How to Get More Horsepower From a 7.4 Literby Alexander Eliot
An engine's horsepower output is ultimately decided by the amount of air and fuel it can combust. For this reason, a large engine with 7.4 liters of displacement, such as the various big block crate engines produced by Chevrolet, have a very high horsepower potential. The displacement measurement is the amount of air ingested by an engine with one crank revolution. That means that your 7.4-liter V8 engine takes in 7.4 liters of air for each combustion cycle -- over twice the amount taken in by the average four-cylinder or six-cylinder production engine. Installing bolt-on intake and exhaust modifications to your 7.4-liter engine can help the engine breathe an even larger amount of air, improving horsepower and overall efficiency.
Replace your 7.4-liter's stock air intake with a performance intake system. Stock intakes are often restrictive and tuned for easy maintenance and noise reduction. Performance intakes utilize larger-diameter tubing and high-flow air filters to help the engine breathe easier. Often, performance intake systems will also relocate the air filter to a cooler, ambient air source, such as the front bumper.
Complete your 7.4-liter engine's modified intake track by installing a high-flow throttle body and intake manifold. The throttle body is actuated by the throttle pedal, allowing airflow to pass into the intake manifold. The air is then directed into the cylinder heads, where it's drawn in by the pistons for combustion. Swapping out your 7.4-liter's stock throttle body and intake manifold for higher-flower units compliments the modified air intake system by fully optimizing your engine's intake track for performance.
Replace the stock exhaust headers with high-flow units. The headers direct the exhaust out of the engine toward the rear of the vehicle. High-flow headers feature large-diameter, volumetrically tuned piping that will allow your engine to expel exhaust gases more efficiently, increasing horsepower. Depending on local and state laws, high-flow catalytic converters can also be installed in place of the stock units, which will compliment the high-flow nature of your modified headers.
Complete your modified exhaust system with a high-flow cat-back exhaust system. The cat-back exhaust system bolts to the catalytic converters, leading exhaust to the rear of the vehicle, where it exits through the mufflers. If your 7.4-liter engine currently has a single exhaust piping setup, converting it to a dual exhaust will maximize exhaust flow potential. Dual exhausts feature individual exhaust piping systems from the header all the way to the rear of the car. This allows for the least amount of exhaust turbulence, maximizing horsepower gains.