There are two types of engines that use timing belts. They are described as: "Interference Engines" and "Non-interference Engines" The difference lies in the proximity between the valves and the pistons. On an interference engine, if the timing belt slips even one notch, the piston can crash into an open valve causing serious engine damage by bending valves and breaking pistons. Non-interference engines will usually not self destruct, but in either case if the belt fails, the engine will immediately shut down leaving you stranded.
I personally changed my timing belt on my 98 Escort. It was a pain but it saved me money!
Here's a list of engines that would be damaged by a timing belt failure while driving. Not sure if it's complete. But may be a good start.
1981-85 1.6L Escort, EXP
1981-83 1.6L LN7, Lynx
1984-85 2.0L Escort, Tempo
1993-95 2.0L Probe
1986-88 2.0L Ranger
1984-87 2.0L Lynx, Topaz Diesel
1985 2.2L Ranger
1989-92 2.2L Probe
1986-88 2.3L Ranger
1986-87 2.3L Diesel Ranger
1991-98 4.6L Crown Victoria
Monday, December 7th, 2009 AT 1:12 PM