and torque from . Other important differences between the Vortec 8100 and older big-blocks include a changed firing order. The firing order of older big-block engines is 1-8-4-3-6-5-7-2 while Vortec 8100's firing order is 1-8-7-2-6-5-4-3. Other upgrades of Vortec 8100 include a new 18-bolt head bolt pattern, longer connecting rods, different symmetrical intake ports, different oil pan rails, and the use of metric threads throughout the engine. The fuel-injection system for the Vortec 8100 is nearly identical to that used on Gen III small block engines, right down to the fuel and spark tables in the ECU. Vortec 8100s were built at GM's Tonawanda Engine plant while the engine block and cylinder head were cast at Saginaw Metal Casting Operations. The last L18 was manufactured in December 2009. L18 Applications: GM sold the Vortec 8100 to Workhorse (now a division of Navistar), making it one of the most popular engine choices in gas powered Class A motorhomes during the first decade of this century. GM stopped installing big-block V8s in the Silverado HD trucks when the GMT-800 series was discontinued in 2007. Chevrolet/GMC C3500HD 2001-2002 Chevrolet Silverado/GMC Sierra 2500HD & 3500HD (option) Chevrolet Suburban/GMC Yukon XL 2500 (option) Chevrolet Express/GMC Savana 2500 & 3500 Chevrolet Avalanche 2500 (std on GMT800 2500) Chevrolet Kodiak/GMC TopKick Workhorse Class A motorhomes. T-98 Kombat armored vehicles. U-Haul's truck. Malibu Boats, e.g. Wakesetter. MasterCraft Boats Aftermarket Many custom engine builders across the United States, as well as a large variety of aftermarket components manufactured for the Big Block family, make it possible to build a complete Big Block engine that contains no Chevrolet components. Blocks made of both iron and aluminium alloys, for many different purposes—e.g. street-use, racing, etc.—are available in stock or modified configurations, as well as with increased deck height to allow for a longer stroke or more favorable rod length ratios, depending on intent, providing the ability to make engines with capacities of , , and as large as . See also From the 1950s through the 1970s, each GM division had its own V8 engine family. Many were shared with other divisions, but each design is most closely associated with its own division: Buick V8 engine Cadillac V8 engine Chevrolet Small-Block engine GMC V8 engine Oldsmobile V8 engine Pontiac V8 engine Holden V8 engine GM later standardized on the later generations of the Chevrolet design: GM LT engine—Generation II small-block GM