Scoggin-Dickey Parts Center (SDPC) Race Shop is known for building some high-horsepower engine combinations for race and street cars, and it's latest creation shows what you can do with GM's production cast-iron, L8T truck block, along with a host of other factory parts. It's no secret that enthusiasts and engine builders have regularly pushed the limits of stock LS and LT engine blocks well beyond their original design envelopes, and even Chevrolet Performance's race-oriented LSX block has been pushed beyond its limit as well. Enter the L8T enginea robust 6.6-liter engine built for heavy duty, full-size trucks. The biggest thing that we've contributed to the high-performance market are production pieces that can be used in that market, said SDPC Race Shop's Keith Wilson. We started looking at that engine when GM announced the 6.6 engine in the HD trucks, and we thought that might be our next 5.3 on steroids. It's a very heavy-duty, Siamese-bore block. Weight wise, it's pretty heavy, heavier than an LSX block, which is the only downside to it. We wanted to see how it would perform and what it could handle, and started in early 2021 on the project, Wilson told us of the project that was given the green light by SDPC's Fixed Operations Manager Nicky Fowler, and spearheaded by SDPC Race Shop's Kurt Urban and Aaron Shoaf. [gallery ids="24533,24534,24535,24536,24537,24538"] The L8T engine block was designed for GM's direct-injected, 6.6-liter gasoline powerplant for 2020-later GM trucks, and features 4.065-inch finished cylinder bores and a 9.240-inch deck height. With the production 3.86-inch stroke crankshaft, displacement checked in at 400 cubic inches. The L8T block is available as a production bare block for around $1,900 through SDPC. Part number SDR98759 gets you the SDPC Race Shop-modified L8T engine block with 6-bolt steel main caps, dowel locations to accommodate LS and LT, and the DOD towers machined out of the block. To complete the short-block, SDPC Race Shop utilizes GM's production HD forged-steel crankshaft that offers a 3.860-inch stroke and is equipped with a 58x crank reluctor wheel and 8-hole flywheel bolt pattern. From there, Callies Performance Products Ultra connecting rods and Wiseco 2618 forged aluminum pistons are installed with Total Seal piston rings. Going back to using more factory products, SDPC Race Shop utilized production bearings and gaskets to keep everything together. As this was a design and engineering exercise, the camshaft from Competition Cams is a proprietary one that works with factory 1.8:1-ratio rocker arms that have been upgraded with CHE trunnions. Moving onto the airflow part of the equation, SDPC Race Shop chose to use a set of LT4 cylinder heads, which come from the C7 ZO6, Camaro ZL1, and Cadillac CTS-V programs, all of which were designed from the start for forced induction applications. These aluminum cylinder heads retain the production GM LT4 valves; 2.130-inch Titanium valves on the intake side and 1.590-inch stainless steel valves on the exhaust side. SDPC Race Shop then modifies the heads to allow the use of an LT1-spec, Holley Hi-ram intake manifold and Holley 102mm throttle body. Providing the fuel is a set of Holley 220 lb/hr fuel injectors in a port-fuel-injection configuration, and a Holley Dominator EFI system runs the show.
Boosting the atmospheric pressure entering the engine starts with a pair of Hooker Blackheart LT cast exhaust manifolds that feed exhaust gases to a pair of Precision Turbo & Engine PT7685 turbochargers. The compressed air is then cooled by a Shearer Fabrications air-to-water intercooler, and Precision Turbo wastegates and blow-off valves manage the air pressure. The forced induction setup, oddly enough, is a proven combination that SDPC Race Shop's Kurt Urban already runs in his daily driver truck. Maxima Racing 15W-50 break-in oil was used to keep the engine lubricated and an ATI Performance Products Super Damper was employed to keep the rotating assembly turning smoothly. Final dyno pulls on the 9.5:1 compression ratio engine were performed using VP Racing Fuels MS 109 for most pulls up to 1,600-1,800, and then C16 was utilized on the maximum effort pulls, as the Race Shop had a limited supply of the high-test fuel at the time. During testing, it was discovered that the production, LT-based oil pump became a limiting factor in horsepower production. From the top-down, we were all pretty excited about the build. However, the oil pump wouldn't support the horsepower we thought it would make, Wilson explained. The stock oil pump falls off tremendously in pressure after 5,500 rpm and won't support much over 1,000 hp. We have two solutions; one we're testing that will be out to the public that can be used in a wet-sump application, but the quick solution was to modify a wet-sump pan for an external Peterson Fluid Systems pump. With that change, the Race Shop was able to turn things up, with the final numbers coming in at 2,077 horsepower and 1,785 lb-ft of torque at 32 psi of boost pressure. SDPC Race Shop plans to offer this engine in a number of configurations. In addition to the production bare- and short-block versions, customers can purchase the SDPC Race Shop-spec short-block or long-block, with the latter coming in at around $20,000 for the 2,000hp-capable engine. SDPC Race Shop will also offer turbochargers, wastegates, blow-off valves, Shearer Fabrication intercooler, and Hooker exhaust manifolds to customers as well. Fresh off the SDPC Race Shop dyno, the company's new engine will go on display at the 2021 SEMA and PRI trade shows, and interestingly enough, will likely be dropped into Kurt Urban's Malibu Wagon that he has built for open road racing competitions. The SDPC Race Shop continues to show enthusiasts just what is capable with stock GM parts. Over 2,000 horsepower from a production, cast-iron small-block Chevy engine the LSX/LT family of engines continues to impress! Source Scoggin-Dickey Parts Center Race Shop (806) 798-4159 www.sdparts.com