The 427 IR ROUSH crate engines are built on the same general engine concepts that emerged in the 1960s and continued through later decades. Still, modern manufacturing and performance upgrades have pushed them well beyond original factory limits. These engines produce significantly more horsepower and torque than the production versions they’re based on. Because of that, they can behave differently in terms of throttle response, load demands, and overall power delivery. The design feels classic, but the performance is unmistakably modern.
