interference fit

[Phil@isham-research.demon.co.uk (Phil Payne)]

In message <6760C5420179440F@co.albemarle.va.us> Mark Trank writes:

> Gentlemen:  this was one of the responses I received.  Any ideas as to
> how his troubles came about?

% In theory the valves can't touch the tops of the pistons in these
% engines at any time.  But at the moment I have 5 bent exhaust
% valves that have impacted the top of the pistons in my '87 5KCSTQ.
% So much for theory.

Conventional wisdom is that there are two classes of engine;
interference and non-interference.

I expand that into three classes; non-interference, dynamic interference
and static interference.

Non-interference means what it says.  Lose the timing belt, and you
coast to a halt without a timing belt.  But _not_ without an engine.

Dynamic interference is the dangerous type - the engine is a
non-interfernce type on paper (i.e., in the books) and might even be
a non-interference type when within 'new' manufacturing tolerances.
But if the timing belt goes at speed, and on a worn engine - the
engine is toast.

Static interference is simply where the degree of interference is so
great that the crank cannot be hand-turned without a timing belt,
even on a new engine.  The loss of the timing belt is disastrous.

I think the problem occurs in the blurring of static and dynamic.

--
 Phil Payne
 phil@isham-research.demon.co.uk
 Phone: +44 385302803  Fax: +44 1536723021