 Not all engines have push rods, some operate by allowing the camshaft to push directly onto the valves, these are called modular engines.In 1996 Ford introduced their new 4.6 liter modular engines, these were the first of their kind to become popular.When push rods fail in an engine they usually bend, which causes an issue that will not allow the engines valves to open completely causing the engine to be down on horsepower.