Project Number Cruncher is our first foray into building a car destined for serious bracket racing action. The Firebird will be powered by a 427 cubic-inch LS that the students at SAM Tech assembled using top-shelf parts. Today, we’re going to take a look at the parts we used for the short block of the engine and why we chose them.
Bracket racing is all about consistency and repeatability, so taking as many variables out of the equation as possible is critical. We wanted to build an engine that wouldn’t need a lot of maintenance but still make plenty of power. Instead of building your typical small-block Chevy, we partnered with Dart to create a healthy naturally-aspirated LS engine that didn’t use any exotic parts.
The next part of the equation was finding an engine builder for the job. SAM Tech has extensive LS engine experience and it’s training tomorrow’s engine builders. Jimmy Stray with SAM Tech explained how the school approached the build with its students.
“Whenever we look at building a new project the first things taken into consideration are the application and desired horsepower level of the engine. That will give us a good idea of the level of parts required to meet and exceed the performance expectations. The school’s goal is to teach the next generation of engine builders the skills required to build quality performance engines that not only exceed the owner’s expectations, but also last the test of time when it comes to longevity. This was the main goal with Number Cruncher, to build a solid foundation starting with the short block assembly.”
Project Number Cruncher’s LS engine is based around Dart’s cast iron LSNEXT blocks. In a previous article, we covered the advantages of this block and why we elected to use it. An aftermarket block provided SAM Tech with the perfect canvas to begin the engine build.
SAM Tech started by getting the ARP main studs put in place and completing the corresponding machine work. The goal of this is to ensure everything was round and straight. The ARP studs will make sure the caps are held securely. This process will also make sure the linear movement of the piston to the crankshaft’s rotational movement is optimized.
SAM Tech’s Andrew Hachmeister explains what other items were addressed during the block machining process.
“After the studs were added to the block and squared away, we machined the cylinder bores to final size. With the precision work from Dart our actual machining time was reduced for this process. A very important part in the honing process is cylindricity and creating the proper surface finish — sealing is the name of the game. Finally, we surfaced the block to the proper deck clearance and together with our head gasket choice provided us with the quench we were shooting for.”
Crank And Bearings
With the block finished, SAM Tech moved on to getting the crankshaft ready along with the bearings. For the backbone of this stout LS engine, we decided to use a Dart billet CCW crankshaft. The CCW stands for center counterweight, and that’s the exact reason we selected this crank. A CCW crank is ideal for high-RPM applications since it stiffens up the crankshaft and reduces how much a crankshaft will flex. That means the crank won’t start to “jump rope” under a high RPM or horsepower load. That will prevent it from walking inside the main caps and cause issues.
The crank we used has a 4.000-inch stroke, 58-tooth reluctor wheel, has a total of eight counterweights added, and is made of 4340 billet material. Dart also added heavy-duty rod cheeks and a small hole through the rod pin, the crank is rough balanced to 1780 grams, and it doesn’t require any Mallory (Mallory 300 is an alloy commonly used for crankshaft balancing).
“We decided to use the center counterweighted crank on this build, partially due to the amount of RPM that we will be turning. A proper crank is very important, especially when you get over 7,000 RPM. Choosing the center counterweight will allow more reliability for the life of the engine. The crankshaft came to us rough balanced, so we brought it into the proper spec that we desired based on the weight of the components. We polished the journals one more time and cleaned the crank up before installation. Once all the bearing clearances were checked, the ARP studs were torqued for the last time,” Hachmeister says.
Bearings play an important role in how an engine comes together and performs, so you need to make sure the ones you select are up to the task for your application. We opted for a full set of MAHLE bearings on this build; these will have no issues dealing with the horsepower or cylinder pressure we’re going to throw at them.
Dan Begle from MAHLE provides some insight into why good bearings are a must in a high-performance build like this.
“Performance bearings are able to withstand a higher load rating and crank deflection with less overlay fatigue than the standard replacement bearings. Performance bearings are designed to give more crush, too. This is important as the crank deflects due to torsional loads…it will want to move the main bearings.”
Begle dives further into bearing crush and why oil film is important.
“Increased crush will maximize the clamp load to the main bore to prevent this movement. It’s extremely important to have a bearing designed to improve oil film and maintain oil film like a performance bearing. With increased load, oil film can be compromised creating a bearing seizure. Having a bearing with a higher seizure resistance and load carrying capacity is crucial.”
Rods, Pistons, Rings, And Fasteners
The connecting rods that SAM Tech selected for Project Number Cruncher aren’t some exotic part, they’re literally off-the-shelf K1 6.125-inch rods. SAM Tech has put together plenty of record-setting all-motor and boosted LS engines, so there was no question this choice would work. These rods checked every box for our goals with the engine.
“K1 provides a very nice connecting rod — these will be well within our range of power and will withstand the RPM that we will be turning the engine at. Not only is it a nice rod for the application because of its strength and weight, but the tolerances are also right on par for what we would like to see,” Hachmeister says.
The bolt must keep the cap on the rod. The clamping load produced by the properly installed rod bolt must exceed the dynamic load that the cap sees at the maximum RPM. – Chris Raschke, ARP
A high-winding naturally-aspirated engine that’s making a lot of steam is going to be exposed to different loads and forces. That’s why it’s so vital to get the right rod for the application and ensure that you’re using the correct fastener. Matt Polena from K1 adds some additional information that explains why SAM Tech went with this particular rod and faster.
“Naturally-aspirated engines see a lot of on and offloading of the connecting rod, resulting in a lot of force pulling at the connecting rods. K1 rods are forged from 4340 steel and shot-peened to improve fatigue life and come with thicker blades to help minimize outward bowing at peak combustion pressures. With connecting rod bolts being the highest-stressed fastener in your engine, having ARP 2000 series bolts included in the K1 rod is a great benefit for a high-horsepower NA build like this one,” Polena explains.
Project Number Cruncher’s ARP hardware was provided by Summit Racing Equipment; even during a global pandemic Summit had everything we needed to button this short block up with the right fasteners. Summit does more than just sell parts, the company can answer any question you might have about the parts you need. Summit Racing Equipment’s Joe Fishel adds some additional information about why using the right fasteners is so important when you’re installing connecting rods.
“Quality fasteners are a requirement in any high horsepower engine build. Stress on a connecting rod isn’t so much from cylinder pressure as it is from the extreme reciprocating loads of high RPM. Thanks to the ARP rod bolts, the main caps are firmly clamped down and start to oval out. This prevents rod bearing failure, and can keep you from tossing a rod through the side of the block,” Fishel says.
SAM didn’t just bolt the K1 rods to the Dart crankshaft before moving along in the assembly process. The students had to do some prep work before the rods were installed, this is a critical step to make sure there are no issues when the engine is finished.
“Before we install rod bearings, first we have to ensure the housing size is the correct size. After we confirm they’re the proper spec, we installed the bearings and checked vertical oil clearance to ensure that there will be no issues. Once all clearances are matched up, we cleaned the crank journals and bearings for the final time, then use VP assembly lube in between the bearing and crank, finally, we torque the ARP bolts down,” Hachmeister explains.
Generally a N/A engine we want the piston to be able to run at the tightest clearance possible and rock as little as possible. Vic Ellinger, Wiseco
The Wiseco pistons for this build are the only custom part that needed to be used. Custom pistons for an engine build like this are a great idea because they can be tailored for the application based on the dome design, compression, and skirt that SAM wanted to see. These areas are important because they allow SAM to optimize the engine even more so the maximum amount of horsepower can be generated.
“Getting a custom set of pistons is especially important for a naturally-aspirated build. There is no outside source that you can turn up to create more power. Since this engine is naturally-aspirated the parts need to be lightweight and work together efficiently. Wiseco’s experience allows it to decide what is safe with the lightening of the piston so no strength is sacrificed,” Hachmeister says.
Vic Ellinger from Wiseco provides some background about what goes into designing a piston like the one he created for Project Number Cruncher’s engine.
“For naturally-aspirated engines, piston-to-wall clearances can generally run tighter due to less heat and horsepower being generated compared to an engine with a power adder,” Ellinger explains. “The barrel and cam incorporated into the shape of the piston can sometimes be more aggressive with less expansion. This can help stabilize the piston better and in turn increase ring seal and reduce wear.”
The final piece to the piston puzzle for Project Number Cruncher’s engine was the piston rings. SAM Tech elected to use a 1mm, 1mm, 2mm, and a gas ported top ring combination from Total Seal. This ring package was selected after looking at the stroke length of the engine and the goal RPM level to determine the piston speed.
Total Seal’s Lake Speed explains why this ring package will work with this particular engine package.
“Without power adders, a naturally-aspirated engine must operate efficiently to maximize power output per cubic inch. A 1mm, 1mm, 2mm ring package is a sporty yet conservative ring package for an N/A engine. It is light enough to enable high RPM, which lets the N/A engine stretch its legs. This is super important because over 40-percent of all engine friction comes from the piston rings rubbing against the cylinder bores, and engine friction increases with RPM. As such, going with thinner, lower tension rings unlocks horsepower and lets the engine make more power at higher RPM. All of this yields increased engine efficiency.”
The oiling demands of a high-horsepower LS engine are significant, so you need to make sure your pump and pan can flow plenty of oil. SAM Tech decided to use a Melling 10294 performance oil pump for this build because it has the right attributes for this application. The Dart block we’re using as the base for this engine presents a specific set of needs that need to be addressed to prevent oiling issues.
Mike Osterhaus from Melling explains why this pump was created.
“Engine builders using Dart’s LS Next with standard bearing clearances can see high oil pressure when using the Melling 10295 stock volume oil pump. When the Dart block was released, engine builders modified the oil pumps in a way to reduce the amount of oil flow from the pump,” Osterhaus says. “To properly address this issue, Melling released the 10294, a low-volume, standard pressure oil pump. The 10294 provides 15-percent less oil flow than the 10295, and should only be used with aftermarket blocks with priority main oiling. The 10294 comes with optional +10 and +25 psi pressure springs that are packaged with the pump to increase the pressure setting of the pump. The +25 psi spring was designed to match GM’s pressure setting for the COPO Camaro LSX engine.”
All of the oil that flows through the engine needs a place to hang out when it’s not being used, that’s where the oil pan comes in. High-horsepower N/A cars must have an oil pan that’s designed to work with the engine. There’s a lot that goes into making sure the engine’s oil is going to the right places at the right time.
“Having a proper oil pan can have a couple of big effects on the oil. Not only will the proper design shed oil off the rotating parts through its kick-out, but it will create a better quality of oil with less aeration. The baffles are very important and need to match the engine’s application. They make the oil stay inside a contained area to provide a constant oil supply while you’re going down the track, during braking, and cornering,” Hachmeister says.
Moroso makes some of the best oil pans on the market, and thankfully they had one that would work with our Dart block. Thor Schroeder from Moroso explains what the company looks at when it comes time to design a slick oil pan like the one we’re using.
“A good oil pan for an N/A engine will free up horsepower while cutting down on oil temperature by efficiently removing oil from the crank, and keeping it away from the crank once it is removed. That’s why many performance engine builds need an aftermarket oil pan with additional oil capacity, internal anti-slosh baffles, trap door baffles to control oil sloshing inside the pan, and a power kick out/pouch. This power kick out/pouch is an area on the side of a non-skirted engine oil pan that lets the oil vapors from the crank escape; this will free up horsepower and help with oil temps.”
Now that SAM Tech has the bottom end of Project Number Cruncher’s LS built it’s time to move on to the top end. In our next article, we will cover what went into finishing this engine before it gets bolted in between the fenders of the Firebird. Make sure you check out the Project Number Cruncher build page right here to follow the entire build of this bracket racing machine.