The GM Performance Parts LSX block has made quite an impression with LS-series enthusiasts world-wide. Its standard deck size of 9.26-inches and the LSX Tall Deck Block, which features a 9.70-inch deck height, allow builders to create 364 to more than 500 cubic inches of modern power. The siamese-bore design and provisions for six-bolts-per-cylinder heads, combined with a true, priority-main oiling system that can utilize either wet- or dry-sump oiling, means it's packed with features, and a value leader for enthusiasts to build extreme combinations.
Though the iron LSX block weighs in at 225 pounds, or roughly double the weight of the LS series aluminum blocks, the weight penalty is negligible for the racer who was previously using a 6.0-liter iron block as the basis for race applications.
Trevor Doelling of Texas Speed and Performance (TSP) states, "The LSX standard-deck block is used to build a wide variety of displacements that range from 364 to 454 cubic-inches, while the LSX tall-deck block is capable of engine builds of more than 500 cubic inches. With the LSX blocks, the smaller-bore variants such as the 408 or 427 are consumer favorites for power-adder combos, whereas the 440 and 454 cubic-inch variants are typically for naturally aspirated builds. Our most popular combinations are the 454 cubic-inch engine (4.200-inch bore by 4.10 stroke) and the 440 cubic-inch variant (4.125-inch bore by 4.10 stroke). LSX 454 pump-gas engines with stock LS7 heads and conservative cam specs routinely exceed 650 hp and 590 lb-ft of torque on the dyno.
"The power is made possible by GM's excellent LS7 heads which in stock form flow race-like numbers of 359 and 214 cubic feet per minute (cfm) on the intake and exhaust, respectively. Add more head flow with our ported LS7 heads and install a more aggressive camshaft and naturally aspirated 750-plus horsepower combinations are easily obtainable on a budget."
Follow along as we show the major components of an LSX 454 build. Then we'll head into the dyno room at Sunset Racecraft to find out how much power and torque the crate engine can generate, before swapping an MAF, heads, a camshaft, and an intake to make even more power.
An LSX block made from CNC-machined...
An LSX block made from CNC-machined cast-iron comes from GM with 3.990-inch bores that are ready to hone. To create a 454 cubic-inch engine, the block is first decked and then the bores are opened up to 4.185-inches on a Rottler F-67A, three-axis CNC machine by Sunset Racecraft.
Dyno Testing
Assembly And Configuration Changes
All short-block machining and assembly work was completed by experienced technicians at Sunset Racecraft in Lubbock, Texas. Once the short-block is completed, it is normally transported across town to Texas Speed where the ancillary short- and long-block assembly and order fulfillment occurs. Since Sunset Racecraft is equipped with a Dynamic Test Systems, Inc. (DTS) model 4000G engine dyno, Texas Speed performed its portion of the labor at Sunset Racecraft, along with all configuration changes of the LSX454 while in the dyno cell.
Dyno Test Procedures
HP Tuners VCM Suite was used to tune the LS7 computer that utilized a Superior Wiring Harness for testing. Each configuration shown in a dyno graph was "tuned" to optimize the specific combination on the dyno. No LS-series knock sensors were employed in the testing, as all dyno runs were recorded and analyzed with HP Tuners before additional changes were made to optimize the combination. In general, timing was locked at 28-degrees and the targeted air-fuel ratio was 12.8-13.0.
Though a specific component achieved a dyno recorded gain, it should be noted that the object of the testing was not to document a specific component, but rather to systematically increase the amount of air flowing through the engine to allow it to produce more power and torque. The test order for each component provides an empirical data point as to how the component itself will perform, but changing the order of the component testing would most certainly change the individual results.