The following is an excerpt from WARD'S AUTO WORLD, January 1998:

OVERVIEW
The small block legend continues in model year 2001 with more horsepower and a host of refinements, including several engineered for the new LS6 V8. Yet the bottom line hasn't changed. The LS1 takes a back seat to no V8 engine, and remains one of the best bargains in the automotive world.


NEW OR CHANGED FOR 2001 MODEL YEAR


Camshaft from LQ4 6.0-liter V8 (Vortec 6000) Truck Engine

Eliminate Exhaust Gas Recirculation (EGR)

Increased Volume Fuel Injectors

Increased Flow Air Cleaner with Larger Mass Air Flow sensor (MAF)

Pup Catalytic Converters

Cast Exhaust Manifolds with New Gasket

Reduced Tolerance Main Bearings

Revised Oil Level Tube and Indicator

Extended Maximum Oil Change Interval

Two-point Water Pump Vapor Vent

Sleeveless Coolant Sensor

Revised Powertrain Control Module Calibrations

Revised Rocker Cover Castings


CUSTOMER BENEFITS

LQ4 CAMSHAFT
Powertrain engineers found an elegant, cost-effective answer when the platform team asked for a five-horsepower increase in the 2001 LS1: They borrowed a billet-steel camshaft from the LQ4 Vortec 6000 truck engine. The new cam has more advance and different timing, delivering more torque lower in the rev range. Coupled with an improved air cleaner developed for the LS6 V8, the new cam increase horsepower by five in the Firebird.

EGR ELIMINATED
Application of the LQ4 cam produced a valuable side benefit: elimination of the Exhaust Gas Recirculation (EGR) system. The new cam creates more valve overlap, or periods when both intake and exhaust valves are partially open at the same time. Increased overlap allows the LS1 to meet National Low Emissions Vehicle (NLEV) certification without EGR. Removal of EGR reduces engine plumbing and potential leak sources.

INCREASED VOLUME INJECTORS
New fuel injectors increase maximum fuel delivery to 3.55 grams/second. The injectors were developed specifically for the new Corvette LS6 V8, but have been applied to the LS1 as well. Shared injectors mean assembly efficiencies, and open the LS1 to further power increases in the future.

MAF SENSOR
The LS1 benefits from other improvements developed primarily for the LS6, including Delphi's high-volume version 1.2 Mass Air Flow sensor, with integral inlet air temperature sensor. This MAF sensor increases intake volume and allows the Powertrain Control Module to adjust for optimal performance at a given air temperature.

PUP CATALYTIC CONVERTERS
Firebirds equipped with the LS1 borrow a page from the Corvette by adding a pair of pup converters for model year 2001. Mounted upstream from the primary catalytic converters, the pups heat more quickly and reach emissions light-off temperature before the primary converters. The pups help all 2001 LS1s meet Low Emissions Vehicle (LEV) requirements.

CAST EXHAUST MANIFOLDS
Pup converters also allow the LS1 to be fitted with cast iron exhaust manifolds developed for the LS6. These manifolds increase exhaust flow slightly and reduce cost considerably. They are also more durable than the dual-wall stainless manifolds on the 2000 LS1. Other things equal, cast manifolds take longer to reach full operating temperature than stainless, but with the pup catalysts light-off is still achieved in less than 20 seconds. A new gasket allows the manifolds to be used interchangeably between the LS1 and LS6.

BEARING TOLERANCE
Reduced tolerances in the crankshaft main bearings mean a more precise fit. The result is an increase in long-term durability and, just as importantly, a reduction in something known to engineers as "cold knock"--a slight slapping noise from the engine before it reaches full operating temperature.

EXTENDED OIL-CHANGE INTERVAL
New computer algorithms extend the oil-change interval. The Powertrain Control Module records engine temperature and length of operation at a given temperature; with new data on real-world customer use, engineers have adjusted the software to allow longer intervals before an oil change is indicated. The LS1 has a maximum permissible interval of 10,000 miles with recommended conventional lubricant.

TWO-POINT VAPOR VENT
The number of water pump vapor vents has been reduced from four to two, reducing cost. Experience with the LS1 has shown that two vents are sufficient to help maintain proper pressure and control coolant aeration.

SLEEVELESS COOLANT SENSOR
The coolant temperature sensor, supplied by Packard Electric, uses a plastic insulator to protect electrical leads in the brass housing, rather than a rubber sleeve. The new sensor reduces the possibility of assembly rejection or shorting in operation.

PCM RECALIBRATION
With the hardware adjustments, the Powertrain Control Module has been recalibrated to maximize performance and efficiency and ensure certification to National Low Emission Vehicle (NLEV) standards.

NEW ROCKER COVERS
Rocker covers have revised bosses, allowing the covers to be used interchangeably between car and truck small-block engines and enhancing assembly efficiency.

CONTINUING FEATURES
The LS1 achieved Low Emissions Vehicle (LEV) status in California for model year 2000, thanks to higher capacity catalysts on the Firebird and revisions that increased flow through the Air Injection Reaction (AIR) system in all applications. Cars equipped with LS1s were also fitted with On Road Vapor Recovery (ORVR) systems. The LS1 continues the grand tradition of one of the most important engines in automotive history--the original small block V8. While it shares its 4.4 inch bore centers with the first small block, the LS1 has introduced a host of advanced technologies to the overhead-cam V8, including all-aluminum construction, a thermoplastic intake manifold and drive-by-wire electronic throttle.

The LS1 retains its high-efficiency gerotor oil pump, which is driven off the front of the crankshaft. Benefits of the gerotor design include improved low temperature delivery and better performance, due to lower parasitic power loss.

"This engine obscures the line between overhead cams and overhead valves. There's no distinction anymore. The LS1 excels in reducing mass, package size and cost, with outstanding performance and NVH that's competitive with overhead-cam V8s. Doubters said we couldn't do everything--particularly meeting LEV—with overhead valves. We've proven them wrong." --John Juriga, Total Integration Engineer, LS1/LS6 V8

LEADERSHIP
The LS1 has wowed the business and enthusiast press, and found a spot on the WARD'S AUTO WORLD list of the 10 Best Engines in North America each year since its launch, because there is no arguing with results. This V8 exceeds customer expectations with outstanding overall performance at modest cost to both the customer and the corporation.

"Tire-trashing torque is what you want in a world-class sports/GT car, and the LS1 delivers--RIGHT NOW—when overhead cammers are still spooling up. That such torque and horsepower come with more refinement than one has a right to expect in nearly six liters of thumping V8 proves how effectively the old small block has been redesigned."