Uncorked exhaust - warped valves

[Ted Borck <tborck@domain.elided>]

> Date: Thu, 10 Jun 1999 22:07:32 -0700
> From: "Owen" <renarac@domain.elided>
> Subject: Re: Uncorked exhaust
> 
> True. It will eventually burn the exhaust valves.


If the exhaust pipe is short enough to allow [relative] cooler air to
reach the *hot* exhaust valve(s), the exhaust valve may warp.

A warped valve will not seat properly.  Valves (especially exhaust)
are cooled by heat transfer upon intermittent contact with the valve
seat.  Sodium is also used (in high output engines) to [internally]
cool exhaust (and sometimes intake) valves.

The portion of the exhaust valve face which doesn't contact the valve
seat will not be cooled by contact with the [relative] cooler valve
seat and thus burn in that area.

Once *hot* exhaust gas blow-by occurs in the area not contacting the
valve seat, the situation gets progressively worse

If you're worried about short exhaust(s) causing valve warp, just
stuff a rag in the open exhaust pipe upon shutting down the engine.

Then go get your ear plugs for the next run. <g>


> - ----- Original Message ----- 

> From: Tom Mandera <tsm1@domain.elided>
> To: <ihc@domain.elided>
> Sent: Thursday, June 10, 1999 10:27 AM
> Subject: Uncorked exhaust
> 
> 
> > Just remembered..
> > 
> > I've been told NOT to run a motor w/o an exhaust for long, or you'll
> > burn the valves?  Something about the too-cool ambient air rushing up
> > the manifolds and into the heads when you shut the the motor doww, and
> > causing "bad things."

<snip>