LT Gen V SBE Record: Chris Johnson’s 4th Gen Firebird

Chris Johnson currently holds the LT Gen V SBE record. He achieved it through careful planning, hands-on fabrication, and methodical testing. The achievement is not new, but it remains a strong benchmark for naturally aspirated LT Gen V performance. The LT Gen V SBE record was set using a stock bottom-end engine. In a segment dominated by power adders, Johnson’s Firebird stands out through efficiency, balance, and execution.

A Proven Platform With Real Results

The record-setting car is a fourth-generation Pontiac Firebird converted to LT Gen V power.
It is paired with an eight-speed automatic transmission. On the fourth pass of the initial setup, the car ran 8.90 seconds at 153.5 mph. That run was supported by clean data and consistent performance. With a 2,875-pound race weight, the Firebird stays lightweight without becoming fragile or unrealistic.

This run remains the standard within the LT Gen V SBE category because it shows what is possible when every part of the car is working together. The result was not stumbled upon. It was built, tested, and refined with intent.

Stock Bottom End, Serious Output

At the core of the LT Gen V SBE record is a 6.2L L86 truck short-block that retains its factory rotating assembly. To support the aggressive camshaft profile, the intake valves were fly-cut .215 inches deep to ensure safe piston-to-valve clearance. Static compression checks in at 14.7:1, which plays a major role in the engine’s naturally aspirated efficiency and high-rpm performance.

The combination produced 692 horsepower and 517 lb-ft of torque at the rear wheels. Those numbers matter because they were achieved without aftermarket pistons, rods, or crankshaft. It is a clear example of how far the Gen V architecture can be pushed when the supporting components are selected correctly.

Cylinder Heads, Valvetrain, And Oil Control

Airflow comes from CID cylinder heads with 46cc combustion chambers, ported by CT Porting to support high lift and sustained rpm. Valvetrain control is handled by 1.82-ratio TSP roller rockers and 7/16-inch Manton Series 3 pushrods. A hydraulic roller camshaft with .740 inches of lift ties the top end together and pushes the limits of what most would consider comfortable on a factory-based LT bottom end.

To keep everything alive at speed, the Firebird uses a five-stage dry sump system with Motion Raceworks and Fluidworks components, along with a custom-fabricated aluminum oil pan. Oil control is a critical part of this setup and a major contributor to its reliability at the track.

Drivetrain, Chassis, And Custom Fabrication

Power is routed through an 8L90 transmission equipped with a Circle D 6FPX converter and into a 12-bolt rear end with a 3.08 gear. Exhaust duties are handled by custom-modified 2-inch stainless F-body headers, converted to LT swap flanges, and finished with SPD merge collectors.

Much of what makes this LT Gen V SBE record possible comes from custom parts designed and fabricated by Chris Johnson himself. Motor mounts, water pump spacers, alternator brackets, radiator mounts, dry sump components, and even the drive-by-wire pedal bracket were engineered specifically to make the combination work as intended.

Looking ahead, Johnson has plans to test a 3D-printed intake and continue trimming weight, with long-term goals aimed at pushing the setup into the 8.60s at over 157 mph in favorable conditions. Even years later, this LT Gen V SBE record remains a reference point for what disciplined engine development can achieve.