LR4
The LR4 was introduced in 1999. Along with the LM7 and LQ4, they were the first LS truck engines. The LR4 was available in GM pickups, vans, and SUVs until 2007. It was a 4.8L engine known as the Vortec 4800.
LM7
The LM7 was also introduced in 1999. It was available in GM pickups, vans, and SUVs until 2007. The LM7 was a 5.3L engine known as the Vortec 5300.
L59
The L59 was introduced in 2002. It was the flex fuel version of the LM7. This meant it could run E85 and gasoline. The L59 was available in GM pickups and SUVs until 2007. It was also known as the Vortec 5300.
For specific details about these engines, please follow the links below:
- Chevy LR4 Engine Specs
- Chevy LM7 Engine Specs
- Chevy L59 Engine Specs
- Upgrading the LR4, LM7, and L59 Engines
Benefits
These engines are strong and durable. Many people use them with boost or nitrous. With upgraded internals, the blocks can handle over 1,000 hp.
The engines all have a 3.780 in. bore diameter. The cylinders canbe bored toLS1 size (3.898 in. +). However, that will thin out the cylinder walls. A smaller bore size will keep the block strong and rigid.
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, these engines are identical. The differences are listed in the table below.
| RPO Code | Piston Style | Stroke | Rod Length | Injector Length (O-ring to O-ring) |
| LR4 | Flat Top | 3.267 in. | 6.275 in. | 1.9 in. |
| LM7 | Dished | 3.622 in. | 6.098 in. | |
| L59 | 2.5 in. |
If you don't have the VIN code, you will need to inspect the pistons, fuel injectors, crankshaft, or connecting rods. Checking pistons requires removing the cylinder heads or using a Borescope. Checking the crank and rods can be done by pulling the oil pan.
Special Notes
- The 1999-2000 LR4 with a manual transmission had a crankshaft with a 1.250 in. long rear flange. (Casting #12553312)
- All other LR4's had a crankshaft with a 0.857 in. rear flange. (Casting #12553482)
- All LM7 and L59 engines had a crankshaft with a 0.857 in. rear flange. (Casting #12552216)
- In 2001, the LR4 and LM7 were upgraded with MLS gaskets.
- The L59 was first built after the upgrade. It always had MLS gaskets.
- The 1999-2003 LR4 and LM7 had a return-style fuel injection system.
- They went returnless in 2004 (except the Express, Trailblazer, and Envoy).
- The 2002-2004 L59 had a return-style fuel injection system and 50 psi of rail pressure.
- They went returnless in 2005 and had 58 psi rail pressure.