General Motors 8.1L Vortec V-8

GM 8.1L Vortec Engine Specs, History, & Information

The GM 8.1L Vortec is a big block V-8 based loosely on the company's flagship 454 CID engine. The 8.1L shares the 454's 4.25 inch bore but features a longer 4.37 inch stroke length. At 496 inch cubic inches of displacement, the burly 8.1L Vortec is rated between 320 to 340 horsepower and 440 to 455 lb-ft of torque, depending on the model year. For the 2001 model year, the Vortec produced within 50 lb-ft of torque of the mighty 6.6L Duramax diesel while surpassing the diesel's horsepower rating significantly.

One could argue that the Vortec's major disadvantage is its fuel economy; or lack thereof. However, those that acquire a vehicle with such an engine must obviously have needs that don't include fuel efficiency and the performance of the engine, particularly its low-end torque, is a more pertinent factor. Because the engine is only found in vehicles with a gross vehicle weight rating (GVWR) greater than 8,500 lbs, GM was not required to provide estimated fuel economy ratings through the EPA. Owners can expect to see MPGs peak in the mid-teens on the highway and drop into single digit territory with heavy towing.

The 8.1L's substantial torque rating and flat torque curve also make it suitable for marine and motorhome applications, typically as an economical option to more expensive diesel powertrain offerings. In GMC and Chevrolet SUV applications (including Suburban and Yukon 2500 models), the engine was mated exclusively to the GM 4L85E four speed automatic transmission. In Silverado and Sierra HD applications, the 8.1L Vortec was available mated to either the Allison 1000 automatic or ZF 6 speed manual transmission. GM retired the engine internally following the 2006 model year, but continued to manufacturer the engine for applications outside GM vehicles through 2009.

GM 8.1L Vortec V-8 Specs (Vortec 8100)


90° V-8

RPO Code:



2001 - 2006:
• Chevrolet Silverado 2500HD/3500HD
• GMC Sierra 2500HD/3500HD
• Chevrolet Suburban 2500 (3/4 ton)
• GMC Yukon 2500 (3/4 ton)
• Chevrolet Express 2500/3500
• Chevrolet Avalanche 2500
• Chevrolet Kodiak

2001 - 2009:
Various marine and motorhome applications


8.1 liters, 496 CID


4.25 in


4.37 in

Block Material:

Cast iron

Cyl Head Material:

Cast iron

Firing Order:


Compression Ratio:

9.1 : 1


OHV, 2 valves per cylinder

Engine Oil Capacity:

6.5 qts w/ oil filter change

Max Engine Speed:

5,000 rpm (truck/SUV applications)


2001 - 2003

340 hp @ 4,200 rpm

2004 - 2006

320 hp @ 4,200 rpm


2001 - 2003

455 lb-ft @ 3,200 rpm

2004 - 2006

440 lb-ft @ 3,200 rpm

8.1L Vortec Horsepower& Torque Curve

8.1L GM horsepower and torque curve

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8.1L Vortec V-8 vs 6.6L Duramax Diesel

Model Year

8.1L Vortec HP/TQ*

6.6L Duramax HP/TQ


340 hp/455 lb-ft

300 hp / 520 lb-ft


340 hp/455 lb-ft

300 hp / 520 lb-ft


340 hp/455 lb-ft

300 hp / 520 lb-ft


320 hp/440 lb-ft

300 hp / 520 lb-ft (LB7)


320 hp/440 lb-ft

310 hp/520 lb-ft


320 hp/440 lb-ft

360 hp/650 lb-ft

*Excludes commercial, marine, motorhome, and medium duty applications.