Rock Solid: Project Number Cruncher Gets A Dart Iron LSNEXT Block

Building an engine capable of generating high amounts of power for a drag racing application requires certain things — one of the biggest is durability. If you want an engine that’s going to deal with a lot of abuse you better have a quality block as the base of the build. For Project Number Cruncher we’re using one of Dart’s cast iron LSNEXT blocks so we can crank up the naturally-aspirated ponies.

The LS family of engines has proven itself time again as one of the most durable production mills in the world, with or without a power adder. There have been documented instances of the stock blocks making well into the four-figure horsepower range without batting an eye, however, they’re still OEM blocks, and they do have limits. Since Project Number Cruncher is going to be run hard and run often, and make nearly 800 naturally-aspirated ponies, we wanted to ensure there wouldn’t be any issues with the block, so it only made sense to go to an aftermarket unit for a solid foundation.

Dart looked at the entire LS engine block to see what could be improved before it started the design process for the LSNEXT block.

LSNEXT Block Basics

Dart has a rich history of producing aftermarket blocks that address the issues of factory blocks, and these improvements have allowed racers to make plenty of worry-free horsepower. For the LSNEXT cast-iron block Dart wanted to use what it had learned over the years to improve upon the LS engine.

When you order one of the LSNEXT blocks from Dart, it can be configured with different options based on your application. Since we’re building a 427 cubic-inch engine, we went with a 9.240-inch deck height and 4.125-inch cylinder bore. The block can be ordered with a maximum bore diameter of 4.185-inches. These blocks also can be ordered either skirted or non-skirted based on your needs. This means with a full-skirted block you can use the stock-style front and rear covers, along with a stock-style oil pan, since it retains that bolt pattern.

Kyle Scheel from Dart explains how Dart approached the design of the LSNEXT series of engine blocks.

“With this block, we wanted to fix what GM got wrong and produce a block capable of handling the most extreme racing conditions. We did away with factory features on these blocks that weren’t that good and improved other critical areas. You can even order these blocks with the finish machining done so it’s ready to assemble.”

Adding strength to the block was a priority for Dart from the start.

One of the first things Dart did with the LSNEXT block was upgrade the material to Class 30 cast iron — this gives the LSNEXT block more strength over the OEM block, and that means you can push the boundaries of performance. The bottom end is reinforced with main webbing to make sure it would have extra rigidity. Cylinder strength for an engine block becomes a factor when you’re really leaning on an engine, and Dart used extra thick Siamese cylinder bores in the LSNEXT block to make them stronger and allow them to be enlarged for engines that have bigger displacements.

“The main webs are significantly strengthened by closing off the bay-to-bay breathing holes that are present in the main webs of factory blocks. This is possible due to the main cap and oil pan rail redesign,” Scheel says.

The LSNEXT Difference

As we mentioned earlier, Dart made some significant changes to the design of the LSNEXT block to make it better than its OEM inspiration. Every one of these changes was introduced to address a deficiency Dart saw that took away from the block’s ability to produce horsepower or its long-term durability. The changes Dart made start at the top of the block and touch every area of the LSNEXT design.

Besides making changes to add strength to the block, Dart wanted to make sure the oiling system was improved versus the OEM design. This meant taking a fresh look at how oil was delivered in the engine to make sure all the important parts were getting the most lubrication possible.

With this block, we wanted to fix what GM got wrong and produce a block capable of handling the most extreme racing conditions. – Kyle Scheel, Dart Machinery

“The oiling system was changed to support priority main oiling. Doing this oils the most important engine components first: the crank and connecting rods. It reduces the oil volume requirements of the block and oil pump to improve the system overall. A provision for oil restrictors in the lifter valley was also added, as well — this is great for solid roller camshafts that some racers will use. The main web, main cap, and oil pan rail redesign all work together to dramatically reduce windage and parasitic horsepower loss that LS engines suffer from,” Scheel explains.

The oiling system for the LSNEXT block got a lot of attention from Dart. This led to a vastly improved design over the original OEM casting.

Working on improving how the engine’s vital components are fed lubricant is just one of the big changes Dart made to the LSNEXT block design. Dart saw an opportunity to optimize how the main caps interact with the block itself. By doing this, it adds to the overall strength of the block and assists the crankcase’s ability to breathe better.

“The main caps are made of billet steel and are of the four-bolt, splayed style. This style of cap, coupled with scalloping out the backside of the oil pan rail, greatly improves bay-to-bay breathing in the crankcase and allows for the previously mentioned main web improvements. There is no strength loss by utilizing the four-bolt, splayed cap over the factory six-bolt style main cap. The main caps are fastened to the block with a set of ARP 2000 main studs for optimal strength and clamping,” Scheel says.

One of the biggest improvements Dart made with the LSNEXT block pertains to the cylinder bore sleeve length. The OEM sleeve length is very short, so if you try to add a lot of stroke to a stock block engine, the lower part of the piston will actually be pulled totally out of the bore. That exposure will cause the piston to actually move over center and that will cause damage over time. To address this, Dart made sure the cylinder barrels extend a full .375-inches into the block. This additional length ensures the piston stays happy and gives you clearance for 4.100-inches of stroke if you want to build a gnarly engine with more displacement.

The increased sleeve length of the Dart LSNEXT block makes it a perfect candidate for a big cubic inch stroker engine.

On the top side of the LSNEXT block, Dart wanted to be sure you could use whatever style of cylinder head you wanted and upgrade the camshaft, too.

“The deck is 5/8-inch thick and has provisions for six-bolt style cylinder heads — this provides the most rigidity and superior clamping for high-horsepower and forced induction applications. The deck can also be upgraded to ½-inch head bolt holes over the standard 7/16-inch sized bolts. The block can support upgraded 60mm Babbit camshaft sizes, and larger lifter bore sizes that will accommodate a 1.060-inch lifter bushing,” Scheel explains.

Aftermarket Blocks For Drag Racing

As we mentioned earlier, an OEM LS block is upon to the task of handling virtually anything you can throw at it, but overall, it’s not designed specifically for drag racing like the LSNEXT block. The OEM block will have strength and durability issues at a certain point…what that point is will depend on the block you’re using. Another issue with an OEM block is that it won’t have the level of windage control and reduction of parasitic horsepower loss an aftermarket block will have. This is very important in a naturally-aspirated application like Project Number Cruncher.

Having a blank page to create its design gave Dart the ability to ensure the LSNEXT block’s deck would be super rigid. This is important because it provides the best surface possible for a head gasket to seal to — if you’re adding boost to the engine that is critical. An aftermarket block is also made of better material than its OEM counterpart, which means it can deal with heat and cylinder pressure much better — something you see in a nitrous application.

A stronger deck and extra cam options give racers plenty of choices when it comes to how they can use their Dart LSNEXT block.

Since we’re going to mostly be bracket and index racing Project Number Cruncher, going with a naturally-aspirated combination made the most sense. This is another case where an aftermarket block like the iron LSNEXT from Dart was the best fit for the job.

“The overall improved strength of the block means it will distort and flex less as it heat-soaks from seeing multiple runs. That means it will be a more consistent platform. We all know the value of consistency in bracket racing,” Scheel says.

The block’s critical machine work will be done by the School of Automotive Machinists & Technology. When it came time to look at what specifications were needed for this build, SAM Tech was consulted and it was decided for better performance we could run a larger lifter with the increased bore. In future articles, we will breakdown everything SAM Tech does to the entire engine to make it a nasty naturally aspirated beast.

So, as you can see, there are plenty of reasons to invest in an aftermarket block for a drag racing application. Engine blocks like the LSNEXT give a racer more options with how they want to build their engine, and they address the shortcomings of an OEM block. Make sure you follow the entire Project Number Cruncher series as we get our Firebird ready for some bracket racing action.

Article Sources

About the author

Brian Wagner

Spending his childhood at different race tracks around Ohio with his family’s 1967 Nova, Brian developed a true love for drag racing. When Brian is not writing, you can find him at the track as a crew chief, doing freelance photography, or beating on his nitrous-fed 2000 Trans Am.
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