Speaking of Timing Belts

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- Don McC
  
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posted
15 years ago

Tue, Mar 3, 2009 4:58 AM

Speaking of timing (cam) belts and chains, does anyone know which, if any, of the Focus engines are interference and which are non-interference?

In an interference engine, the pistons and valves share some of the same space, hopefully kept apart by the timing belt. In a non-interference engine, the pistons and valves do not share space, so a timing belt or chain failure can't result in a destroyed engine. Thus timely belt replacement is more crucial with an interference engine.

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-- Don

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- Chris Whelan
  
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posted
15 years ago

Tue, Mar 3, 2009 8:19 AM

AFAIK, all UK/European Focus engines are interference.

I don't think there are many modern cars of any make that are still non- interference. Piston /valve tolerances have to be tight to meet performance requirements, especially with a four valve per cylinder configuration.

Chris

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- Michael Pardee
  
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posted
15 years ago

Tue, Mar 3, 2009 12:44 PM

You can try the "locator" at

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I don't entirely trust it. It shows the 1985 Volvo 760T I once had as interference, but it was definitely non-interference - as were all the Volvo "red block" engine in all variants in all markets. As Chris says, most modern engines are interference because it is considered a small price for performance and efficiency.

You put it very well. Timing belt replacement is important even in non-interference engines if only because the driver is trying to get somewhere when the belt fails, but is *crucial* in interference engines.

Mike