[DeTomaso] head drilling for air release

John Taphorn jtaphorn at kingwoodcable.com
Thu Sep 3 20:33:05 EDT 2009 

Let me offer another perspective on restricting coolant flow.  I am 
skeptical that restricting flow helped Mike's cooling issue; rather I am 
prone to believe it was coincidental to another change that may have 
inadvertently occurred, such as removal of trapped air.

Trapping water in the motor to absorb more heat doesn't work very well.  As 
the trapped water gets hotter, it's ability to absorb additional heat energy 
slows.  The greater the temp differential between the block and the water, 
the more efficiently the water will absorb additional heat energy.  Thus, it 
will always be better to get cooler water from the radiator into the block. 
If you could magically remove the just introduced water within seconds and 
replace it with cooler water, cooling efficiency would always improve.  Put 
another way, cooler water will always absorb more heat than warmer water at 
the same elevation.  Thus, it is NEVER better to slow or trap water in the 
block.

Now, lets look at the other end.  The radiator cools more efficiently when 
the difference between the temperature of the water in the radiator and the 
air's temperature (ambient) flowing through it's fins is greatest.  As 
coolant flows through the radiator and cools, the difference between coolant 
temps and ambient air decreases.  In a two pass system, the coolant temp 
drop is greater on the first half than on the second pass.  On a single 
pass, the reduction in coolant temps is greater on its journey across the 
first half of the radiator then the second half.  Again, as the coolant 
passes through the radiator and the coolant temperature falls, it is a 
greater challenge for the ambient air to cool the coolant each successive 
degree.  The logical concomitant is that introducing newly released from the 
engine hotter coolant to the radiator with a higher temperature difference 
to ambient is better than trapping cooled coolant in the radiator longer 
trying to drop additional heat energy.

It is true that the idea of slowing coolant to gain more heat in the block 
and release more in the radiator is compelling on its face and explains why 
the misunderstanding has survived as long as it has.  However, it qualifies 
as a myth or legend in conflict with the laws of thermodynamics.

As others have said on this forum.  It is all about flow.  You cannot get 
enough - you cannot get to much.  The added benefit of greater coolant flow 
is increased coolant turbulence against the surface it is trying to extract 
or expel heat.  Greater turbulence enhances heat transfer.

JT

----- Original Message ----- 
From: <asajay at asajay.com>
To: <detomaso at realbig.com>
Sent: Thursday, September 03, 2009 10:29 AM
Subject: Re: [DeTomaso] head drilling for air release


> Michael, I agree with that analysis.  All I'm trying to do at this
> point is establish positive coolant flow.  If I take the thermostat
> out, I should -see- positive flow in the swirl tank.  If I see the
> flow, then I know there are no restrictions and it supports the idea
> of the thermostat being the culprit.  Once established, I can then
> install a known good thermostat (after a boil test that is) and try
> again.
>
> Asa Jay
>
> Quoting "michael at michaelshortt.com" <michaelsavga at gmail.com>:
>
>> Asa,
>> If overheating is THE problem, then running without anything in the
>> thermostat's location isn't going to help much IMHO.  I had the same 
>> problem
>> many years ago with my 1970 Mach 1 with a 351C when I went to the drag 
>> strip
>> and had major overheating problems.  I thought that pulling it out would
>> solve the problem and a kindly old racer ( probably my age now ) came 
>> over
>> when I was standing there cussing at a steaming car and explained to me 
>> that
>> by pulling it out and letting the water just run through didn't allow the
>> water to remain in the radiator long enough to get much cooler.  He's the
>> one that turned me onto those big Gold washer looking things sold by Mr.
>> Gasket ( in a three pack as I recall of various hole sizes ) that
>> were restrictors made to replace the thermostat and only allow so much 
>> water
>> to get into the radiator ( thus I imagine creating some back pressure ) 
>> but
>> by slowing the incoming volume going in at the top did allow the water to
>> stay a little longer inside the cooling fins and thus get a little 
>> cooler.
>>  I'm no thermodynamic engineer, but it worked.  After I install those, it
>> never overheated again and that car in those days was also my daily 
>> driver
>> and I left the rings in until winter when a thermostats needed to
>> be reinstalled ( because NC in the winter does get cold ).
>>
>>
>> Michael Shortt
>>
>>
>>
>> On Thu, Sep 3, 2009 at 10:03 AM, Asa Jay Laughton <asajay at asajay.com> 
>> wrote:
>>
>>> Chris, I appreciate the offer.  If needed, I have a Harbor Freight near
>>> me.  I really need to get the thermostat out and check it.  I'll then
>>> reseal the housing without a thermostat and run the car to see what
>>> happens.  (I'll also boil test the thermostat).  I don't believe my
>>> issue was a mongo-bubble holding up the fluid flow  (I'm a fan of
>>> drilling a hole in the thermostat to assist air bleed).
>>>
>>> Asa Jay
>>>
>>> Asa Jay Laughton, MSgt, USAFR, Retired
>>>
>>> & Shelley Marie
>>> Spokane, WA
>>>
>>> 1971 Mach I Mustang  [ASA JAY]
>>> 1973 Pantera L 5533  [ASASCAT]
>>>
>>> ******************************
>>> http://www.asajay.com
>>> http://www.teampanteraracing.com
>>>
>>>
>>>
>>>
>>> Chris Difani wrote:
>>> > AJ:
>>> >
>>> > Do you want me to ship my vacuum radiator filling device to you?  It
>>> > uses shop air to generate a vacuum, it applies that vacuum to your
>>> > cooling system.  Then it uses that evacuated cooling system 'suction'
>>> > to fill the system with your coolant.  It's got a suction tube that
>>> > drops into your coolant container.  It's also supposed to 'dissolve'
>>> > air bubbles, etc., in the system.  Then you'd only have the thermostat
>>> > to worry about.
>>> >
>>> > If you want me to ship it, give me your address, and I'll get it out
>>> > Thursday afternoon.
>>> >
>>> > This is the Harbor Freight system that we discussed on the list a
>>> > month or two ago... or was it three months??
>>> >
>>> > The only requirement is you need a shop air compressor.  About a 2
>>> > horsepower size.
>>> >
>>> > Let me know,
>>> >
>>> > Chris
>>> >
>>> > Chris Difani
>>> > '73 L #5829 "LITNNG"
>>> > The Electric Pantera
>>> > Sacramento, CA
>>> > Email: cdifani at comcast.net
>>> >
>>> > _________________________________________________
>>> >
>>> > ----- Original Message ----- From: <asajay at asajay.com>
>>> > To: <detomaso at realbig.com>
>>> > Sent: Wednesday, September 02, 2009 9:02 AM
>>> > Subject: Re: [DeTomaso] head drilling for air release
>>> >
>>> >
>>> >> I'm still flustered with that whole idea.
>>> >>
>>> >> I have a 351C installed in my Mach I.  I've never had any problems
>>> >> bleeding air from the system, getting it full of coolant, etc.  It
>>> >> doesn't have air bleeds at the back of the heads.  So doing a bit of
>>> >> Kepner-Tregoe analysis on this, what are the similarities and
>>> >> differences.
>>> >>
>>> >> The engine in the Mach I tilts in such a way the front of the engine
>>> >> is slightly higher than the back (I think), but in the Pantera, it's
>>> >> just the opposite.  So in the Pantera, I can see air getting trapped
>>> >> at the back of the head, but if you've managed to bleed the system
>>> >> properly, are they really necessary?
>>> >>
>>> >> Which makes me wonder why I would want to jack up the -back- of the
>>> >> car, when it seems to me I should be jacking up the -front-.  But 
>>> >> then
>>> >> there is the radiator up front which could trap air.  In my case, I
>>> >> know the radiator was full, as I had a sight-hose connected to the
>>> >> upper corner to verify it was full.
>>> >>
>>> >> My brain hurts.
>>> >>
>>> >> Asa Jay
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >> Quoting Larry Finch <fresnofinches at aol.com>:
>>> >>
>>> >>> Is drilling the heads for air release, as Sean just wrote about,
>>> >>> something that could be done with them installed in a running car, 
>>> >>> as
>>> >>> opposed to something only done with heads off?
>>> >>>
>>> >>> I imagined drill shavings and thread-tapping shavings could easily 
>>> >>> be
>>> >>> an issue.  But I intend to replace my radiator this Winter, so 
>>> >>> having
>>> >>> shavings lodge in this current radiator is not really an issue.  And 
>>> >>> I
>>> >>> also currently have a Tefba coolant filter in place; its purpose 
>>> >>> being
>>> >>> to trap any free flowing trash prior to the new radiator install.
>>> >>>
>>> >>> I'm thinking now would be a good time to get those air bleed holes
>>> >>> installed in my engine?
>>> >>>
>>> >>> Larry
>>> >>> _______________________________________________
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>>
>>
>> --
>>
>>
>>
>>
>>
>>
>>
>> Michael L. Shortt
>> Savannah, Georgia
>> www.michaelshortt.com
>> michael at michaelshortt.com
>> 912-232-9390
>>
>>
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