The Chevy L31 is a 5.7-liter V8 engine that belongs to General Motors’ Vortec family. Introduced in 1996, it was used primarily in Chevrolet and GMC trucks, SUVs, and vans. The L31 Vortec 5700 is known for its strong low-end torque, reliability, and widespread aftermarket support, making it a favorite among enthusiasts and engine builders.
Chevy L31 5.7L Vortec Engine Specifications
| Specification | Details |
|---|---|
| Engine Code | L31 (Vortec 5700) |
| Production Years | 1996–2002 |
| Displacement | 5.7 L (5,733 cc) |
| Configuration | V8 |
| Block Material | Cast Iron |
| Cylinder Head Material | Cast Iron |
| Bore x Stroke | 101.6 mm × 88.4 mm (4.00 in × 3.48 in) |
| Compression Ratio | 9.4:1 |
| Valvetrain | OHV, 16 valves (2 valves per cylinder) |
| Fuel System | Sequential Multi-Port Fuel Injection (MPFI) |
| Aspiration | Naturally Aspirated |
| Ignition System | Distributor-based (High-Voltage Switch Ignition) |
| Horsepower | 255 hp (190 kW) @ 4,600 rpm |
| Torque | 330 lb-ft (447 Nm) @ 2,800 rpm |
| Oil Capacity | 5.0 quarts (4.7 liters) with filter |
| Recommended Oil Type | 5W-30 (10W-30 for high-mileage engines) |
| Cooling System | Liquid-cooled |
| Fuel Type | Gasoline |
| OEM Spark Plugs | AC Delco R44LTS6 |
| Timing Mechanism | Timing Chain |
| Firing Order | 1-8-4-3-6-5-7-2 |
Engine Configuration and Components
Cylinder Heads and Valvetrain
The L31 Vortec heads are one of its standout features. These high-flow iron heads provide better intake and exhaust flow compared to older small-block Chevy designs.
- Two-valve-per-cylinder design
- 1.94-inch intake valves and 1.50-inch exhaust valves
- Improved combustion chamber shape for increased efficiency
The OHV pushrod design makes maintenance simple while ensuring high durability and longevity. However, the stock valve springs can limit high-RPM performance, making upgrades necessary for performance builds.
Fuel Injection System
The L31 uses a sequential multi-port fuel injection (MPFI) system, an upgrade over the older throttle-body injection (TBI) found in previous small-block Chevy engines. This system offers:
- Better fuel atomization
- Improved throttle response
- Increased fuel efficiency compared to TBI systems
However, the spider-style MPFI assembly can develop injector failures over time, leading to rough idle, hesitation, or misfires.
Crankshaft and Bottom End
The L31 crankshaft is a nodular iron unit with a one-piece rear main seal, designed for strength and durability.
- Connecting Rods: Forged steel
- Pistons: Hypereutectic aluminum
- Oil System: Wet sump
This bottom-end design allows the L31 to handle moderate power upgrades without significant internal modifications.
Common Applications
The L31 was primarily used in Chevrolet and GMC trucks and SUVs, including:
- 1996–2002 Chevrolet/GMC C/K 1500, 2500, 3500
- 1996–2000 Chevrolet Tahoe/GMC Yukon
- 1996–2002 Chevrolet Express/GMC Savana Vans
- 1996–1999 Chevrolet Suburban/GMC Suburban
- 1999 Cadillac Escalade (First Generation)
This engine was later phased out in favor of the LS-based Vortec 5300 (LM7) in 2002.
Service Intervals and Maintenance Guide
Regular maintenance is crucial to ensure the longevity and reliability of the L31 engine. Below are the recommended service intervals:
Oil and Filter Changes
- Interval: Every 5,000–7,500 miles (8,000–12,000 km)
- Recommended Oil: 5W-30 synthetic or conventional
- Oil Capacity: 5.0 quarts (4.7 liters) with filter
Older engines with higher mileage may benefit from 10W-30 oil to reduce oil consumption and wear.
Spark Plugs and Ignition System
- Interval: Every 30,000–50,000 miles (48,000–80,000 km)
- Recommended Plugs: AC Delco R44LTS6 or equivalent
- Ignition Wires & Distributor Cap: Inspect and replace if needed
A failing distributor cap or ignition coil can cause misfires and hesitation.
Cooling System
- Radiator Flush: Every 50,000 miles (80,000 km)
- Thermostat Replacement: Every 100,000 miles (160,000 km) or when overheating issues arise
- Water Pump Inspection: Check for leaks or bearing wear every 30,000 miles
A common issue with the L31 is intake manifold gasket failure, leading to coolant leaks and overheating. Upgrading to improved aftermarket gaskets can prevent this problem.
Fuel System Maintenance
- Fuel Filter Replacement: Every 30,000 miles (48,000 km)
- Fuel Injector Cleaning: Every 50,000 miles (80,000 km)
- Check Fuel Pressure Regulator: If experiencing hard starts or hesitation
Faulty MPFI injectors can lead to fuel leaks and rough idling. Upgrading to marine-style injectors improves durability and performance.
Timing Chain and Accessory Drive
- Serpentine Belt Replacement: Every 60,000–100,000 miles (96,000–160,000 km)
- Timing Chain Wear Inspection: Every 100,000 miles
Though timing chains typically last the life of the engine, excessive slack can lead to poor timing and rough performance.
Common Problems and Reliability
The Chevy L31 5.7 L is known for its durability, but a few common issues include:
- Intake Manifold Gasket Leaks – Causes coolant leaks and overheating
- Fuel Injector Failures – Stock MPFI system prone to clogging and leaks
- Distributor Wear – Leads to timing issues and misfires
- Oil Leaks from Valve Covers – Common on high-mileage engines
Despite these concerns, the L31 Vortec is a highly reliable engine when properly maintained.
Conclusion
The Chevy L31 Vortec 5.7 L is a durable, high-torque engine designed for workhorse applications. With proper maintenance and regular servicing, it can last well over 250,000 miles. Its simple OHV design, strong bottom end, and improved Vortec heads make it a great engine for both stock and performance applications. Whether used in a classic truck, van, or a custom swap, the L31 remains a highly respected small-block V8 in Chevrolet’s lineup.
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