tired valve springs

[Mike Arman <armanmik@n-jcenter.com>]

Just a comment on the tired valve spring thread - 

They do get tired - the way to check them is on a little device that
measures the force needed to compress the spring to a certain height -
looks like a juice squeezer. Remember that the valve springs work very
hard, run very hot, and don't get no respect anyway. They are cheap, change
'em at rebuild time (valve job, etc.).

To go in deeper - if the spring is fatigued, it will not be strong enough
to close the valve (overcome the inertia of the valve) at high RPMs. If you
are getting valve float now and you didn't when your car was new(er), this
is why. Another problem may be that the spring is now soft enough to allow
the cam to "fling" the valve open (spring not strong enough to maintain
lifter contact with lobe of cam), and that can get expensive, too.

However, someone mentioned using 944 valve springs "cause they're stronger"
- fine, you won't get valve float at less than 50,000 RPM, but a) your
engine blew up 42,000 RPM ago, and b) your cam will wear out in three
blocks from the excessive spring pressure, wearing thorugh the hardened cam
lobe surfaces and filling you tender bearings with some very abrasive
crumbs and bits of cast iron. YMMV, but not by much.

Best Regards,

Mike Arman