OVERVIEW
Model year 2001 marks the debut of a new, highly refined big-block V8. Introduced in GMC Sierra heavy-duty pickups and Medium Duty trucks, the L18 Vortec 8100 is the legendary GM big block for a new millennium, with a 33 percent increase in expected useful life and horsepower and torque that surpass the competition.

NEW OR CHANGED FOR 2001 MODEL YEAR

Revised Engine Block New Pistons with 5-Millimeter Top Land and Improved Firing Order Internally Balanced Crankshaft Replicated-Port Cylinder Heads Low-Noise, High-Durability Valvetrain Cast Stainless Exhaust Manifold Lost-Foam Cast Aluminum Intake Manifold Internal Positive Crankcase Ventilation (PCV) Modified Sequential Fuel Injection Electronic Throttle Control (ETC) Coil-Near-Plug Ignition More Durable Water Pump Improved Cooling System with Coolant Loss Protection Dual-Belt Accessory Drive Oil-Life Monitor and Level Sensors Raised Rocker Cover Rails Improved Sealing PUP Converters and Air Injection Reaction for California Thermoplastic Sight Shield Cast Aluminum Oil Pan All Metric Fasteners

CUSTOMER BENEFITS

BIG BLOCK
The Vortec 8100 is essentially a new engine; nearly 80 percent of its parts have been completely redesigned. Yet its foundation is one of the most celebrated engine components in automotive history: the General Motors big block.

The process of refining the Vortec 8100 engine block was similar to the one Powertrain engineers applied when they turned the small-block V8 into the Gen III LS1. The latest math-based engineering tools were used to improve the flow and distribution of oil and coolant, to refine castings and to improve production quality and efficiency.

The Vortec 8100 block shares its valve and bore centers, as well as its bore diameter, with the 2000 Vortec 7400 (L29). Yet stroke has been increased 9.4 mm (.37 in.) to increase displacement 700 cc and, most importantly, to deliver more horsepower and torque.

The main bearing caps have four bolts. This heavy-duty feature increases overall rigidity, and it further reduces noise and vibration. The bearings are manufactured with a new alloy called A260, which eliminates cadmium, a metal that has been deemed hazardous to the environment, and extends anticipated bearing life.

BETTER PISTONS
The Vortec 8100's pistons are more compact, with a shorter combustion height (the distance between the top of the piston and the wrist pin) and a tighter ring pack. The new design allows the increase in stroke without a significant increase in engine deck height, while still leaving sufficient clearance for the greater rotational diameter of the new internally balanced crankshaft.

The pistons and piston pin bores are teflon coated. Further, the pistons' shorter combustion height and skirt limit heat build-up underneath the piston during the combustion process, helping to ensure long engine life.

A short, 5-millimeter top land and new full-radius top ring improve combustion efficiency and decrease exhaust emissions. When fuel in the combustion chamber ignites, it burns from the center of the piston top outward. Any remaining unburned fuel mixture can be trapped between the piston and cylinder wall, above the top piston ring. Less depth from the top of the piston to the first ring leaves less space to trap air/fuel mixture, so the fuel burns more completely.

Finally, using math-based engineering tools, Powertrain engineers revised the Vortec 8100's cylinder firing order compared to the 7400. The new firing order (1-8-7-2-6-5-4-3) optimally balances the force exerted on the crankshaft during combustion, reducing wear on the main bearings and stress on the crank by seven percent.

NEW CRANKSHAFT
Vortec 8100s for trucks have a nodular cast iron crankshaft. The crankshaft is internally balanced and counterweighted. That moves counterweight mass from its typical position on the flywheel inside the crankcase, reducing bearing loads and stress on the crankshaft. The eight counterweights were aerodynamically designed to limit drag on the crank and increase horsepower. The crank dampener is mounted with a new elastic material called Vamac, which provides more dampening capability and longer life than conventional rubber. The dampener optimizes torsional and bending frequencies in the crank, and further reduces journal stress and vibration.

MORE EFFICIENT HEADS
The key design feature in the Vortec 8100 cylinder heads is replicated ports. Each intake port is now precisely equal in diameter and length. That ensures equal distribution of the air/fuel mixture to each cylinder, and limits variations in the torque produced by each. The results are a smoother engine, more efficient fuel management and lower emissions. The heads are designed for a balance of low ownership cost and maximum durability. Intake valve guides and seats are machined into the casting. The exhaust valves, which operate at much higher temperatures and are more prone to wear, have durable pressed-in cast iron guides and powder-metal seats. A new 18-bolt attachment pattern essentially circles each cylinder with six head bolts. The pattern optimizes the benefits of the replicated ports and improves gasket seal. A thicker, 1.3 mm head gasket (see BETTER SEALS) improves sealing and extends anticipated useful life.

QUIET VALVE OPERATION
In GMC Sierras and Yukon XLs, the Vortec 8100's steel cam has a maximum lift of 12 mm and duration of 209 crankshaft degrees for intake valves, 204 degrees for exhaust valves. Stiffer steel rocker arms and ball pivots are mounted on stiffer studs to reduce noise and extend engine life. The cam sprocket is enclosed with a cast-iron cover to further limit noise radiating from the valvetrain.

STAINLESS STEEL EXHAUST MANIFOLDS
The exhaust manifolds are cast from stainless steel, which are more heat-resistant and have a longer anticipated life than conventional cast iron. Each manifold is covered with a heat shield made of two layers of aluminized stainless steel. The shields keep heat from spreading into the engine bay and muffle the noise of exhaust gas flowing at high velocity through the manifolds.

MANIFOLD
Functional improvements in the intake manifold start with equal-length intake runners, which allow more even air delivery to all cylinders. The runners contribute to a broad, even torque curve with good engine breathing at higher rpm, and they directly feed the center of each intake port. The result is precisely equal air delivery to all cylinders and a smooth, even engine tone.

The Vortec 8100's aluminum intake manifold is lighter than conventional cast iron and reduces overall engine mass. It is manufactured with the lost foam foundry process, which delivers a number of benefits for the engine and the environment. Lost foam casting is essentially the reverse of conventional casting, which starts with molds and sand to fill the voids in the part being cast. Lost foam casting begins with a Styrofoam assembly, or a replica of the part being cast. Sand is poured around the assembly and shaken into its voids. Molten aluminum is then poured through the sand; the hot metal melts the foam, displaces it and cools in the shape of the part.

Lost foam can require less aluminum to cast a part of the same strength, meaning less weight and lower material costs. The process also allows more exact dimensional control. Machining is reduced 10 percent or more, and lost foam casting carries considerable environmental benefits. The sand used in conventional casting requires a binding agent to hold its shape inside the casting mold, and can't be recycled. The sand used in lost foam casting requires no binder and can be used over and over. There's a substantial reduction in raw material used and disposed. The primary byproduct of lost foam casting is melted foam, which largely evaporates as a non-toxic gas.

INTERNAL PCV
The lost foam process allows crankcase ventilation passages to be cast into the intake manifold. Orifices connect directly to the block. This feature eliminates the crankcase ventilation valve and external plumbing, which in turn reduces the number of parts, decreases maintenance requirements and removes potential leak sources.

SFI
The Vortec 8100 uses an improved version of Powertrain's patented Sequential Fuel Injection. SFI is one of the most precise fuel-delivery systems available, and it is a key contributor to the 8100's balance of good power and clean operation. The injectors aim fuel directly at the intake valves for good atomization and efficient combustion. High fuel pressure, at 400 kPa, means smooth operation in all weather and quick starts in even the hottest operating temperatures.

LOST FOAM INTAKE HIGH-TECH ETC
Before the Vortec 8100, Electronic Throttle Control (ETC) was largely reserved for premium, passenger car engines. There is no mechanical link between the accelerator pedal and the throttle. A potentiometer at the pedal measures pedal angle and sends a signal to the Powertrain Control Module (PCM); the PCM then directs an electric motor to open the throttle appropriately.

ETC delivers a number of benefits to the customer. Besides throttle pedal angle, the PCM measures other data, including the transmission's shift points, in determining how far to open the throttle. ETC delivers outstanding throttle response and greater reliability than a mechanical connection, which typically has a cable that requires adjustment and eventual replacement. Cruise control electronics are integrated in the throttle, further improving reliability and simplifying engine assembly.

The throttle body has been moved to the front of the intake manifold, where it delivers air to the intake runners most efficiently. The ortec 8100 is equipped with Delphi's high-volume version 1.2 Mass Air Flow (MAF) sensor, with integral inlet air temperature ensor. This MAF allows the PCM to adjust for optimal erformance at a given air temperature.

COIL-NEAR-PLUG
Redesign of the ignition system began with coil-near-plug park delivery. In place of a high-voltage switch that distributes spark to each cylinder from one or two coils, the Vortec 8100 has one coil for each cylinder, mounted on the rocker cover above each spark plug. Coil-near-plug delivers 50 percent more spark energy than conventional systems, contributing to smoother engine operation and reduced emissions. The rocker covers for each cylinder head are identical, for more efficient engine assembly.

With coil-near-plug ignition, the reluctor ring has been moved from the front of the crankshaft to the rear. The ring is a key component of Magnetic Reluctance (MR) or "mirror image'' ignition timing. MR is the most sophisticated timing system available, and it is more accurate than other methods in measuring the precise crank angle. It allows the Powertrain Control Module (PCM) to push spark timing to the limit of efficiency without detonation or engine knocking.

All applications are equipped with platinum-tip spark plugs. Extended plug tips drop the electrode further into the combustion chamber and closer to the center of the air/fuel charge. This allows more progressive combustion at lower rpm and smooths engine operation, particularly at idle.

WATER PUMP
The water pump has a durable cast-iron case and lightweight aluminum components, with a longer-life silicon-carbide seal around the shaft. The dual-delivery pump design moves an equal amount of coolant to both banks of the engine block. While the overall coolant flow rate is the same as that Vortec 7400, the 8100's water jackets have been redesigned to eliminate flow restrictions, increasing cooling efficiency.

MAXIMUM COOL
The complete cooling system, which includes a new surge tank rather than a recovery bottle, is pressurized. Full pressure greatly reduces the possibility of the coolant filling with air bubbles, and it helps maintain maximum cooling capability.

The radiator is 100 mm wider than that used with the 2000 Vortec 7400, with two liters more coolant capacity. The transmission cooler has been moved from in front of the radiator to below it, increasing airflow through the radiator and improving air-to-water cooling efficiency.

The system features subtle refinements not expected in a heavy-duty truck engine, including a modulated fan clutch that engages the cooling fan progressively, rather than with a sudden lurch. Even connections were carefully evaluated to improve performance.

Fitting beads and hose ends were designed for a tighter, more reliable fit. Clamps were specified for optimum pressure, error-free alignment and easy installation.

Finally, for some applications the Vortec 8100 has built-in coolant- loss protection. Even if the engine is completely drained of coolant, it can continue to operate at a reduced speed for a limited time so the operator can safely seek service. The PCM limits power and allows the Vortec 8100 to operate as an air/oil-cooled engine.

TWO BELTS
In their effort to minimize noise and vibration, Powertrain engineers designed the accessory drive system with two belts. For the pickup, one belt operates only the air conditioner-typically the noisiest engine accessory. With separate drive, the compressor can be mounted on the lower right of the engine, further from the vehicle cabin. The two-belt configuration decreases accessory drive noise seven decibels, or nearly 50 percent, at 1000 rpm. Further, it reduces side loads on the accessory pulleys as much as 50 percent, improving accessory efficiency and extending anticipated life. And thanks to a clever crank pulley design, the finished Vortec 8100 for Sierra and Yukon XL is actually 27 mm shorter than the Vortec 7400, with its single-belt accessory drive.

Cast-iron accessory brackets have been stiffened to further reduce engine vibration. The drive belts use a new non-neoprene compound that extends anticipated life to 150,000 miles.

SIMPLE MAINTENANCE
Oil changes are the only maintenance recommended for Vortec 8100 equipped full size trucks over the first 100,000 miles of operation, and even the oil changes are made as simple and efficient as possible. The Powertrain Control Module records engine temperature and length of operation at a given temperature, then indicates an oil change when it's actually needed, rather than according to a predetermined schedule. An oil-level sensor means even more convenience for the customer. The sensor indicates low oil levels when there's a loss of oil in the crankcase.

RAISED ROCKER RAILS
The cylinder head rocker cover mounting surface has been raised to improve sealing and extend the rocker-cover gasket's useful life. In essence, there is more metal and a thicker casting in the cylinder head and less in the rocker. The rail design prevents oil from collecting where it contacts the gasket when the Vortec 8100 is not running. Protecting the gaskets from oil slows their saturation and extends their operational life.

BETTER SEALS
Virtually every potential leak point was examined and sealed more effectively. The oil pan, rocker covers and intake manifold now have controlled-compression gaskets.

Nearly all engine components that are bolted together have metal tabs or studs that keep gaskets from compressing too tightly, maintaining maximum seal with longer gasket life. Combined with the 18-bolt cylinder head attachment pattern, new multi-layer graphite head gaskets ensure maximum seal over the anticipated life of the engine.

PUPS AND AIR
Vortec 8100s built for Sierra and Yukon XL sold in California are equipped with Air Injection Reaction (AIR) and pup catalytic converters. The pup converters are mounted upstream from the primary catalytic converters; they heat more quickly and reach emission light-off temperature before the primary converters. Exhaust-port-injected AIR further speeds light-off by injecting hot, fresh air into the combustion process, creating an exothermic reaction that heats the catalyst more quickly. PUPs and AIR are required to meet California's more stringent vehicle emissions standards.

BETTER LOOKS
A thermoplastic sight shield, or beauty cover, is fitted over the intake manifold between the cylinder banks. The shield immediately identifies one of the most powerful gasoline-powered pickup engines in the market, and it gives the Vortec 8100 the appearance of the thoroughly modern engine that it is.

LEADERSHIP
The new Vortec 8100 will be offered in Sierras and Yukon XLs for model year 2001. The Sierra also gets all-new five-speed automatic and six-speed manual transmissions. Yet GM's leadership in "big-block" V8 technology dates to at least 1958, when the Vortec 8100's progenitor was launched, with 348 cubic inches of displacement in the 1958 Chevrolet Impala.

In 1973, the 454-cubic-inch truck big-block was launched. It was retooled in the 1991 as the Mark V-a truly powerful pickup engine that met stringent 1990s emission requirements. The new Vortec 8100 bears little resemblance to those engines , beyond its bore centers and bore diameters. Yet it maintains a tradition of outstanding durability and class-leading power.

After extensive analysis of competitors' engines, the 8100 development team set a goal of 200,000 miles of useful life without major repairs-and then achieved it. The L18 has been tested and validated to meet this 200,000-mile durability standard. Extensive marine application, in which engines are often run wide-open for hours on end, fueled the durability improvements.

Yet durability is only one component of success in the heavy-duty pickup market. Another is outstanding power, and measured by both horsepower and torque, the Vortec 8100 beats the competition. Ford's 6.8-liter V10 produces 310 peak horsepower and 425 lb-ft of torque in its most powerful application, according to figures published for model year 2000. Dodge's 8.0-liter V10 makes 310 horsepower and 450 lb-ft of torque. The Vortec 8100 tops both with 340 hp at 4200 rpm and 455 lb-ft at 3200 rpm.

And it does so with better specific fuel consumption than the 2000 Vortec 7400. Thanks to improved ignition, more precisely monitored fuel injection and increased volumetric efficiency, specific fuel consumption (per liter of displacement) has improved four percent.

At the bottom line, the Vortec 8100 gives heavy duty Sierras class-leading engine performance. "With the introduction of the L18 we will be ahead of the competition, which happens to be a couple of V10s.

We have more displacement, and that's consistent with the needs of the commercial market, but our specific fuel consumption is actually better. We also believe we have a cost advantage." "We're quite pleased. The goal was 340 horsepower with 200,000-mile durability, but the battle cry was really `high-torque forever!' We're going to have the highest torque [gasoline] engine in the market, with the low-end pull commercial users want, and we've improved the breathing for high-end horsepower as well. We have them beat just about everywhere." --Terry Imig, Model Year Manager, L18 V8.