2,000+ HP Capable 416 cid LT Engine

Specializing in building LS and LT engines, Late Model Engines, LME, in Houston has been on the cutting edge of the GM late model market for a number of years. In fact, the shop took home our America's Best Engine Shops honor for 2020 in the race category. We recently caught up with the guys at LME and they had just finished up work on a newly released combination expected to take the GM late model LT market by storm. The build consists of a 416 cubic inch Iron Block LT engine, capable of making 2,000 horsepower in a forced induction application. And it's our Engine of the Week. Hey everyone, I'm Jackie Van Ham for Engine Builder and today I'm walking you through the details of Late Model Engines' newest 416 cubic inch Iron Block LT engine, a combination becoming extremely popular for high horsepower in the latest model GM vehicles. The foundation for the build comes in the form of a GM 6.6 Liter Production Iron Block, typically found in 2020 and newer Model Year Silverado HD and Sierra HD trucks with the gas engine option. The GM 6.6 Iron Block shares many similar traits with the 6.2 Aluminum version found in newer Camaros, Silverado 1500s, Cadillac CTSVs and Corvettes, making it a direct swap for the factory aluminum units. The Iron Block pertains all of the great characteristics from the Aluminum 6.2, such as oil squirters paired with larger head fasteners than their LS counterparts, but also adding some updated features as well. The most important of these updated features in the Iron Block is the cylinder wall thickness. Believe it or not, the Iron 6.6 Liter Block has the exact same cylinder wall thickness as an aftermarket GM LSX Block. This allows builders to go all the way up to a 4200 bore size in a naturally aspirated combination. In a forced induction application, LME feels extremely comfortable with a 4125 bore size. For this particular 2000 horsepower build, however, LME decided to go with a 4070 bore size in order to add even more cylinder wall thickness to make the combination ultra-reliable. Another upgrade found on the Iron 6.6 Block over the Aluminum 6.2 Liter is the extra struts on the deck surface around the head bolt locations. The 6.6 features these additional struts on the deck surface, reducing distortion and allowing the cylinders to remain straight and round at higher cylinder pressure levels. The cylinder bores in the Iron version are also upgraded in length, allowing for greater piston stability by keeping more of the piston up inside the cylinder at bottom dead center. Moving on to the rotating assembly, LME was tasked with choosing components that would reliably meet the 2000 horsepower goal. For the crankshaft, LME chose to use a 4 inch stroke crankshaft for an LT dry sump configuration, providing output of 416 cubic inches. This crankshaft features a long post snout for a dry sump application as well as an 8 bolt flange utilizing factory LT flywheel and flex plate combinations. The crank also features center counterweights for enhanced bearing load distribution, allowing it to withstand both high boost and high RPM. For conrods, LME is using steel 6 125 inch I-beam rods that are rated to withstand 2400 horsepower and feature L19 fasteners. Rounding out the rotating assembly is a set of diamond forged pistons produced exclusively for LME. The piston is a 9 pocket forged piston with additional strutting to support the wrist pin boss area, making it a very sturdy design. The pistons utilize a trend performance wrist pin and also feature lateral gas ports and a 16cc dish top, resulting in a 10.5 to 1 compression ratio when paired with the LME Edelbrock casting cylinder head. For camshaft selection, LME chose one of their custom hydraulic roller cams, ground specifically for high output and high RPM forced induction applications. Technology available today allows for aggressive hydraulic roller lobe profiles that will make big power and turn high RPM while requiring virtually no maintenance. On many of these newer vehicles, it can be extremely difficult to access the rocker arms when the engine is installed in the vehicle in order to check lash on a solid roller, so utilizing a more popular hydraulic grind makes sense in this application. Paired with this custom camshaft is an LME billet VVT delete front cover and timing gear setup. This kit is available in both dry sump and wet sump configurations. The kit utilizes a one-piece upper cam gear with a custom located camshaft dowel pin, eliminating the bulky factory multi-piece upper. The LME kit works with factory camshaft dowel pin locations and is therefore compatible with any standard LT camshaft. When it came time to choose the induction package for this combination, there was no doubt for LME what components would be chosen. This engine features the new-to-market LME Edelbrock casting cylinder heads. This raw head casting allows LME to start with a blank canvas and provides complete control and optimization of the valvetrain layout as well as custom port locations for maximum performance. The raw casting also features a much thicker deck surface to hold this additional power and features provisions for 6-bolt block cylinder head fastener layouts in the future. The LME cylinder head features larger than OEM valve sizes in conjunction with a one-of-a-kind intake and exhaust port location, resulting in flow bench numbers exceeding 400 CFM on the intake port and 310 CFM on the exhaust port. Additionally, LME chose to use a Manton rocker arm, designed to be used on a factory-style cylinder head. These Manton rocker arms, paired with a set of Manton pushrods and Johnson short-travel lifters provide this build with a reliable, maintenance-free 8,000 RPM valvetrain for the 2,000-horsepower capable build. This induction package, when topped off with either an LME Billet LT intake manifold or a Whipple-style supercharger, is a proven package, providing quality performance in the LT aftermarket industry. Well, that does it for this episode of Engine of the Week. Thanks to our sponsors, Pengrade One, SCAT Crankshafts, and L-Ring. Please like, comment, click like and share and subscribe if you haven't already. And if you have an engine you'd like to see featured, please email our editor, Greg Jones at gjones at babcox.com. We'll see you next time.