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Pistons hitting valves
In message <firstname.lastname@example.org> Brendan writes:
> I've heard and read about the concern of pistons hitting the valves when
> the timing belt breaks (or when changing the belt, I suppose). I was told
> by a mechanic that the engine (or perhaps it's in the design of the heads?)
> in my '87 5ksq was designed such that this was not a concern because the
> valves didn't drop down far enough or the pistons rise high enough for them
> to clash. Can anyone confirm this, or is anyone aware of which (if any)
> Audi engines were designed this way?
Your engine is a non-interference type. In theory, nothing bad can happen if
the timing belt breaks.
However - many of us suspect that a worn engine may (via crank journal, big and
little end wear) _become_ an interference engine in later life. There's also
the issue of speed - an engine that can be turned by hand without interfering
might well interfere if the parts are being flung about at 6500 rpm.
So the only _safe_ approach is to treat all Audi engines as interference
types. Your mechanic's theory is correct - but none of the regulars here would
rely on it.
Committee Member, UK Audi [ur-]quattro Owners Club