LS Engines

LM4 5.3L Vortec 5300 Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More

LM4 engine rebuild

(Image/LS1Tech – SgtSkid)

Mechanically similar, General Motors’ LS and LS-based Vortec engines wound up on almost every branch of the GM family tree: Chevy, Pontiac, GMC, Cadillac, Buick—heck, even Saab, Hummer, and Isuzu got some LS love.

Since LS and Vortec engines are so common, they’ve become the go-to performance and swap engines of the modern era.

These motors are capable of making a lot of horsepower, and respond well to upgrades like turbos, superchargers, high-flow cylinder heads, intake systems, cams, and nitrous oxide.

[NOTE: Looking to upgrade your LM4? ReadLM4 5.3L Engine Upgrade Guide: Expert Advice for LM4 Mods to Maximize Performance.]

The aftermarket is strong, crate engines are available, and used motors are often cheaply sourced through junkyards.

Summit Racing has created a series of comprehensive guides for each engine in the LS family, so engine builders and tuners can have a handy reference for their projects.

This guide is specifically about the GM LM4 truck engine. You can find our other LS engine spec guides and LS-related tech articles here.

(Summit Racing’s Paul Spurlock and Brian Nutter contributed to this article.)

GM LM4 Engine Specs

The LM4 is a 5.3L, Gen. 3 small block engine used in GM trucks between 2003 and 2005.

It’s is very similar to the LM7, except that it’s built on an aluminum block, and the LM7 is an iron-block engine.

For marketing purposes, the LM4—like the LM7—was also known as the Vortec 5300. The information listed here is for the stock engine.

LM4 Engine Ratings
Compression Ratio9.5:1
Horsepower Rating290-300 hp
Torque Rating325-335 ft.-lbs.
LM4 Applications
VIN 8th DigitYearMakeModel
P2003-2005ChevroletTrailblazer EXT
P2003-2004ChevroletSSR
P2003-2004GMCEnvoy XL
P2004BuickRainer
P2003-2004IsuzuAscender
LM4 Block Specs
Casting Numbers12566910
MaterialAluminum
Displacement5.3L / 325 c.i.d.
Bore Dia. 3.780 in.
Stroke3.622 in.
Deck Height9.240 in.
Bore Spacing4.400 in.
Thrust Bearing Location#3 Main
Main Cap Style6-Bolt
Main Housing Bore Dia.2.751 in.
Cam Housing Bore Dia. (2003)Bore 1/5 = 2.326, Bore 2/4 = 2.317, Bore 3 = 2.307
Cam Housing Bore Dia. (2004-05)Bore 1/5 = 2.346, Bore 2/4 = 2.326, Bore 3 = 2.307
Cam-to-Crank Centerline4.914 in.
LM4 Rotating Assembly Specs
Piston MaterialHypereutectic Cast Aluminum Alloy
Piston StyleDished
Piston Volume+8cc
Wrist Pin Dia. (2003-04)0.9447 in., 0.9448 in. (Pressed)
Wrist Pin Dia. (2005)0.9429 in., 0.9431 in (Floating)
Connecting Rod MaterialPowdered Metal
Connecting Rod StyleI-Beam
Connecting Rod Length6.098 in.
Connecting Rod BoltsM9 x 1 x 43
Crankshaft MaterialCast Iron
Crankshaft Main Journal Dia.2.559 in.
Crankshaft Rod Journal Dia.2.100 in.
Reluctor Wheel24X
LM4 Cylinder Head Specs
Casting Numbers862, 706
MaterialAluminum
Combustion Chamber Volume61cc
Intake Port ShapeCathedral
Intake Runner Volume200cc
Exhaust Port ShapeOval
Exhaust Runner Volume70cc
Intake Valve Diameter1.890 in.
Exhaust Valve Diameter1.550 in.
Cylinder Head Bolt StyleTorque to Yield (TTY)
Cylinder Head Bolt Size (2003)(8) M11 x 2 x 155, (2) M11 x 2 x 100, (5) M8 x 1.25 x 45
Cylinder Head Bolt Size (2004-05)(10) M11 x 2 x 100, (5) M8 x 1.25 x 45
LM4 Camshaft Specs
Duration @ .050 in. (int./exh.)191°/190°
Valve Lift (int./exh.)0.457 in./0.466 in.
Lobe Separation Angle114°
Cam Gear Attachment3-Bolt
LM4 Valvetrain Specs
Lifter StyleHydraulic Roller
Lifter Link StylePlastic Lifter Tray
Lifter Body Diameter0.842 in.
Pushrod Length7.385 in.
Rocker Arm Mounting StylePedestal
Rocker Arm StyleDie-Cast, Roller Fulcrum
Rocker Ratio1.7
Rocker OffsetNone
Valve Spring StyleBeehive
Valve Spring ColorNatural
Valve Angle15 Degrees
Intake Valve MaterialSteel, Solid Stem
Intake Valve Dia.1.890 in.
Exhaust Valve MaterialSteel, Solid Stem
Exhaust Valve Dia.1.550 in.
LM4 Throttle Body, Fuel Injector Specs & More
Intake ManifoldTruck Style
Throttle Body78mm, 3-Bolt
Throttle ControlDrive-by-Wire
Fuel Injector Flow25.2 lbs./hr. @ 58 psi
Fuel Injector Length Between O-Rings 1.9 in.
Fuel Injector Connector Mini-Delphi / Multec2
Fuel Rail (2003)Return-Style
Fuel Rail (2004-05)Returnless
PCMWarren
Crankshaft Reluctor Ring24x
Camshaft Sensor LocationRear Mount, 1x on cam
Oil Pan
Front sump, tunnel in pan for 4WD, center filter
Oil PumpStandard Volume
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6 Comments

  1. Mike Dake says:

    What is the price of the LM4 crate engine ?

    • Hey Mike, Chevrolet Performance used to offer an LM4 crate engine under part number 12491855, but it appears to have been discontinued. So your best bet may be sourcing one through a junkyard. We’ve got
      a pair of Spotter’s Guides that may help.
      There are companies that make a few 5.3L LS crate engines (LM7), and the price range varies on whether you need just a short block or a fully-dressed long block.

  2. Matt north says:

    5,3 hiw much please long block

  3. Pingback: LM4 5.3L Engine Upgrade Guide: Expert Advice for LM4 Mods to Maximize Performance | Hotrods and Harleys

  4. Pingback: LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family - OnAllCylinders

  5. Pingback: LH6 5.3L Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More - OnAllCylinders

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