the additional bore size helps to unshroud the valves and improve flow into the cylinder. Second, by using a common bore size — like that of the LS1 — our off-the-shelf piston options become substantially larger. As one of the most popular platforms on the market, piston selection for 3.898-inch bores is almost overwhelming. That means no custom orders and the associated costs and wait times were needed for our project.
Now, you might be wondering why we wouldn’t just start with an LS1 block if we wanted more bore diameter. First, have you actually looked at what kind of prices aluminum LS1 blocks are commanding on the used market these days? They’re insane. Additionally, there’s something to be said about dancing with the one that brought you, and when you start with an iron 5.3-liter engine, it’s much cheaper to bore out the block you have, than to buy something new, used or not.
Then, there is the matter of the material itself. “Iron blocks are better for boost, as you get less cylinder shift [under boost] in an iron block,” explains McKillop. However, he does point out that aluminum radiates heat better than iron, but in our application, that shouldn’t be an issue. Since the engine was running when it came out of the truck, there wasn’t a whole lot of machining required to get the block ready.
“For this particular build, the bores were opened up, the surface was decked, and we checked the main bore alignment. It was actually a pretty simple trip through the machine shop,” McKillop commented. So, with the block ready to go, it was time to move on to the other components.
5.7-Liter OEM Rotating Components
As was mentioned earlier, the stock 5.3L crankshaft was used. A cast nodular iron piece, the OEM Gen-III crankshaft features a 3.622-inch stroke length, which is shared by the entire 5.3-liter family, as well as the 5.7-liter, 6.0-liter, and 6.2-liter Gen-III and IV variants (even the Gen-V LT family uses a 3.622-inch stroke length). In fact, the only factory LS engines to not share the 3.622-inch stroke are the 4.8-liter and 7.0-liter engines.
These OEM crankshafts have proven their mettle across a variety of setups in CBM’s extensive experience, so there was no hesitation to keep the factory unit. “We have used stock crankshafts safely to around 800 horsepower with a blower and up to 1000 horsepower with twin-turbo setups,” says McKillop. The Gen-III crankshafts come with a two-piece 24-tooth reluctor wheel on them from the factory, which should be fine for our project.
Connecting The Dots
While the internet is abuzz with stories of stock LS rods handling tons of power, first, it’s the internet and should be taken with a grain of salt. Second, those are the beefed-up Gen-IV rods, not the Gen-III rod in this LM7 from the factory. So, fitting with the theme of our project, we wanted a set of robust, reliable connecting rods which will withstand the rigors of not only the boost we’ll be force-feeding the cylinders, but also handle the challenges of driving in the dirt.
McKillop specifically called out Callies H-beam Compstar rods for this build, as these are what he uses in similar (and not so similar) customer builds on a regular basis. The Compstar H-beam rods are forged from 4340 steel and we opted for the 6.125-inch center-to-center rod length. That is slightly longer than the stock 6.098-inch length, and the most common aftermarket LS rod length on the market.
Designed to be an all-in-one part number that combines the quality you’ve come to expect from Callies with an affordable price tag the Compstar rods incorporate the “optional” features of other rods into every Compstar rod, making it easy to choose the right rod for your application. The rods we used (P/N: CSC6125DS2A2AH) use the factory 2.100-inch rod journal diameter but opt for the more common aftermarket .927-inch wrist pin diameter.
The Compstar LS rods come standard with ARP2000 bolts, which offer an exceptional tensile strength of 200,000 psi, along with revised bolt locations to provide additional stroke clearance without compromising on overall strength. Part of the way that is achieved is through the use of strengthening gussets at key points of the rod cap, as well as through FEA-designed contouring of low-stress areas.
That same method is used to reduce the weight of the Compstar rods without affecting overall strength or rigidity. By being able to locate extraneous material in the rod design through computer modeling and simulation, they can safely remove it. That brings down the weight of each of our rods to only 618 grams. “These are excellent entry-level forged rods,” McKillop says. “We have used them in the 1,500-horsepower range on turbo applications before.”
Get In The Hole
As we mentioned earlier, we went with a 3.898-inch bore specifically to be able to have access to the wide variety of shelf-stock LS1 piston designs. Right off the bat, McKillop specified 2618 pistons for this application. 2618 Aluminum offers a lower silicon content than 4032, which adds both tensile and yield strength to the piston while also making it less prone to cracking, which are all benefits when using a power adder.
As we started running the numbers on the combination to come up with the desired piston spec we came up with a list of specs, and sure enough, there was the exact piston sitting right there in the Mahle catalog under P/N: 930218798 as a complete PowerPak assembly. The piston is a flat top design with 2.200-inch intake and 1.700-inch diameter valve reliefs which measure a total of 4.1cc of volume.
There is no doubt 2618 can handle the power and the extreme RPM that occur in off-roading. — Joe Maylish, Mahle Motorsports
Forged from 2618 aluminum, the piston features Mahle’s signature gray phosphate dry-lube coating to reduce micro-welding and wrist pin galling, along with Mahle’s Grafal skirt coating that reduces drag, skirt, and bore wear, and can reduce piston noise, which is especially useful in the higher-expanding 2618 application. The 1.304 compression height gives us a perfect zero deck situation with the 6.125-inch rods.
“The 2618 alloy is what we use with high horsepower applications and even applications in drag racing that want to produce 2,000 horsepower,” says Mahle’s Joe Maylish. “So there is no doubt it can handle the power and the extreme RPM that occur in off-roading, whether the engine is wide open on the road or looking for torque and high RPM in silt.”
Included in the PowerPak are a set of high-performance piston rings consisting of a low-drag HV385-coated steel 1.0mm top ring, 1.0mm Napier second ring, and 2.0mm oil control ring, as well as lightweight, high-strength .927-inch steel wrist pins and heavy-duty round-wire locks.
Maintaining Your Bearing
When it came time for bearing choice, we reached out to King Engine Bearings and sent them over the parameters the engine would be operating in, and asked for their recommendation on which line of bearings we should use. King’s Vadim Golinski felt that their line of HP-series bi-metal aluminum bearings would be the right fit.
The HP-series is designed specifically for high-load, short-duration operating conditions, as well as power adder use. The silicon-aluminum material also features high-embeddability to deal with oil contaminants (like you might see in off-road conditions), which makes them ideal for our application. Additionally, the HP-series is noted as working well for performance applications using nodular iron cast crankshafts – again, exactly what we’re using here.
For the main bearings, we utilized the standard size, standard clearance P/N: MB5013HP half-groove bearings. The same went for the HP-series rod bearings as far as standard sizing and clearance, but with P/N: CR807HPN. For the cam bearings, they were also from the HP-Series lineup, but with a couple of differences, due to the type of bearing. P/N: CS5503HPT are performance bi-metal cam bearings, but made from a fluoropolymer-coated lead-based babbit composition on top of seamless steel tubing instead of the other bearings silicon aluminum composition.
Like a Well-Oiled Machine
When it comes to the oiling system on this engine, it’s almost shockingly simple. While you’d expect an engine going into a project like this to have some kind of fancy oil pan, McKillop went the opposite route, reusing the stock oil pan and LS windage tray. “They are pretty robust,” says McKillop of the stock pan. “Because there are so many different shapes and sizes you can usually find one that will fit in your application.” Since this oil pan came out of the truck, we know it’s sure to fit going back in.
To keep the oil flowing a Melling oil pump was used. If you’ve looked up an LS oil pump lately, you know there are a large number of options in the Melling catalog. For this setup, McKillop wanted both additional pressure and volume, which meant the P/N: 10296 pump. “We don’t want a ton more pressure or volume, and the 10296 offers a little bit more of each,” McKillop explains.
To seal everything up on the bottom end, we used Cometic’s LS Street Pro Bottom End Kit (P/N: PRO1036B). The kit includes front and rear timing cover gaskets, front and rear main seals, oil pan gaskets, water pump gaskets, a cam plate gasket, and more. Each gasket is made from one of Cometic’s wide variety of gasket materials, individually selected for its properties in that specific application.
With that, the short-block for Project Resurrection is complete. Make sure to check back next month as we cover the top end and valvetrain components chosen for the engine and bring you the completion of the long-block in preparation for the crown jewel of the project, a ProCharger centrifugal supercharger.