We have been dreaming of ways to fully utilize the capabilities of the Concept Performance LSR block in one of our project vehicles since we laid eyes on it six years ago. Well, we finally have such a vehicle in LSX Mag’s Project McLuvin. We’re using the LSR block as the foundation for a Whipple-supercharged 427 cubic-inch LS build to power our all-wheel-drive 1976 Chevy Luv street terror. Upon receiving our LSR block, we wanted to compare it side-by-side with a factory GM 6.2L block and show our readers the differences.

More Than Just Another Aluminum Block

The Concept Performance LSR engine block is a premium aftermarket product for LS enthusiasts who want to build high-horsepower engines using an aluminum block. Traditionally, enthusiasts have chosen iron blocks for engine builds that see four-digit horsepower output. The reason is that iron is very strong and resists distortion under high loads. However, before you think the LSR is just an aluminum recreation of something like the iron LSX block, understand that Concept Performance has engineered its LSR block with even more strength and features.

Looking at the LSR, on the engine stand it’s apparent from any angle that this block is strong. There is reinforcing webbing and added thickness everywhere when compared to a factory 6.2L block.

The LSR block is cast in the USA using 356-T6 heat-treated aluminum with spun ductile iron sleeves and weighs only 113 pounds with its billet-steel main caps. Although the LSR is on par with the weight of a factory aluminum LS block, its horsepower capabilities far exceed any factory aluminum offering. Additionally, the LSR is over 100 pounds lighter than a comparable iron block. When deciding on the route to take with Project McLuvin, it was a no-brainer choosing the LSR over the factory 6.2L block we had in the shop, considering we expect our engine to be in the 1,200- to 1,400-horsepower range, and it will likely see a lot of heavy-footed use. We’re confident the LSR will have zero issues in our build considering these blocks are used on engines making 2,000-plus horsepower.

Stronger From Top To Bottom

One of the main advantages of the LSR block is its reinforced structure. It has significant cross-bracing in the lifter valley with triple bracing through the sides of the block. In addition, there are no windage windows found under the crank saddle like on other blocks. The LSR is solid through that area to create a stronger crank saddle, and a radius is machined where it meets the skirt wall. According to Concept Performance, this helps with strength by removing the sharp corner typically in that location on other blocks.

The strength improvements don’t stop there. The main caps are made from billet 1045 steel in either a six- or eight-bolt design and include ARP hardware. The eight-bolt main caps have a double cross-bolt configuration and a 40-percent larger main cap surface for enthusiasts that want to push the LSR to the max. This design increases the rigidity and durability of the block under high cylinder pressures to prevent distortion and cracking. Our LSR has the six-bolt main cap option, which is plenty strong for the power level we’re going for with boost from a Gen-5 3.0L Whipple supercharger.

Build It Your Way

Another benefit of the LSR block is its versatility and compatibility. It is offered in two deck heights depending on your needs: standard (9.240 inches) and tall (9.720 inches). The standard deck height matches the factory GM 6.2L engine block, while the tall-deck-height block has a raised cam bore and allows for more stroke and displacement options. Because we are keeping the displacement to 427 cubic inches, we opted for the standard deck height. All LSR blocks feature a six-bolt cylinder head pattern and can also accept standard four-bolt cylinder heads. Additionally, all OEM LSX parts, such as covers, pans, and accessories, work seamlessly with the LSR block.

A design feature we found to be much appreciated is the access area in the lifter valley. These windows allow for the removal of the lifters without needing to remove the cylinder heads. If a lifter needs replacing, only the intake and valley cover are removed to gain access to the lifters. Speaking of lifters, the bore comes standard sized but can be machined to accept lifter bushings as large as .904-inch. They can also be machined for keyway-style lifters if desired.

The LSR can accept a maximum bore size of 4.200 inches. Combined with a maximum stroke of 4.250 inches on the standard-deck block, you could have a whopping 467 cubic inches of displacement. As much as a big cubic inch build intrigues us, we are using a 4.125-inch bore and a 4.000-inch stroke in our engine build to be at 427 cubic inches.

What The Future Holds For Our LSR Block

For our project, it is important to point out that the LSR has a seventh transmission bolt-hole on the back side of the block. This opens up our choices to pre-LS transmissions. We have not completely settled on a gearbox yet, but it’s nice to know we can use anything from a two-speed Powerglide to an electronic ten-speed, or a manual transmission if we decide to row the gears ourselves.

Now that we have our hands on the LSR block and can see up close all of the improvements and features that Concept Performance has designed into it we are excited to get our engine assembled and fired up. Currently, we have everything for our short-block assembly at our engine builder being machined and prepped to go together. As we get closer to our supercharged 427 LSR being completed and ready to dyno we will bring you updates. So check LSX Mag often as we make progress on getting this LSR monster in Project McLuvin.