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Accelerative forces induce cylinder imbalance in carbureted or throttle-body injected engines by steering the fuel in the direction of the force. This cylinder imbalance manifests itself as decreased performance, decreased fuel economy, and decreased reliability. Accelerative forces do not induce cylinder imbalance in port-injected engines because fuel distribution is not readily impacted. Race engines are subjected to a variety of extreme accelerative forces, including fore-aft forces during acceleration and braking, and lateral forces during cornering. It is not unusual to see forces much greater than the force of gravity. Both airborne fuel droplets and fuel deposited on the manifold walls and floor are steered by these accelerative forces, impacting engine performance and reliability adversely. In this paper, the impact of accelerative forces on combustion performance in a Winston Cup engine are examined.