LQ4
The LQ4 was introduced in 1999 as one of the first LS truck engines. It was available in GM pickups, vans, and SUVs until 2007. The LQ4 was also known as the Vortec 6000.
LQ9
The LQ9 was an improved, high-output version of the LQ4. It was introduced in 2002 for the Cadillac Escalade. It was available in the Escalade and GM pickups until 2007. The LQ9 was also known as the Vortec HO 6000 or the VortecMAX.
For specific details about these engines, please follow the links below:
Benefits
Both these engines are strong and durable. Many people use them with boost or nitrous. With upgraded internals, the block can handle over 1,000 hp. The down side is the weight. At 216 lbs., the block is about 100 lbs. heavier than the aluminum LS1 block.
What’s the Difference?
The easiest way to tell the difference is to check the 8th digit of the VIN code.
- Follow this link to Identify an LS Engine by VIN.
Externally, the engines are identical. The only differences were:
- The LQ4 came with dished pistons.
- The LQ9 came with flat top pistons. (This raised the compression ratio, horsepower, and torque.)
- The LQ9 had injectors with a slightly higher flow rating.
If you don’t have the VIN code, you will need to inspect the pistons. This means removing the cylinder heads or using a Borescope.
Special Notes
- The 1999-2000 LQ4 had cast iron cylinder heads.
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- All others had aluminum heads.
- The 1999-2000 LQ4 had a 1.250 in. thick rear flange on the crankshaft.
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- All others had a 0.857 in. thick rear flange.