High-Performance 418ci Stroker Engine - Low Buck Brawler

Testing Texas Speed's 418-Cube LS3

Randall D Allen Oct 21, 2009 0 Comment(s)
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Part 2
In last month's installment, Texas Speed and Performance (TSP) used a brand-new GM L92/LS3 block as the foundation to build a high-performance 418ci stroker engine. Sunset Racecraft in Lubbock, Texas, bored the block to 4.080 inches (4.065 is stock) and stuffed it full of such heavy-duty components as a custom Eagle 4.00-inch stroker crankshaft, Eagle connecting rods, and Diamond Racing pistons. TSP then completed the engine build with its own Texas Speed/Precision Race Components (PRC)-prepped cylinder heads and accessories.

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According to TSP co-owner Trevor Doelling, "The key to the power potential of this 418 lies in the blueprinted short-block and the extensive testing and development work that are done before it reaches the market. For enthusiasts with an LS engine with a bore of 4.00 or greater, the factory L92/LS3 head is an excellent choice, flowing almost 320 cfm in stock form. By developing a five-axis CNC porting program, we achieved a higher-flowing head-356 cfm at 0.650 lift-that improves upon the factory velocity and provides a much more balanced intake-to-exhaust flow ratio of 66.4 percent (vs. the stock 59.8 percent)."

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Dyno Results
With our 418 fully assembled and ready to rock, Sunset's techs strapped it down on the shop's Dynamic Test Systems, Inc. (DTS) model 4000G engine dyno for a series of pulls. The engine was tested in three different configurations: with stock heads and a mild Comp hydraulic roller cam, with the TSP/PRC heads and the same cam, and, finally, with the TSP/PRC heads and a more aggressive Comp grind.

Baseline numbers checked in at an outstanding 608 hp at 6,300 rpm and 561 lb-ft of torque at 5,200 rpm. Torque exceeded 500 lb-ft from 4,100 to 6,300 rpm, while average power and torque (measured from 4,000 to the 6,500-rpm redline) checked in at 531.5 and 532, respectively. It's clear that even in its least radical form, the TSP 418 is a serious performer across the rev range.

The addition of the ported PRC L92/LS3 heads paid real dividends, pushing the peak figures to 630 horses at 6,400 rpm and 570 lb-ft at 5,200 rpm. Power and torque improved across the rpm spectrum, with average gains of 12 and 11.5, respectively. The real story lies in the torque boost between 5,300 and 6,500, which ranged from 10 to 20 lb-ft.

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The final test involved swapping out the baseline Comp cam for a hotter stick and installing one of TSP's own 100mm MAFs. The end result was a towering 641.2 hp at 6,400 rpm and 578.5 lb-ft of torque at 5,200. Average hp and torque rose by 6.6 and 6.3, respectively, while the peak numbers jumped by 10.9 and 8.0. Although the peak and average gains were modest, the larger cam and higher-flowing MAF added both power and torque from 4,900 rpm all the way to the redline without sacrificing on the low end.

Conclusion
According to Doelling, "The redesign of the Gen IV block from the LS2 into the larger-bore L92/LS3 allowed builders to offer stroker engine packages of up to 427 cubic inches without resorting to expensive cylinder liners and machine work. It's now possible to sell a top-quality 418 or 427 short-block or long-block at a budget price. Since enthusiasts have their choice of cams, we can work with them to build L92/LS3 packages that offer anywhere from 500 to 675 hp, depending on their intended use.

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"For owners looking to make even more power, both engines are rated to take up to a 200hp shot of nitrous. Custom pistons are available to take the compression from 11.1:1 down to 8.5:1, allowing a forced-induction 418 to achieve over 1,000 hp. In fact, other than the camshaft and dished pistons, our twin-turbo street car-which makes 1,063 horses at the rear wheels-uses all the same components as this build. That shows just how robust and powerful the package is."

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