Interference Engines

• The chief difference between interference and non-interference engines lies in the valve clearance. In an interference design, the intake valves open wider and project farther into the combustion chamber while open. This larger gap allows ambient air to enter the chamber more rapidly.
  
  

Advantages

• The advantage of an interference design lies in the fact that it creates a more efficient air supply system. This efficiency in turn generates more power with a smaller engine, reducing vehicle weight and manufacturing costs.
  
  

Disadvantages

• You must change the rubber timing belt on any engine with an overhead cam design at scheduled intervals to prevent unexpected breakdown. The belt controls the timing of valve opening and closing relative to the piston cycle. It the belt in an interference engine breaks, pistons will collide with valves, resulting in several thousand dollars of repair costs.
  
  

Ford Probe

• Ford sold the Probe from 1989 to 1997 with several different four- and six-cylinder engines, some of which are interference-type engines. To determine whether a specific Probe has an interference engine, consult an online resource (see links in References section). For example, according to the Gates Rubber Company (see Resources), both the four- and six-cylinder engines in 1994 Probes are interference types, while only the four-cylinder engine is an interference design in the 1992 model year.