The LH6 engine is a 5.3L Gen. IV aluminum engine that replaced the LM4 in 2005. It was the first Gen. IV LS truck engine and offered Active Fuel Management (AFM).
The LH6 was available in mid-size SUVs until 2009, and in GM pickups from 2007-09. For marketing purposes, it was also known as the Vortec 5300. The engine specs and information listed here is for a stock LH6 engine.
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 LH6 engine? Check out LH6 5.3L Engine Upgrade Guide: Expert Advice for LH6 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 LH6 5.3L Vortec 5300.
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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LH6 5.3L Vortec 5300 Engine Specs
LH6 Performance Specifications
| Engine Ratings | |
|---|---|
| Compression Ratio | 9.9:1 |
| Horsepower Rating | 302-315 hp |
| Torque Rating | 330-338 ft./lbs. |
LH6 Applications
| VIN 8th Digit | Year | Make | Model |
|---|---|---|---|
| M | 2005-06 | Chevrolet | Trailblazer EXT |
| M | 2005-06 | GMC | Envoy XL, XUV |
| M | 2005-06 | Isuzu | Ascender |
| M | 2005-07 | Buick | Ranier |
| M | 2005-09 | GMC | Envoy Denali |
| M | 2005-09 | Saab | 9-7X 5.3i, ARC |
| M | 2006-08 | Chevrolet | Trailblazer |
| M | 2007-09 | Chevrolet | Silverado 1500 |
| M | 2007-09 | GMC | Sierra 1500 |
LH6 Engine Blocks
| LH6 Engine Block Specs | |
|---|---|
| Casting Numbers | 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, Bore 2/4 = 2.326, Bore 3 = 2.307 |
| Cam-to-Crank Centerline | 4.914 in. |
LH6 Rotating Assembly
| LH6 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 3 digits) | 143 |
| Crankshaft Material | Cast Iron |
| Crankshaft Part Number | 12574522 |
| Crankshaft Casting Number (last 3 digits) | 216 |
| Crankshaft Main Journal | 2.559 in. |
| Crankshaft Rod Journal | 2.100 in. |
| Reluctor Wheel | 24X (2005-06), 58X (2007-09) |
LH6 Cylinder Heads
| LH6 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 |
LH6 Camshaft Specifications
| LH6 Camshaft Specifications | ||
|---|---|---|
| Years | 2005-06 | 2007-09 |
| Part Number | 12569525 | 12625436 |
| Duration @ .050 in. (int./exh.) | Not Available | 196°/201° |
| Valve Lift (int./exh.) | Not Available | 0.481 in./0.481 in. |
| Lobe Separation | Not Available | 116°+2 |
| Cam Gear Attachment | 3-Bolt | 1-Bolt |
| Cam Gear Poles | 1x | 4x |
| Active Fuel Management (AFM) | Yes | Yes |
| Variable Valve Timing (VVT) | No | No |
LH6 Valvetrain
| LH6 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 | Plastic Guide (2005-06), Spring Loaded Tensioner (2007-09) |
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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.
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