Strength Enhancement
With the GM LS7 and all other aftermarket blocks (including competing options such as resleeved factory blocks) set as the benchmarks for improvement, RHS engineers successfully designed a block strong enough to support 2,500 hp (given a skilled builder who incorporates plenty of other high-quality components in the engine, of course). That's a whole heck of a lot for an aluminum block, and it all starts with the company's selection of an A357-T6 aluminum alloy that gets subjected to a unique solidification and cooling process, including chilling of the main bearing bulkheads for added strength. After casting is complete, the block is CNC-machined, and here the same CAD tactic of "dynamic sectioning" that ensured adequate wall thickness during design of the block also helps achieve maximum precision during machining.
Up top, the strength of the head gasket seal is greatly improved thanks to a total of eight additional large head bolts per cylinder bank. Whereas factory LS blocks typically utilize only four large head bolts for each cylinder (making for a total of ten M11 bolts on each bank), the RHS LS Race Block uses six. All of this adds up to a total of eighteen large head bolts per cylinder bank, greatly increasing clamping of the cylinder head and thereby providing a more robust head gasket seal.
The cylinders themselves are stout as well. A Siamese bore is used to help accommodate this, but unlike some other aftermarket blocks, the water jacket encircles the bores as completely as possible (just like in the LS7). Press-in spun cast iron liners are super strong, and are claimed to be almost like a forging, as their casting process helps them receive the benefit of similar grain structure to that of a forged piece.
Despite all of these strength enhancements, Reese reports that the RHS block will weigh in at about 119 pounds, just a bit more than an LS7. And as just one more example of the engineered-in strength of the LS Race Block, rolled threads are utilized on every threaded hole, even those used to attach accessories. Now that's attention to detail!
Big-Cube Capability
Want additional inches out of your underhood beast? The RHS LS Race Block delivers. It's available in two deck heights: the standard 9.24-inch, as well as a 9.75-inch version (availability of even taller decks on a custom basis is pending). Taking a page from the "Olds Rocket Block" iteration of the SBC, a raised camshaft, along with the main oil gallery having been moved outward, allows up to a 4.60-inch stroke to be utilized without running into rod-to-block clearance problems, even with standard rod journal diameters. Unlike other aftermarket blocks, the ability to contain such a hefty stroke was not a design afterthought; it was intended from the very beginning. As to cylinder liner lengths, both standard deck (5.67/5.87-inch; same as the LS7) and tall deck (5.94/6.38-inch) versions are available, and big-inch builders know how critical this aspect can be to piston durability on long-stroke engines, where the piston can otherwise come too far out the bottom of the bore.
As for bore sizing, the RHS LS Race Block was designed to accommodate finished bore sizes ranging from 4.060 to 4.165-inches, and a thickness of 0.089-inch is maintained in those super-strong iron sleeves even at maximum bore-not to mention an additional .200 of aluminum behind it. Doing some simple math, it's easy to see that if you combine a 4.165-inch bore with a 4.60-inch stroke, you wind up with over 500 cubic inches of LS power!
Reese used a flow bench to...
Reese used a flow bench to test prototype LSXR runners. He points out the usefulness of a flow bench as well as its limitations: while actual measurement of static air flow, spatial measurement of velocity, and flow restriction/energy loss are possible, it can't evaluate any tuning effects. (It should also correlate with the results of the CFD analysis, otherwise that model will have to be tweaked.) And it is critical to note that while gains in dyno-measured airflow always result in more power, this is not necessarily true of improvements in flow bench airflow.
The FAST team's extensive...
The FAST team's extensive testing led to a longer, less restrictive runner design over stock intakes for the final product. As you can see, the LSXR yields 14 hp and 11 lb-ft on an otherwise-stock LS3, using a 102mm throttle body, with reported excellent driveability to boot.
Though not a finished product...
Though not a finished product in terms of machining, this RHS LS Race Block on display at the 2008 AETC conference gave us an up-close glimpse at some of the features that will surely help this block rank among the top of the heap as far as high-strength foundations for LS engines go. Check out the large "windows" cast into the valley area, yielding excellent access to the lifters as well as the additional upper head bolt for each cylinder.
The 0.388-inch raise in the...
The 0.388-inch raise in the RHS block's camshaft tunnel (shown here with unmachined lifter galleries) is easily accommodated with 2 extra timing chain links. Despite the raised cam, the valvetrain is kept as stable as possible; maximum pushrod angularity remains less than 2 degrees. An Ampco 45 cam thrust plate (which is obviously not shown here; made of a bronze material, it offers a little bit better wear characteristics versus the stock cast iron piece) and an aluminum rear cover are included with the block.
A view of the lower driver...
A view of the lower driver side of the block clearly shows the kicked-out nature of the main oil gallery running from the front to the back of the block. The tapped chunk of metal where a Gen IV knock sensor can mount is also visible, as are the generous feeds for dry-sump systems.
The LS Race Block's long-arm-friendly...
The LS Race Block's long-arm-friendly design and consequent large cubic inch capability are seen in this drawing depicting rod movement within the block. Even with an H-beam rod and 60mm cam, we have clearance, Clarence!