<VV> Fwd: valve seats

[RoboMan91324 at aol.com]

Hi Dave,
 
 
I think what you are asking about here is different from the question posed 
 about the temperature rise from ambient to that in the engine bay.  I  
contend that the differential between the ambient and bay temps is  minimal.  
What you are interested in is the bay temp in and of  itself.  Depending on 
where you live, this can be very significant.   In Minnesota, the coldest 
real temperature I experienced was minus 60 degrees  and the highest was around 
100 degrees.  This does not include wind chill  or humidity factors.  160 
degrees swing in ambient/bay temp would  definitely have an effect on your 
engine temperature and thus, your CHT.   However, if I understand your post 
correctly, you are probably wondering if  changes in the bay air temp will 
effect the accuracy of the CHT reading  .

 
I think the impact of the bay temps will be minimal on your CHT.  My  
assumption here is that you are talking about the direct interface of the air  
with your CHT.  Your CHT will be attached directly to the head either  through 
a "washer" clamped between the spark plug and the head or attached  
somewhere else to the head like the sensors on our Spyders and Corsas.  In  either 
case, the measuring device will be somewhat isolated from air flow in  that 
the thermistor will be in close contact with the head and not sticking up  
into the airstream.  A huge variation in the bay's air temp like 160  degrees 
would have an effect on the head's temperature but the CHT would still  
accurately measure the head temperature at the point of measurement.  The  only 
thing that might change would be in the system that clamps between the  
spark plug and the head because the plug sticks up into the airstream and could 
 possibly act like a cooling fin/pin.  I do not know how you might measure  
this effect but I suspect that it would be minimal considering that the 
upper  portion of the plug is covered by a rubber boot which insulates it and 
the small  amount of ceramic of the plug which lies between the head and the 
boot does  not conduct heat well.  
 
With that said, my statement is theory and you should feel free to conduct  
your test.  While you are at it, perhaps you can test the bay vs. ambient  
issue while you are at it.  This assumes that you can sample two locations  
at the same time.
 
Doc
 
1960 Corvette, 1961 Rampside, 1962 Rampside, 1964 Spyder coupe, 1965  
Greenbrier, 1966 Canadian Corsa turbo coupe, 1967 Nova SS, 1968 Camaro  ragtop

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
In a message dated 5/11/2012 6:42:09 A.M. Pacific Daylight Time,  
virtualvairs-request at corvair.org writes:

Message:  5
Date: Fri, 11 May 2012 08:03:17 -0500
From: Dave Keillor  <dkeillor at tconcepts.com>
Subject: Re: <VV> Fwd: valve  seats
To: Virtual Vairs  <virtualvairs at corvair.org>
Message-ID:
<CAHRv0RK1_Xg+7eFoGrS4ePKiTSmiJZJT-8WQ72Af43OxVMTX3g at mail.gmail.com>
Content-Type:  text/plain; charset=ISO-8859-1

Has anyone replaced "believe" with  actual measurements?  Baring any real 
data, I plan to make some  measurements when I get my restomod on the road. 
I'm interested in how engine  bay temperatures impact the cold (reference) 
junction temperatures for my CHT  gauges.

Dave Keillor

On Fri, May 11, 2012 at 7:24 AM, Ken Pepke  <kenpepke at juno.com> wrote:

>
> There are those on this  list that believe the Corvair engine bay remains
> about ambient  temperature and that all that hot sheet metal radiates 
little
> or no  heat into the bay.  You must be among that group.  I am  not.
>
> Ken P
> Wyandotte, MI
> Worry looks around;  Sorry looks back, Faith looks  up.