Fix It

Chevrolets 454 Big Block engine has been through several phases over its production span. The engine began as a major player in the muscle car wars of the 1970s, gaining notoriety for its ability to generate serious horsepower and torque. Displacing 7.4 liters, this V8 was never intended to be fuel efficient, but rather was paired with a four barrel carburetor for maximum output.

Background

In the height of the muscle car era, as car manufacturers focused on designing engines that were larger and faster, Chevrolet introduced the 454. This throaty powerplant was reserved for high performance upgrades on Camaros, Chevelles and Corvettes. The 454 especially enhanced the reputation of the Chevelle as a muscle car.

Shortly after its introduction, climbing gas prices and increased regulation on auto emissions influenced auto makers to focus on smaller engines. The 454 was transferred to Chevys truck line and used in its heavy-duty half and three-quarter ton pickups. In the mid-1990s the engine was redesigned and renamed the Vortec 7400, before being phased phased out of production in 2000.

Performance Specifications

The 454 was available as an LS5, LS6 and LS7 in the 1970s. The most powerful version available to the public was the 1970 LS6. When installed in the Chevelle or Camaro, this engine could deliver 450 horsepower at 5,600 rpm. In the Chevelle, the LS6 had a maximum torque of 500 ft-lbs at 3,200 rpm. Camaros could also achieve this torque at 3,600 rpm. The horsepower was decreased when the 454 was transferred to pickup trucks. When the 454 was first introduced as the Vortec 7400 in 1996, it was rated at 290 horsepower.

Engine Specifications

This 7.4 liter engine is one of the larger engines made by Chevrolet. The 1970 to 1974 high performance versions had a 4.00-inch stroke and 4.251-inch bore. The timing order is 18436572, with a distributor cap that spins clockwise. Engine oil is the primary lube or sealer, and is used on the main caps, connecting rod bolts, cylinder heads, oil pump and pan, timing cover, valve cover, centerbolt and on the bellhousing between the transmission and the engine block.

The SuperTrapp exhaust on many Big Dog motorcycles is a tunable exhaust. Most motorcycle exhausts use baffle tubes and chambers to modify the exhaust stream. The baffles make the exhaust change direction and slow down. Slower exhaust is quieter because the exhaust stream contacts high frequency absorbing packing materials longer. SuperTrapp exhausts modify the last stage of exhaust flow with tuning discs. The gap between the discs is smaller on the inside than the outside. The idea is to create expansion chambers with the discs which increases what is usually called the "scavenging effect" of an exhaust system on engine exhaust. This is how to replace and tune all modifiable parts in a SuperTrapp two into one exhaust.

Instructions

1

Loosen and remove the three end cap Allen screws from the end of the exhaust with an Allen socket and socket wrench. Remove the end cap and disc stack.

2

Remove and keep handy the two Allen screws on the bottom of the exhaust outlet. Remove the SuperTrapp core assembly from the muffler body.

3

Slide the replacement core assembly into the muffler shell. Align the screw holes in the new core with the screw hole in the muffler shell.

4

Secure the new core in the muffler shell by reinstalling the two Allen screws with an Allen socket and wrench. Tighten the screws to 20 inch- pounds of torque with the Allen socket and a torque wrench.

5

Count the stackable discs in your disc stack assembly. Your exhaust may contain as many as 20 discs or as few as 12. SuperTrapp suggests you experiment with different numbers of discs until your engine finds its "sweet spot."

6

Stack the discs you decide to use inside the muffler end cap. The flat surface of the discs should face the core assembly.

7

Apply SuperTrapp brand high temperature lubricant or its equivalent to the Allen screw threads. Replace the end cap and disc assembly in the end of the muffler.

8

Tighten the Allen screws to 20 inch-pounds of torque with the Allen socket and a torque wrench. Test the performance of your motorcycle on the road.