4.8 Vortec Chevy LR4 Engine

Being very alike from a mechanical point of view, GM’s LS motors and Vortec ones, built on their framework, were employed for almost every brand of the company, comprising Chevrolet, Pontiac, Buick, GMC, Cadillac, Saab, Izuzu and Hummer.

As both LS and Vortec motors are pretty widespread, they are treated as contemporary motors of high efficiency. Having fantastic output, these motors can be susceptible to various modifications, including turbo and superchargers, high-flow cylinder heads, intake systems, camshafts plus nitrous oxide. Besides, many aftermarket details are in stock for sale for LS swap motors. Crate engines are obtainable and you are free to get an old motor pretty cheap at the junk yard.

Summit Racing has made some guidelines for each motor of the series for engineers, tuners and just car enthusiasts to have a better idea of peculiarities of LS motors.

Key Facts:

  • Keeping manual transmission, LR4 motors, released between 1999 and 2000, featured crankshaft with a rear flange of 1.250 inches. (Casting #12553312)
    The further versions were equipped with a crankshaft with a rear flange of 0.857 inches. (Casting #12553482)
  • In 2001, LR4 plus LM7 motors gained MLS gaskets.
  • LR4 and LM7 motors, released between 1999 and 2003, kept return-type fuel injection systems.
  • In 2004, motors turned returnless (Express is the only exception).
  • GM/ Chevrolet LR4 is a 4.8-liter (293 cu in) natural aspirated V8 90 degree 4-cycle gasoline motor, pertaining to the Gen III small block V8 truck engine lineup.
  • Being often called Vortec 4800 and serving as a substitute for GM’s L30 with 5.0-liter displacement, this motor was manufactured at St. Catharines, Ontario and Romulus, Michigan, in 1999-2006.
  • Keeping V8 90 degree cast iron cylinder block with five-bearings crankshaft, 2 aluminum heads, one-piece cast camshaft plus 2 valves per cylinder, LR4 featured a sequential multi-port fuel injection system plus a throttle body of 78 mm (3.07 inches). Moreover, it gained Coil-Near-Plugs ignition system.
  • Featuring Cylinder bore of 96 mm (3.78 inches) and piston stroke of 83 mm (3.27 inches), its compression index equals to 9.4. The output is 255 hp (258 PS or 190 kW) – 285 hp (290 PS or 213 kW) with the torque of 386 Nm (39.4 kg/m or 284.9 ft/lb) – 400 Nm (40.8 kg/m or 295.2 ft/lb).

4.8 Vortec specs

Being first produced in 1999, LR4 was one of the first engines of LS series for trucks along with LM7 and LQ4. LR4 was applied for General Motor’s vans, pickups plus SUVs till 2007. The motor with 4.8-liter displacement is also referred as Vortec 4800.

These motors are reliable and can boast of great strength and are even more efficient with boost or nitrous. They can achieve 1000 hp if some updates are made.

Engine Block Specifications

Casting Numbers

12567392, 12567393, 12551358

Material

Iron

Displacement

4.8L / 293 c.i.d.

Bore Dia.

3.780 in.

Stroke

3.267 in.

Deck Height

9.230-9.240 in.

Bore Spacing

4.400 in.

Thrust Bearing Location

#3 Main

Main Cap Style

6-Bolt

Main Housing Bore Diameter

2.751 in.

Cam Housing Bore Diameter

Bore 1/5 = 2.326, Bore 2/4 = 2.317, Bore 3 = 2.307 (1999-2003)

Bore 1/5 = 2.346, Bore 2/4 = 2.326, Bore 3 = 2.307 (2004-2007)

Cam-to-Crank Centerline

4.914 in.

Rotating Assembly Specifications

Piston Material

Hypereutectic Cast Aluminum Alloy

Piston Style

Flat Top

Piston Volume

0cc

Wrist Pin Dia. (1999-2004)

0.9447 in., 0.9448 in. (Pressed)

Wrist Pin Dia. (2005-2006)

0.9429 in., 0.9431 in. (Floating)

Connecting Rod Material

Powdered Metal

Connecting Rod Style

I-Beam

Connecting Rod Length

6.275 in.

Connecting Rod Bolts

M9 x 1 x 43

Crankshaft Material

Cast Iron

Crankshaft Main Journal

2.559 in.

Crankshaft Rod Journal

2.100 in.

Reluctor Wheel

24x

Flywheel Mounting Flange (1999-2000)

1.250 in.

Flexplate Mounting Flange (1999-2000)

0.857 in.

Flexplate Mounting Flange (2001-2006)

0.857 in.

Performance Specifications

Compression Ratio 9.4:1
Horsepower Rating 255-280 hp
Torque Rating 285-295 ft./lbs.

Cylinder Head

Great cooling is provided to the cylinder head thanks to light but solid aluminum alloy it’s built of. A single chain operates camshaft while the timing chain conveys rotational movement from crankshaft to camshafts. Rocker arms, located on a pedestal, ensure valves functioning.

Inlet valves are 48 mm (1.8898 inches) while exhaust ones are 39.4 mm (1.5512 inches). Intake duration is 190 degrees with an 11.60 mm (0.457 inches) valve lift. Exhaust duration equals to 191 degrees with an 11.84 mm (0.466 inches) lift.

Years

1999-2006

Casting Numbers

862,706

Material

Aluminum

Combustion Chamber Volume

61cc

Intake Port Shape

Cathedral

Intake Runner Volume

200cc

Exhaust Port Shape

Oval

Exhaust Runner Volume

70cc

Intake Valve Diameter

1.890 in.

Exhaust Valve Diameter

1.550 in.

Cylinder Head Bolt Style

Torque to Yield (TTY)

Cylinder Head Bolt Size (1999-2003)

(8) M11 x 2 x 155, (2) M11 x 2 x 100, (5) M8 x 1.25 x 45

Cylinder Head Bolt Size (2004-2006)

(10) M11 x 2 x 100, (5) M8 x 1.25 x 45

Cylinder Block

LR4 ‘s cast iron cylinder block features a five-bearings crankshaft supported system. Diameter of crankshaft journal equals to 65 mm (2.55 inches) while crankpin is 53.3 mm (2.09 inches).

With compression ratio of 9.4, motor has cylinder bore of 96 mm (3.78 inches) and piston stroke of 83 mm (3.27 inches). Moreover, LR4 utilizes 2 compression and 1 oil control rings plus connecting rods of 159.38 mm (6.275 inches).

Valvetrain Specifications

Lifter Style

Hydraulic Roller

Lifter Link Style

Plastic Lifter Tray

Lifter Body Diameter

0.842 in.

Pushrod Length

7.385 in.

Rocker Arm Mounting Style

Pedestal

Rocker Arm Style

Die-Cast, Roller Fulcrum

Rocker Ratio

1.7

Rocker Offset

None

Valve Spring Style

Beehive

Valve Spring Color

Natural

Valve Angle

15 Degrees

Intake Valve Material

Steel – Solid Stem

Intake Valve Dia.

1.890 in.

Exhaust Valve Material

Steel – Solid Stem

Exhaust Valve Dia.

1.550 in.

Camshaft Specifications

Years

1999

2000-2006

Duration at .050 in (int./exh)

191/190

191/190

Valve Lift (int./exh)

0.457 in./0.466 in.

0.457 in./0.466 in.

Lobe Separation Angle (in degrees)

115.5

114

Cam Gear Attachment

3-Bolt

3-Bolt

Other Specifications

Intake Manifold

Truck Style

Throttle Body

78mm, 3-Bolt

Throttle Control

All Cable Operated, 1999-2002

Drive-by-Wire phased in 2003-2004, on most models

Fuel Injector Flow

1999 21.8 lb/hr., 2000 24.8 lb/hr., 2001-2006 25.2 lb/hr.

Fuel Injector Length (between O-Rings)

1.9 in.

Fuel Injector Connector

Mini-Delphi / Multec2

PCM

Warren

Crankshaft Reluctor Ring

24x

Camshaft Sensor

Rear Mount, 1x on cam

Oil Pan

Deep Rear Sump

Oil Pump

Standard Volume

Most Common Bolt-On Updates for LR4

This motor is frequently used in engine swaps because of its low cost at car dumps despite the fact that it’s not so widespread in commercial vans. If you are eager to add some modifications to your motor, you will face no troubles as LR4 is a great basis for many upgrades.

The choice of the bolt-ons for vans isn’t very vast while much more additions are obtainable for trucks. Moreover, you can find some good variants for a 5.3-liter modification.

Pretty often, car enthusiasts update cold air intake plus exhaust system. However, be ready that your motor’s sound will become so great that you won’t resist the temptation of riding faster. You will cope with all these updates yourself, but note that tune will be non-optimized.

So, it’s advisable to turn for assistance to a chassis dyno tuner and computer programmer. In such a way, a specialist will attune the ECM and make it work more efficiently no matter what fuel you buy (low octane or high quality one).

The 4.8-liter motor is prone to revving. That’s why, it’s better to increase the rev limit plus offset points. Moreover, by doing that, you will cope faster with larger camshaft and injectors tuning. Moreover, it’s crucial to mount a colder thermostat before making any further updates.

LR4 Intake Manifold and Throttle Body Modifications

Owning a power booster, intake and throttle body modifications can be postponed. But, in case your motor is naturally aspirated, deal with them before heads. Original manifold for trucks features long runners, ensuring efficient low-end torque. It’s also great that intake is ported.

Frequently, it’s undesirable to opt for a single plane way. Nevertheless, it’s reasonable if you use much nitrous as it’s prepotent and contributes to enhanced cylinder-to-cylinder mixture allocation. It’s a cool option if you apply it for an old automobile or in case you aren’t aware of injection process. You are free to clap your carburetor on it and manage a programmable ignition box, plugging directly into the original coil harness and cam sensor.

Seeking for increased power, F.A.S.T. LSXRT intake is compatible with throttle bodies of 102 mm and bigger. Moreover, truck motor bays comprise tunnel rams, changing some torque down low for more torque up high.

Written by Dan Hoffman

Dan Hoffman

Dan is a co-founder of Engineswork. He knows everything about internal combustion engines. Ask your questions in comments down below this article – he will be glad to help you anytime.

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