GM LS1: Not The Same Old Song And Dance

GM LS1Sep. - Oct. 2002 Lane Racing And Rodding Article By Jim Kaekel, Jr.

The small block Chevrolet has been a formidable performer on the street and in racing since its introduction in 1955. Its enduring popularity is beyond argument. GM's newer small block, the Generation III LS1, has been drawing such rave reviews recently that it could wind up becoming the powerplant of choice for future racers and rodders. It's already the "spec" engine for the ASA (American Speed Association) and is catching on quickly in NHRA's and IHRA's popular Stock Eliminator classes as well. Ed Woodard, Technical Representative for Holley, believes that the LS1 will soon be the favorite engine for Chevrolet enthusiasts and says that many of the engines are already finding their way into race cars street rods and street machines. Sales of bolt-ons for the LS1, including cams, headers and other accessories are on the increase as well. The LS1 is also gaining in popularity as an "over the counter" crate engine, particularly for individuals who wish to update traditional muscle cars or street rods by replacing the original powerplant with a lightweight, powerful, sequential electronic fuel injected engine.

Many industry insiders initially scoffed at the LS1's traditional pushrod design at a time when overhead cam engines had become so popular, but Chevrolet felt that pushrod design engines were less costly to manufacture, package, and maintain than the OHC counterparts. Besides, GM designed the engine so other versions could eventually be manufactured for use in their popular truck lines.

Introduced in the 1997 C5 Corvette, the LS1 was designed with a "clean sheet of paper" approach and, therefore, has little in common with the traditional, earlier small block other than the same 4.40" bore center spacing. The LS1 uses a lightweight aluminum block, heads and oil pan, composite intake manifold, and a unique ignition in which the spark plugs are fired by a "coil-on-plug" system with individual coils for each cylinder. The system generates an intense spark and very accurate timing.

The LS1's alloy block, cast from 319 heat treated aluminum, weighs just 107 lbs. (53 lbs. lighter than Generation II blocks) and utilizes external stiffening ribs and six bolt steel main bearing caps to provide a rigid casting. Each block is fitted with centrifugally-cast gray iron cylinder liners that have a finished bore size of 3.897". When combined with a 3.662" stroke, displacement figures out to be 345.69 cubes, although the engine is still marketed by GM as a 5.7 liter or 350 cubic inch engine. The cylinder sleeves restrict substantial oversize boring, but the LS1's displacement can be increased with an aftermarket stroker crankshaft.

The nodular iron LS1 crankshaft incorporates large (2.100") rod journals and accepts the same rod bearings as traditional small blocks, but has a center thrust bearing location and an ignition trigger wheel that is an integral part of the casting. The connecting rods, made from powdered metal, employ a 9mm cap screw instead of a bolt and nut assembly which yields a simpler assembly and lower rotating mass. The LS1's cast aluminum pistons are lighter because they lack the steel struts common to earlier pistons and because they are for a smaller bore size. Pistons are fitted with 1.5mm compression rings with ring tension reduced by 30% compared to previous designs. Extra long head bolts, which thread deep into the block casting, reduce bore variations, according to GM engineers.

As with any performance engine, the cylinder heads are the true highlight of the LS1. Cylinder head guru Ron Sperry, a key player in the development of the original Chevrolet "bow tie" cylinder heads, was an important contributor to their development. The head's superior "straight shot" intake port design is possible because only four head bolts surround each cylinder, rather than the five headbolts used on earlier small blocks. Pushrod holes, head bolt and rocker arm mounting bosses were also carefully engineered so as to not adversely affect intake port location. The 200cc intake runners are large at the port opening and then taper down to promote air flow velocity and stability, while the unique 15° valve angle allows the short turn radius in the exhaust runners to be very efficient rather than a hindrance as it was on early small blocks. The heads are fitted with 2.00" intake and 1.55" exhaust valves, resulting in a head that flows dramatically better than previous designs.

In 1998, the engine made its debut on the drag strip in NHRA Stock Eliminator competition. Class rules allow the engines to be fully blueprinted and use open headers, but very few internal modifications are allowed. In spite of these limitations, several electronic fuel-injected, LS1-powered Firebirds and Camaros have run 1/4 mile E.T.'s as quick as 10.30 seconds with ready-to-race weights well over 3,000 lbs. Two-time NHRA Stock Eliminator world champion Al Corda has been racing a new LS1-powered Firebird and currently sits atop the NHRA national points standings. Past world champion drag racer Amy Faulk has also had a great deal of success behind the wheel of her LS1 Firebird stocker. Other than a few cracked blocks caused by excessive wheelstands, the engines have proven to be very reliable in drag race applications.

Beginning with the 2000 race season, the American Speed Association adapted the LS1 as their "spec" engine, replacing previous V-6 engines after building costs skyrocketed. ASA founder Rex Robbins worked with GM Raceshop to develop an engine program that would not only help the show, but increase competition and cut out dependence on the performance aftermarket. Referred to as the Vortec ASA 5700, the engines are modified versions of their stock counterparts. The engines are shipped directly from GM with a bigger camshaft, stiffer valve springs and lightweight retainers. Lingenfelter Engineering, which works as a technical partner with the ASA and GM, makes several other modifications to the powerplants including converting them to dry sump oiling. Lingenfelter also maintains the engines.

Could the LS1 be the small block Chevy of the future? Will LS1 manifolds, cylinder heads, camshafts and headers eventually take the place of all the small block Chevy parts hanging on the walls of today's speed shops? Maybe Ed Woodard has the most prophetic evidence of what that answer might be. According to him, Lunati's number one selling crankshaft today is not for early small block Chevys. It's for the Generation III LS1.

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