Building A Forged 5.3 LS For Boost (2024)

The junkyard LS engine’s ability to generate big horsepower thanks to boost is well documented. There’s plenty of recipes out there that spell out how to make 800 horsepower or more using OEM parts, but there is a limit to what these parts can do. If you’ve got a little extra budget for your boosted LS engine build, using upgraded parts will go a long way to ensuring the engine will last a long time.

We plan on stuffing a turbocharged 5.3 LS engine into the Project Swedish Meatball Volvo. The block and heads were snagged from the scrap pile and were thoroughly gone through at RPM Engine & Machine. Now, we also wanted to be sure the rotating assembly and other parts of the engine were going to be reliable.

The reliability of the engine is going to be increased thanks to the new Summit Racing Pro LS rotating assembly, parts from Melling, ARP fasteners, ATI balancer, and Brian Tooley Racing valve train parts. In this article, we’re going to cover the short block assembly that was taken care of by Big 3 Racing after RPM Engine and Machine completed the machine work. We’ll dive into the rest of the engine build and other parts of the project in future articles.

A Strong Backbone With Summit’s Pro LS Rotating Assembly

We didn’t see a need to get super exotic with this engine build by using a ton of one-off parts. The Summit Racing Pro LS rotating assembly comes with a forged crank, rods, pistons, bearings, and piston rings. Summit rotating assemblies are commonly used in builds that touch the 1,200 to 1,800 horsepower range, so it will be more than enough for our little stock-displacement 5.3-liter LS.

Let’s take a look at the crank that Summit includes with these rotating assemblies. The cranks are made from 4340 forged steel and are offered in various stroke options with a 24X or 58X reluctor wheel. Each crank is core-hardened to optimize strength. They’re also tempered, and nitride surface hardened. The rod journals are lightened and the mains are gun-drilled as well.

The counterweights are profiled to reduce windage and improve engine acceleration. These cranks also feature straight-shot oiling so they can provide maximum oil flow where it’s needed most. Most important, the journals are consistently sized with an excellent finish and no taper. This makes setting bearing clearance easy and repeatable.

One of the big advantages to the forged crank Summit includes is its core hardness. Brian Nutter from Summit Racing talks about why the crank hardness is so important.

“While many aftermarket cranks are nitride surface hardened to varying depths, not all aftermarket cranks have the same core hardness,” says Nutter, “Lack of core hardness can manifest itself in a couple of ways. With supercharged engines, broken or bent snouts from high belt tension can occur. With high-RPM turbo engines, crank-whip can take out the main bearings toward the center. Center-counterweight cranks are an option, but they, too, need to have the correct core hardness. All in all, forged cranks are a great piece of insurance that ensures your engine lasts with big boost and power.”

OEM connecting rods are good up to a certain point. Gen-III LS rods aren’t as robust as the Gen-IV rods, and use weaker rod bolts, hence why people will use the Gen-IV rods in a build. The Gen-IV rods do have their own weaknesses, and are known to bend under boost. These are all problems that we wanted to avoid, and why it made sense to go with aftermarket rods like the ones included in the Summit Pro LS rotating assembly.

The Summit Pro LS H-beam connecting rods are made from 4340 forged steel. ARP 2000 rod bolts are standard-issue fasteners on each of the rods to maximize clamping strength. The rod caps are dual-ribbed for increased strength. The rods come with a precision-honed full-floating wrist-pin bore, and the big end is finished to plus-or-minus .0001-inch.

According to Nutter, Summit was very deliberate with its design of these H-beam rods to maximize strength in all the right places for boosted applications.

“Other H-beams may appear similar in profile, but Summit Pro LS rods have greater cross-sectional thickness,”Nutter explains. “They have a gentler radius in the center of the beam and this produces thicker blades. The rods have the right amount of material in the right places, and that’s what makes them strong.”

The final big piece of the rotating assembly puzzle are the pistons. In boosted junkyard LS builds, the pistons are considered the weak point and tend to fail first. This is due to design and material issues, they have their limits. It was an easy choice for us to move to forged pistons to avoid these types of problems, and keep our engine healthy for the long haul.

Summit Pro LS pistons that came in our kit (P/N SUM-R5836L7852) are made of a ductile 2618 alloy that’s more forgiving than other alloys when it comes to boost. Pressure-fed pin-oiling was built into the piston design and robust wristpins are included with the Summit Pro LS units. The domed pistons offer optimized valve reliefs that work with cathedral and rectangular port cylinder heads.

The recommended piston-to-wall clearance is .0040 inch in a stock block application. The piston skirt profile (cam and taper) is minimized to ensure maximum stability at the bottom of the stroke with 4.00-inch- -stroker combinations.

“Pro LS pistons have the best strength-to-weight ratio on the market. People have a tendency to throw in brick-like pistons at the 2,000-horsepower mark. Not only does it require a lot of expensive heavy metal to balance, it also stresses out the pins, rods, crank, bearings, and block. The 2.250-inch-long-pin strutted forging has been in tens of thousands of race engines over the years, and the structure just doesn’t fail,” Nutter states.

Ring lands are the common area where OEM pistons fail in a boosted LS application. “The goal with our pistons was to make sure the ring land area was strong,” says Nutter. “We optimized the thickness of the piston ring lands through improved 1.2mm ring packs. Summit Pro LS top ring-land thickness is in the .275 to .300 inch range. You’ll find the second ring land is a stout .165 inch thick.”

Each of the Summit Pro LS kits comes with Total Seal piston rings that are 1.5, 1.5, and 3.0mm The rings were gapped to .025-inches on the top and .027-inches on the bottom for boost.

Other Short Block Bits And Pieces

There are a few other parts that are getting bolted up to the engine as part of the short block. Instead of recycling previously used parts, we decided to invest in new gear to ensure the engine would last for many miles. Since the Volvo will also see some track time, we wanted that peace of mind knowing the parts we use could stand up to the abuse.

Proper lubrication is important to any high-performance engine, add a turbo to the mix and you better be sure the oil pump you choose is up to the task. Boost really increases the demand put on the oiling system. Turbos require lubrication from the oiling system, and the OEM oil pump isn’t designed to provide that additional volume. This is why we decided to use a new high pressure oil pump from Melling (P/N 10296) on our boosted 5.3 mill.

“Boosted engines in many cases will have extra bearing clearance added during the build allowing for more oil fill between the bearings and journals of the crankshaft,” explains Melling’s Cale Risinger. “This extra oil clearance helps to protect the rotating assembly against the added downward forces associated with the increased cylinder pressures that are present in boosted engines. An OEM pump from the junkyard isn’t optimal to provide lubrication for this situation, an aftermarket oil pump can.”

The timing chain set that was included with the 5.3 we pulled out of the junkyard won’t be used in this build. Who knows how many miles were on it and how much it had been abused? Melling makes really nice timing chain sets as well as other engine parts. We’re using one of these adjustable timing chain sets (P/N 48561T-9) on this engine, and will have a more detailed article covering why it’s a solid part to use in a future article.

When you’re putting together an LS engine that came from the junkyard, one of the first things you need to do is throw away all of the torque-to-yield fasteners. These fasteners were designed to deal with OEMhorsepower loads, and aren’t resuable anyway. You can exceed that power evel to a certain degree, with new OEM fasteners, if you’re brave, but it creates a potential failure point. Adding boost is going to increase the strain to unacceptable levels.

We used the industry-standard when it comes to fasteners and studs for this engine from ARP. The fasteners that ARP produces are rated at significantly increased tensile strengths over the OE fasteners. We used ARP’s head stud kit (P/N 234-4110), main stud kit (P/N 234-5608), and engine & accessory bolt kit (P/N 534-9705) for our engine.

“Boosting an engine increases combustion pressure dramatically. Higher-strength fasteners are essential for increasing clamping load and maintaining the head-gasket seal. The added power also translates to increased loads on the engine’s rotating assembly. To provide the needed bottom-end rigidity, upgraded rod bolts, main cap bolts, and studs are essential,” says Bob Florine from ARP.

If the engine you snag from the junkyard might still have a balancer on the end of the crank, it won’t be suitable for a turbo build. The 5.3-liter LS was rated for well under the amount of horsepower we’re going to generate with this turbo setup. That OEM balancer wasn’t tuned to handle the increased harmonics from the elevated level of horsepower. In short, that OEM balancer is a ticking time bomb on the end of the crankshaft if you try and reuse it, and that’s why we replaced ours with a unit from ATI.

“The OEM units are tuned by engineers to work best in a small RPM window that they perceive the owner of the vehicle, with a stock engine, would spend the most time in,” says ATI’s JC Beattie. You also have no guarantee the outside ring will not let go and spin under the added stress. The OEM dampers are also made of a very soft, cheap, easy-to-machine type of cast-iron called Meehanite. Of course, they can never be overhauled or have any parts changed if something were to happen to it.”

The ATI harmonic damper is going to eliminate the increased torsional crankshaft vibrations produced by the engine. ATI machines its dampers out of high-grade aluminum and steel so they’re much more robust than the OEM units. Another advantage to the ATI dampers is they can be tuned and are rebuildable. This saves you from having to buy another damper if you change the engine combination, or just want to have it maintained during the engine’s life cycle.

Now that the short-block is buttoned up for Project Swedish Meatball, it’s time to move on to the top end of the engine. Stay tuned as we continue to knock out the punch list for the Meatball so we can start ripping gears soon.