<VV> Fwd: valve seats (Now Engine bay Temp)

[RoboMan91324 at aol.com]

Hi Ken,
 
I am one of those people who believe the engine bay remains relatively  
close to ambient.  Of course, this is with qualifications.   I haven't taken 
measurements so, keep in mind that this is theory but still  probable.  What 
you may be thinking of is what happens in the engine bay of  a water pumper.  
In that case, the engine is stuck in the middle of the bay  radiating heat. 
 Further, the engine bay is downstream from the engine  coolant radiator 
and in most cases the radiators for the trans cooler, A/C,  etc.  The ambient 
air in the Corvair's bay is truly outside air and the  engine is downstream 
from the bay.  In the water pumper, the engine is in  the bay and there is a 
huge temp rise from the radiators.
 
However, yes, there will be some temperature rise in the Corvair bay but I  
suspect it will be different at different parts of the bay, at different 
engine  RPM and different engine loads.
 
1. In different parts of the bay-  In the air path directly from the  air 
inlets from outside the bay through to the fan, I would think the  
temperature rise should only be a few degrees max but it depends on the  turbulence in 
the bay.  I imagine the worst case location would be in the  little pocket 
down by the crank pulley/damper because there are several heat  sources 
there and minimal air flow.  I would think air temp to the fan is  the most 
important factor in this discussion as cooling of the engine is most  important. 
 Air temp to the carbs is also a factor which is why I would shy  away from 
the individual short stack intake systems.  Pulling air in from  the upper 
part of the bay would probably result in cooler air to the  intake.  Pulling 
air in from the sides of the bay and from closer to the  heads might result 
in higher intake temperatures.
 
2. Engine RPM- This is a major factor in that it determines the  volume per 
unit time of air flow through the bay.  In effect, the amount of  air 
entering and exiting the bay goes way up as RPM increases and there is less  time 
for it to pick up heat as well as much more volume to absorb (spread) the  
heat energy.  Of course, this flow rate depends on whether the air is  
allowed to exhaust out the back.  This complicates things  significantly.
 
3. Engine load-  Obviously, the engine generates more heat as the  engine 
load goes up.  The worst case scenario would be if you are going  relatively 
slowly with a significant load such as going up a steep  incline.  You will 
have significant heat generation in the engine which  will increase 
radiation, conductive and forced convective heat  transfer.  At the same time, the 
RPM will be low which results in less  volume per unit time of air through 
the bay and engine.  It is a double  catch in that the engine is generating 
more heat which somewhat raises the temp  of the cooling air at the same time 
as it is suffering from diminished air flow  when it needs both higher 
volume and cooler air.  It is no wonder this  seems to be the situation that 
leads to the most dropped valves both during the  event as well as after many 
such cycles.
 
I would like to see some data if someone would like to perform the  
experiment.  I don't have the equipment.  I think the most important  points of 
measurement would be ambient temperature at the point of entry into  the bay 
and at the point of entry into the fan.  Secondary locations would  be ambient 
vs. the carb intake both with and without the air cleaner/ducting in  place 
as well as other locations like near the crank pulley/damper.  If  
possible, data should be taken at idle, at high RPM under high load, at high RPM  at 
low load, at low RPM under high load and at low RPM with low load.  The  
data must be recorded while each of these situations is taking place.  If  you 
pull over to take the measurements, the data is completely useless.   The 
air flow changes immediately, the air exhaust flaps close almost  
immediately, etc.  This test would require either a multi channel recording  device or 
a multi channel recording human.  It might be dangerous for the  driver to 
drive at the same time as taking measurements.  The ambient temp  must be 
recorded at the same time as the other measuring points because the  ambient 
temp will change as you drive around.  If this is not done, the  data is 
useless because if the ambient temp changes from location to location,  how can 
we measure the differential if we take only one ambient temp measurement  at 
the start of the trip?
 
A factor that would complicate things is the air exhaust flaps.   Perhaps a 
car with the air exhaust ducting and flaps removed would be the best  test 
vehicle so this variable is eliminated.
 
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:  4
Date: Fri, 11 May 2012 08:24:41 -0400
From: Ken Pepke  <kenpepke at juno.com>
Subject: Re: <VV> Fwd:  valve  seats
To: "Ron" <ronh at owt.com>
Cc: Vair Views  <virtualvairs at corvair.org>
Message-ID:  <595D41B9-6D0A-4AA8-9922-254FFA27DFD8 at juno.com>
Content-Type:  text/plain; charset=us-ascii


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.