The basic principles of the internal combustion engine haven’t really changed over the years – it’s still the typical suck, squeeze, bang and blow. We’ve seen advancements in technology to improve the efficiency of engines, such as the increased accuracy of fuel injection systems and the common rail diesel injection, but the underlying principles have always been the same. The crankshaft still drives the camshaft through a chain or cambelt to keep the engine components in time while running.

Up until the 1970s, it was common for cars to have a chain driven camshaft, but in the 90s the cambelt was adopted to help reduce the noise of engines.

In the last decade, manufacturers like Subaru and Mazda have chosen to revert back to the chain system, which reduces maintenance costs and allows more compact engine designs. A considerable amount of time and effort was spent in introducing improvements that eliminate many of the drawbacks of the older systems.

Cambelts

Cambelts, or timing belts, are made out of rubber and high tensile fibre, so they’re usually quieter than cars that are chain driven. Typically they’ll need to be replaced between 60,000 and 100,000kms, but it can also depend on the age of the cambelt and the manufacturer’s specifications should be taken into consideration as well. Most systems will also include other components that may need to be periodically replaced, such as the idler and tensioner bearings or water pump. This can be a little bit expensive and so it’s important to budget for it and to keep on top of the manufacturer’s replacement interval schedule. If you don’t replace components and they later fail, it can leave you open to potentially catastrophic engine damage.

Chains

Chains (or timing chains) are back in fashion, and cambelts are becoming few and far between. Even though chains lasted longer and were stronger, the older systems used to rattle and tended to generally emit more noise, particularly as the engine became more worn down.

Chain systems have improved dramatically though, with manufacturers introducing new and innovative ways to reduce noise.

As well as changing the material used, they’ve improved the tensioning system through the introduction of oil pressure and spring-loaded tensioners which helps to keep the chain taut and quiet. Modern engines also employ large chain guides to silence the chain and minimise vibrations.

While chains don’t tend to break, they can stretch over time due to wear and tear. Look out for signals of a stretched chain like rattling noises from the chain cover, and engines that are slow or hard to start. Some vehicles even have an engine management sensor which alerts you with a warning sign on the dashboard if the camshaft and crank shaft are no longer synchronised with one another.

Chains are designed to require less maintenance, which means that servicing costs will be less but, if a chain does become worn, the cost of replacement can be significantly higher than that of a regular cambelt replacement. It’s important to note though that this is a rare occurrence, and so the general maintenance of a chain-driven vehicle is likely to be less than that of a car with a cambelt.

Developments

Developments for alternative valve train systems have been tested by a Swedish company called FreeValve. Since the early 2000s, they have been developing and testing systems with no camshafts. While there may be many advantages of these engines, there are clearly still some hurdles that need to be overcome – we are yet to see a road vehicle produced that uses this type of technology.

Both chain and cambelts do the same thing, but the desire of low maintenance costs from consumers has seen the increased popularity of chain systems in cars. Along with other improvements to engine components to increase fuel efficiency.

How can the AA help?

• AA Auto Centre - aa.co.nz/autocentre
• AA Roadservice - aa.co.nz/roadservice

Vehicle experts you can trust