The over-rev theory is interesting.
If over-revved, the valves will float.
What does that do?  Well, the valves don't actually close, so the valves are
not banging into the seats, and theoretically would endure less stress than
running at the threshold of float.

Now if the float causes mechanical interference, that's another story.

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Jake de Villiers
Sent: Sunday, May 24, 2009 10:34 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: nasty AMC exhaust valve, photos here

David

Under acceleration, if you bang it into second when you wanted fourth, you
WILL over-rev your motor - the limiter has nothing to say about it.  Or
coming downhill, say...

I remember hitting 6200RPM in fourth in my Twin Cam Fiat and banging it into
fifth - missed and got third and learned that Fiat rod bolts are good  to
~7500 RPM!

That exhaust valve was banged into and broken off so it was in the way when
the piston was coming back up, so either the keepers let go, the spring
broke or the valve was floating...

On Sat, May 23, 2009 at 11:46 PM, David Beierl <dbeierl@attglobal.net>wrote:

> At 02:16 AM 5/24/2009, Scott Daniel - Turbovans wrote:
>
>> re
>> Maybe, or maybe that's what happens when you spin your WBX to 7000 RPM on
>> a
>> missed shift!  =)