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.
[…] LH6 5.3L Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More […]
Can I swap in a LM4 for a blown LH6?
Yes and no will need dod shut off in pcm/needs tuned. And timing reluctor swap or just tuned. Lol
Great oil press hot. Less cold. Bottom noise worse when or after hot.Any known pump or strainer problems? About to pull pan to look. Any advise? Runs strong!
Check the O-ring on the oil pump pick up tube where it mounts to the pump. These are usually split or badly cracked. Got this tip from a Richard Holdener YouTube segment.
Can I swap lh6 24x with a lh6 58x and have it work?
06 envoy Denali with a 2010 lh6.
Thank you
Yes Texas speed has what you need! Get at them and they will be happy to help.
Or just get it tuned for the reluctor count and you’re good to go.
How/where to tune the reluctor count going from an 07 58x engine to an 06 24x ECM?
You can’t tune the computer for the different reluctor wheel counts 24x vs 58x, that is incorrect. You can step down from the newer 58x to 24x with a Lingenfelter TRG-002 conversion box, but the computer will otherwise not work with 58x signal. You also cannot go the other way and run a 24x engine in a newer 58x application, there is no conversion for that. (posting for future researchers)
I want to swap my Lh6 to get away from DoD what engine can I use ? I have a 06 envoy Denali
Just delete the DOD. I swapped to an LS9 cam and deleted the DOD. Retuned.
My 2006 trailblazer 5.3 has a cast block do you have them in a short block.Also how much
buen dia, quiero eliminar el AFM . DOD de mi motor LH6 5.3 , se puede hcer?…….como se hace?
es para una GMC envoy 2008
i have a lh6 with upgraded cam (btr ls1 stage 1) and caddy racing lifters, would it be beneficial to upgrade the oil pump to a melling high pressure pump. or does the stock provided adequate oiling.
also any recommendation on upgraded rocker arms. i have comp cams trunnion kit in stock arms but its starting to make noise. car sits most the time and is noisier when first started.
i thinking they might be not getting lubed up good.
I have a fully loaded 05 trailblazer ext, 286,xxx km on it. My way home from visiting family two nights so I started to hear a clunking/knocking sound. I was ten minutes from home and probably shouldn’t have kept going but vehicle shut off slut 3 blocks from home. Sunny turn over, till over nothing. The key clicks once and I get power to everything (till the battery dies) I’m guessing a piston or two went and my engine is shot. My question is do I sell it to national salvage for the steel, try part it out, or any suggestions?
If I wanted to backwardly convert a 2006 LH6 to an 2004 spec LM3, would this be doable? I have an LH6 from an ’06 Envoy that I want to re-seal, and do some perf upgrades to, before installing it into the currently LM3 equipped 2004 Buick Rainier. Thanks.
How do I properly Identify my engine. As a LH6 5.3 it should have the 8th digit M. My engine is parted out from a new unsold 2009 Hummer.
5GTEN63L788201075
02/15/08
It’s a learning curve, I’d like to make it a torque monster like the old 302.
Hey Barry, this should help you out: How to Identify an LS Engine