Designed for large cubic-inch or high rpm drag racing Big Block Chevy combinations, these manifolds have an average runner area of approximately 4.75 sq.in. The port exits have .090" per side reduction to accommodate the wide variety of intake port sizes and require port matching to the head being used. The runners have a minimum corner radius of .500" from the plenum to the exit allowing the popular oval port shape to be used. The outside runners are shorter and straighter than competitor's manifolds and the plenum is longer front to back. These features, combined with approximately 5% taper in runner cross-sectional area, give better top end horsepower while maintaining consistency and throttle response off the stop