The LH8 is a 5.3L Gen. IV aluminum block engine truck engine that appeared in 2008-09 GM trucks, including the Hummer H3, Chevy Colorado, and GMC Canyon.
The engine specs and information listed here is
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.
[Looking to upgrade your LH8 engine? Check out LH8 5.3L Engine Upgrade Guide: Expert Advice for LH8 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 specific guide is for the GM LH8 5.3L engine.
You can find more LS engine spec guides and LS-related information here.
(Summit Racing’s Paul Spurlock and Brian Nutter contributed to this article.)
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LH8 5.3L Engine Specs
LH8 Performance Specifications
| LH8 Engine Ratings | |
|---|---|
| Compression Ratio | 9.9:1 |
| Horsepower Rating | 300 hp |
| Torque Rating | 325 ft.-lbs. |
LH8 Applications
| LH8 Applications | |||
|---|---|---|---|
| VIN 8th Digit | Year | Make | Model |
| L | 2008-09 | Hummer | H3 |
| L | 2009 | Chevrolet | Colorado |
| L | 2009 | GMC | Canyon |
LH8 Engine Block Specs
| LH8 Block Specs | |
|---|---|
| Casting Number | 125771048, 12601900, 12569513, 12568573 |
| Material | Aluminum |
| Displacement | 5.3L / 325 c.i.d. |
| Bore Dia. | 3.780 in. |
| Stroke | 3.622 in. |
| Deck Height | 9.240 in. |
| Bore Spacing | 4.400 in. |
| Thrust Bearing Location | #3 Main |
| Main Cap Style | 6-Bolt |
| Main Housing Bore Dia. | 2.751 in. |
| Cam Housing Bore Dia. | Bore 1/5 = 2.346 in. Bore 2/4 = 2.326 in. Bore 3 = 2.307 in. |
| Cam-to-Crank Centerline | 4.914 in. |
LH8 Rotating Assembly
| LH8 Rotating Assembly Specs | |
|---|---|
| Piston Material | Hypereutectic Cast Aluminum Alloy |
| Piston Style | Flat Top |
| Piston Volume | 0cc |
| Wrist Pin Dia. | 0.9431 in. (Full Floating) |
| Connecting Rod Material | Powdered Metal |
| Connecting Rod Style | I-Beam |
| Connecting Rod Length | 6.098 in. |
| Connecting Rod Housing Bore | 2.225 in. |
| Connecting Rod Bolts | M9 x 1 x 43 |
| Connecting Rod Part Number | 12649190 |
| Connecting Rod Casting Number (last three digits) | 143 |
| Crankshaft Material | Cast Iron |
| Crankshaft Part Number (Last 3 Digits) | 12588614 |
| Crankshaft Casting Number (last three digits) | 216 |
| Crankshaft Main Journal Dia. | 2.559 in. |
| Crankshaft Rod Journal Dia. | 2.100 in. |
| Reluctor Wheel | 58x |
LH8 Cylinder Heads
| LH8 Cylinder Head Specs | |
|---|---|
| Casting Numbers | 799, 243 |
| Material | Aluminum |
| Combustion Chamber Volume | 65cc |
| Intake Port Shape | Cathedral |
| Intake Runner Volume | 210cc |
| Exhaust Port Shape | D-Port |
| Exhaust Runner Volume | 75cc |
| Intake Valve Diameter | 2.000 in. |
| Exhaust Valve Diameter | 1.575 in. |
| Cylinder Head Bolt Style | Torque to Yield (TTY) |
| Cylinder Head Bolt Size | (10) M11 x 2 x 100, (5) M8 x 1.25 x 45 |
LH8 Camshaft Specs
| LH8 Camshaft Specs | |
|---|---|
| Part Number | 12625437 |
| Duration @ .050 in. (int./exh.) | 191°/190° |
| Valve Lift (int./exh.) | 0.457 in./0.466 in. |
| Lobe Separation Angle | 114° |
| Cam Gear Attachment | 1-Bolt |
| Cam Gear Poles | 4x |
| Active Fuel Management (AFM) | No |
| Variable Valve Timing (VVT) | No |
LH8 Valvetrain
| LH8 Valvetrain Specs | |
|---|---|
| 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. | 2.000 in. |
| Exhaust Valve Material | Steel, Solid Stem |
| Exhaust Valve Dia. | 1.575 in. |
| Timing Chain Guide Style | Spring Loaded Tensioner |
LH8 Throttle Body, Fuel Injector Specs & More
| LH8 Throttle Body, Fuel Injector Specs & More | |
|---|---|
| Intake Manifold | Truck-Style |
| Throttle Body | 87mm, 4-bolt |
| Throttle Control | Electronic, Drive-by-Wire |
| Fuel Injector Part Number | 12580681 |
| Fuel Injector Flow | 30 lb./hr. @ 58 psi |
| Flex Fuel Capable | No |
| Fuel Injector Length Between O-Rings | 1.870 in. |
| Fuel Injector Connector | EV6 / USCAR |
| PCM | E67 |
| Crankshaft Reluctor Ring | 58x |
| Camshaft Sensor Location | Timing Cover |
| Oil Pan | Varies by Application |
| Oil Pump | High Volume (1.25 c.i. per rev.) |
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NOTE: You can find engine specs and detailed engine upgrade advice for every LS and LS-based Vortec truck engine in one place: The Definitive Guide to LS Engine Specs and LS Engine Upgrades.
[…] LH8 5.3L Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More […]
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