Cast-Iron LSX Block - Low Buck Brawler

Part 1
When introduced in 1997, the diminutive 346ci LS1 was the proverbial tip of the displacement iceberg. GM has since taken the LS1 architecture and developed a whole host of block and head designs for both assembly-line and aftermarket uses. For enthusiasts looking for max performance, the cast-iron LSX block can achieve more than 500 cubes in its tall-deck configuration.

Things really got interesting in 2006, when GM launched the 427ci LS7. Standard equipment on the 505hp Corvette Z06, the LS7 featured new high-flow, rectangular-port cylinder heads. A year later, the company adapted the rectangular-port design into a mainstream engine offering called the L92. Compared with previous "cathedral port" heads such as the LS2 (which flowed 260 cfm on the intake side and 180 cfm on the exhaust at 0.600 lift), the L92 head had tremendous flow (316/189 cfm) and excellent velocity. In fact, a version of the L92 head is currently used on the base Corvette's LS3 engine.

Not long after the L92 was introduced, enthusiasts started bolting the engine's heads and intake onto 6.0-liter (and larger) blocks and making LS7-killing power numbers. According to Jason Mangum of Texas Speed and Performance (TSP), "Whereas the most-popular stroker combinations were LS2-based 402s and 6.0-liter iron 408s, the market has shifted to the L92/LS3 aluminum 6.2-liter block and LS3 heads. This an excellent block for the street, as the casting incorporates numerous revisions to increase strength.

"In stock form, the engine has a 4.065 bore and a stroke of 3.622, which yields 376 cubic inches," he continues. "Due to the thickness of the cast-iron cylinder liners, the LS3 block can be bored and stroked to 418- or 427-inch configurations. With a set of our ported LS3 heads and an aggressive cam, we can achieve 650 hp with the 418 and more than 675 hp with the 427."

TSP offers LS3 engine packages in both of the aforementioned displacements, in short-block ($4,095) and long-block ($7,399) forms. Mangum and company will even sell you a turn-key engine complete with an intake, fuel-system components, and headers for a quite reasonable $9,607.74.

Over the next few pages, we'll follow a 418ci LS3 as it takes form at Sunset Racecraft in Lubbock, Texas. (Note: Sunset typically handles the machining and short-block work for TSP, then ships the combo to TSP headquarters in Wolfforth for final assembly. In the case of our test engine, however, the entire job was performed at Sunset, with help from TSP lead tech Joseph Potak.) In next month's issue, the finished product will be bolted to a dyno, and a number of camshaft and cylinder-head changes will be performed to reveal the true power potential of the engine. If you're looking for a durable and affordable alternative to an LS7, we think you'll find that this low-buck LS3 stroker could be just the thing.