An odd discussion came the other day related to crank pulley kits and light flywheels.

A reader told me that he wanted to replace "those cheap plastic cam gears with metal ones like they do in Australia". They prevent timing belt failures. Oh, really? I had to sleep on that one, but the next morning I woke up with the answer.

The blokes were using light flywheels and light weight pulley kits. They have no doubt gone way light. The car is jumping timing and/or breaking belts. 'Well, mate, let's put the old style metal pulleys on the car.' The "problem goes away". This plays right back into the article  <Pulley Kit>.

There is nothing cheap about the plastic timing pulleys. They are lighter, which is easier on the timing belt and they are less expensive to manufacture. What is happening is the Australian tuners have lowered the rotating mass of the engine and removed the vibration damper. The timing belt now begins to whip and fail by jumping a tooth or breaking. They are adding MASS back into the rotational system of the engine which absorbs the vibration, but is much harder on the belt than the low mass plastic pulleys.