LSX Bowtie Block - LS Extreme

GM Performance Parts unleashes the super-strong--and affordable--LSX block

Rick Jensen Dec 6, 2006 0 Comment(s)

Every GM aficionado knows that factory engine blocks have practical limits, both in terms of durability as well as displacement. Although production LS1 and related Gen III and IV family engine blocks have enjoyed a relative excellent track record since their 1997 model year debut, cubic inches and longevity have come into question for more extreme horsepower applications. Until recently, the only solution to this dilemma was to plunk down about six thousand dollars for a C5R block; and while this option has certainly been viable for a corporate-sponsored race team, it has not normally been financially feasible for the average big-boost street/strip Z28. The fact of the matter is, as more and more enthusiasts encounter the limits of factory aluminum and iron blocks, the collective desire for an affordable, high-strength, big-inch casting has grown tremendously.

This need hasn't gone unnoticed by the aftermarket. With practices like block resleeving becoming more common, it's clear that consumers want more cubes; and perhaps more tellingly, high-strength aftermarket engine blocks have started to trickle onto the market (see "World at War," March 2006). Simply put, GM has stood on the brink of losing potential customers who feel the need for serious speed--particularly those who don't operate on race team bankroll.

Rest easy, power mongers: this spring, GM Performance Parts will release its revolutionary LSX Bowtie Block, a versatile, extreme-duty foundation that will also be surprisingly--if not downright shockingly--affordable.

"The goal with the LSX is to have a very feature-rich, high-end, race-capable LS family engine block," says Dr. Jamie Meyer, Product Integration Manager for GMPP. "But we also wanted to make sure that this block was within the grasp of just about any budget." You'll be pleased to hear the LSX Bowtie Block's projected MSRP will be around $2,500, with actual street prices likely in the neighborhood of $1,800 to $1,900. Compared to any other high-end block on the market--GM or otherwise--that's virtual pocket change. And what's truly astounding is the kind of value that comes along with this investment.

"We wanted a block that customers could really grow with," continues Meyer. "It's for this reason that we wanted as much rebuildability and compatibility as possible, and the LSX Bowtie Block offers across-the-board parts interchangeability. Thanks to this, a customer can build and rebuild an engine as his or her budget may allow--all without having to ever buy another block. With the strength we have built into the LSX, it has the structural character needed to withstand many years of use and abuse."Read on to get some insight into how this project came about at GM, as well as what makes this new Bowtie Block so special from a technical standpoint.

Behind the Scenes at GMPP
We spoke at great length to GM Performance Parts' Thomas Bates, a man whose title of Marketing Specialist deceivingly undervalues his position with the company and his role in the development of the LSX Bowtie Block. Basically, he's a product development specialist whose job is literally to bring good ideas to life--and to the market. "This LSX block wasn't originally my idea, it was that of the guy who was my boss at the time," states Bates. "He came to me and said, 'You know what would be really cool? An iron 6.0L block that you can bore the snot out of!' My response was, of course, extremely positive--and the next thing we knew, we had the really stout, killer piece of equipment you see here!"

Of course, a lot of design work transpired after the conception of this Bowtie Block, and Thomas was assigned a team of engineers to make the idea a reality. Trade-offs are inevitable when marketing folks and engineers come together to discuss what is dreamt of and the truth of what is actually possible. But what is so amazing about this project is how much of the original hopes came to fruition. "What we had typically done in the past when designing a block was to borrow production block tooling and modify it a little bit to get the cast we wanted. But with the LSX, there was no tooling to be had, because GM had destroyed it already," says Bates. "So we decided to make our own tooling, which is a big investment--but it just so happened that in doing so, it would enable us to make this new block all things to all people. That's pretty much how we went about designing most everything on this block: we opted to incorporate all of the features we needed from the get-go so that we didn't have to look back three years down the road and say, 'Oh jeez, that would have been nice!'"

Not the least of these features is the LSX's massive bore size. When talking about the project early on, Bates' team discussed certain parameters that they wanted to try and meet if at all possible, and one of the main ones was a 4.25 bore. "Granted, this would only be for a naturally aspirated application--but being able to accommodate this bore size would go a long way toward making competitive aftermarket blocks pale in comparison," says Bates. "It's one of the specific reasons we decided to do an iron block: to have the ability to go quite large, and--unlike with techniques like resleeving--still have a lot of strength left. That said, it was up to the engineers to figure out exactly how to accommodate this, and I'm happy to say we were able to do it."

That's no misprint: 4 1/4 inches! Thanks in part to the LSX's Siamese bores, this gaping diameter still leaves a 0.200 minimum wall thickness and is a full 1/8 inch larger than anything else out there. Combine this with the recommended max crank stroke of the same value, and you've got yourself over 482 cubes. As if this weren't enough, a tall deck version of this block will be available soon after the standard deck model's release. Its 9.700-inch height (nearly 1/2 inch taller than the standard deck model) will accommodate a crank with massive 4.500-inch throws, which translates to cubic inch displacements of well over 500 ci! But feel free to build as small as you like, too, as the blocks will be shipped with a ready-to-hone 3.990 bore.


0702gm_01_z Lsx 1/13

We had the opportunity to view a full-size mock-up of the upcoming LSX block during a trip to GMPP's headquarters--a model that's 100 percent accurate to the finished product save for it being made out of translucent, laser-hardened resin. Though a lot of the features are difficult to see in photos, the model helps visualize some of the internal structure changes of the LSX over production blocks. Real blocks will be made out of high-tensile-strength cast iron and will also be 100 percent CNC-machined.

0702gm_02_z Lsx 2/13

The first engine to be put together using a preproduction LSX Bowtie Block was a 454-inch mill assembled at Warren Johnson Enterprises. With prototype LSX heads and 640 hp, this engine is shown awaiting installation into the Reggie Jackson 1969 Camaro featured at this year's SEMA show. (Apologies for the carburetor, a very non-GMHTP item.)

0702gm_03_z Lsx 3/13

This slide provided by GMPP shows many of the outstanding features of the LSX--and they're not just race-specific. Beyond power-oriented items like six head bolts per cylinder and Siamese bores, the LSX retains all OEM exterior mounting features for all accessories and even incorporates an additional transmission bolt hole to better comply with the rules of drag racing sanctioning bodies.

0702gm_04_z Lsx 4/13

Up top, a thicker deck surface adds to head gasket retention even when using standard 11mm bolts or studs. Beyond this, the LSX block can be machined for up to half-inch head studs and also allows for use of a six-bolt head bolt pattern for applications with truly sick cylinder pressures. Down at the bottom, LS7 billet steel main caps are included and use 10mm fasteners; but if this isn't enough, the block can be drilled for use of larger studs. Large LS7 bay-to-bay breathing windows are used for reduced parasitic pumping losses. Says GMPP's Thomas Bates, "Finite Element Analysis was performed to determine where all the stresses were in the block, and what we found was that in the area where these windows are placed, there is no stress to begin with. All of the stresses pull on the middle of the block and around the outside of the block, which is where the main caps are tied in."