With the majority of the short-block assembled in Part I, the L92/LS3 engine is ready to be completed and then tested on the dyno. To recap the build, in Part I Texas Speed and Performance (TSP) used a brand-new GM 6.2L aluminum L92/LS3 block as the foundation to build a 418ci engine. TSP utilized the services of Sunset Racecraft in Lubbock, Texas, to bore the block to 4.080 inches (4.065-inch bore is stock) and then install a custom Eagle 4.00-inch stroker crankshaft, Eagle connecting rods, and Diamond Racing pistons. Texas Speed completed the buildup with its own Texas Speed/Precision Race Components (PRC)-prepped cylinder heads and accessories.
With the short-block completed,...
With the short-block completed, attention turns to the cylinder heads and valvetrain. New GM lifter trays are utilized along with GM LS7 hydraulic roller lifters. After lubricating the housing and roller portion of the lifter with assembly lube, they're pushed into the tray, all four trays are fitted into the block, and the single 10mm bolt that retains each one is torqued to specification. Although the Gen IV lifter trays are similar to the original Gen III design, the Gen IV's enhanced bay-to-bay breathing architecture necessitated a redesign.
According to Trevor Doelling, co-owner of TSP with Jason Mangum, "The key to the power potential of the 418 lies in a blueprinted short-block that has undergone extensive development and testing before it reaches the market. Working in conjunction with the manufacturers and Sunset Racecraft, we developed engine packages that offer value and performance. For enthusiasts with an LS engine with a bore of 4.00 or greater, the factory L92/LS3 head can be utilized and flows almost 320 cfm on the intake in stock form. By developing a five-axis CNC-porting program, we achieved a higher-flowing head that improves upon the factory velocity and provides a much more balanced intake-to-exhaust flow ratio," (66.4 percent vs. stock 59.8 percent).
Retailing at $4,095, the TSP short-block is offered in both 418 and 427ci versions (PN 25-418LS3LB or 25-427LS3LB) and is a solid foundation for a serious LS-series build. The long-block costs $7,399 (PN 25-418LS3LB or 25-427LS3LB). Follow along as we complete the assembly and dyno test the TSP 418.
Dyno Testing
All testing was completed on Sunset Racecraft's Dynamic Test Systems' (DTS) model 4000G dyno. HP Tuners VCM Suite was used to tune the computer, the timing was locked at 28 degrees, and the knock sensors were removed for testing.
VP 101-octane unleaded was utilized in the cell (TSP says 93-octane would work just as well), fed to the engine via the shop's Aeromotive fuel pump, and regulated to 58 psi. In order to ensure consistency in the test results, the various combinations were pulled after the engine had recorded 165 degrees on the test cells' DTS model S-1007M engine-cooling system. No engine-accessory belts were required since a Meziere electric water pump was utilized.
Once the engine reached temp, the dyno operator took it to 3,800 rpm and then applied a dyno load. Once loaded, the engine was slowly brought up to 3,000 rpm and pulled until the specified redline. Standardized SAE calculations were used to correct the horsepower and torque to industry standards.
The block is fitted with two...
The block is fitted with two new GM cylinder-head aligning dowels (PN 12570326) per bank, the block surface is wiped clean with acetone, and GM MLS LS7 head gaskets (PN 12610046; sold individually) with a bore size of 4.125 inches are placed over the dowel pins.
Dyno Test Configurations
Test No. 1 - (Baseline) - Stock L92/LS3 heads, P.T.M. 92mm throttle body, SLP 85mm MAF, stock L76/L92 intake, and Comp Cams hydraulic roller camshaft with 242/248 duration at 0.050 and 0.612/0.615 lift on a 114 LSA
Test No. 2 - Replaced stock L92/LS3 heads with PRC ported L92/LS3 heads
Test No. 3 - Swapped to a Comp Cams hydraulic roller camshaft with duration of 251/259 at 0.050 and 0.660/0.603 lift on a 111 LSA, replaced SLP 85mm MAF with TSP 100mm MAF
Results:
Baseline numbers for the 418 were an outstanding 608 hp at 6,300 rpm with 561 lb-ft of torque at 5,200 rpm. At the lowest recorded rpm of 4,000, the engine was already making 487 lb-ft of torque with 371 hp. Horsepower jumped over 500 at 4,800 rpm and crested the 600 mark at 5,900 rpm through the redline of 6,500. Most impressive was the torque, which exceeded 500 lb-ft from 4,100 to 6,300 rpm. Average horsepower and torque from 4,000 to 6,500 rpm checked in at 531.5 and 532 lb-ft, respectively.