In response to the Chevrolet Camaro's success in the SCCA Trans-Am series, Ford engineers developed a new racing engine from the small block. The first attempt mated a tunnel-port head to a 289 cu in block, but the displacement proved to be too small to deliver the desired power. The next iteration of the engine mated an improved head design to the 302 cu in block, producing the famous "Boss 302". The heads from the Boss 302 became the production heads on the 335-series Cleveland engines, which used the same bore spacing and head bolt configuration as the small block engines.