Speaking of Timing Belts

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Don McC - 03 Mar 2009 04:58 GMT

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.

http://www.aa1car.com/library/timing_belts_interference_engines.htm

--
Don

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Chris Whelan - 03 Mar 2009 08:19 GMT

> Speaking of timing (cam) belts and chains, does anyone know which, if
> any, of the Focus engines are interference and which are
[quoted text clipped - 7 lines]
>
> http://www.aa1car.com/library/timing_belts_interference_engines.htm

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 - 03 Mar 2009 12:44 GMT

> Speaking of timing (cam) belts and chains, does anyone know which,
> if any, of the Focus engines are interference and which are
[quoted text clipped - 12 lines]
> --
> Don

You can try the "locator" at
http://www.gates.com/part_locator/index.cfm?location_id=3598&go=Interference
but 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

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