[Healeys] Overheating

Sun Mar 7 15:22:58 MST 2021

Like many of you I have been cooped up for the past 12 months waiting for a
vaccine and for life to return to normal. I have been happily occupying my
time doing a complete restoration of a BT7 and had lots of time to consider
what upgrades or modifications are recommended to overcome some of inherent
Healey problems. I come to realize maintaining a consistent temperature of
the cooling water is an issue. With little else to do while in lock down I
looked into the factors that affect cooling to see if it would point to any
obvious upgrades. The design of automobile cooling systems is very
complicated but can be distilled down to a few key factors. Identifying the
factors that have the greatest influence on the system will help to point to
possible solutions or remedies. I will suggest some of the factors may not
be as obvious as others.

The job of the cooling system is to remove the engine heat generated. If the
capacity of the cooling system to remove heat (i.e. BTU's or HP) is greater
than the engine heat generated in all situations then the system will reach
a steady state. For most Healey's driving on flat road at 60 MPH when
ambient temperature is less than 80 F everything is in balance. For many
Healey's the situation changes at lower engine RPM's and vehicle speeds.
What are the critical variables that affect the water temperature the
thermostat sees:

1. Engine heat generated.
2. Radiator heat transfer coefficient.
3. Air temperature or more importantly the difference between air
temperature and the radiator cooling fin temperature.
4. Water flow rate.

At slower engine/vehicle speeds hotter air from the engine bay can surround
the radiator and the water flow rate drops. We can estimate the influence of
each:

If the air temperature at the radiator core increases from 80 to 100 deg F
the water temperature will increase approximately 20 deg F. All things being
equal the water temperature will increase approximately 1 deg F per degree
increase in air temperature.
If the water flow rate decreases by 20% the water temperature at the top of
radiator will increase slightly and will drop slightly at bottom of the
radiator.

If the water temperature was above the full open temperate of the thermostat
when driving at 60 MPH then the thermostat is no longer controlling the
system and the water temperature will change when one of the critical
variables changes. Often the conclusion is changing thermostats, fans or
using some exotic coolant. I will risk the wrath of this forum and suggest
one of the clues to solving the slow speed problem is look at what is
happening at 60 MPH. If the water temperature is above the thermostat rating
while driving at highway speeds then factors 1 and 2 above are likely the
issue. In other words there is no reserve capacity in the cooling system and
soon as air next to the core gets hotter the water temperature increases.

The engine heat generated is a major factor, the less heat the marginal
Healey cooling system has to deal with the better. If the engine heat
generated can be reduced by 20% the water temperature will decrease by 22
deg F. The factors that affect engine heat generated are: losses due to
friction, air/fuel mixture and engine timing. If the air/fuel mixture is too
lean it will cause the engine to generate more heat. A fuel pump that
maintains the minimum required fuel pressure at all engine speeds and well
tuned and jetted carburetors are important. The correct ignition timing and
the mechanical and vacuum advance curves are very important to reduce heat
generated.

Lastly we have the radiator heat transfer coefficient. The coefficient is
based on the design of the radiator, number of tubes, rows of tubes, type of
fins, density of fins, area of radiator, materials used to construct the
radiator, etc. The units are BTU/hr/deg F. If some radiator tubes are block
or have reduced flow, if the fins are damaged or fowled with debris, if the
radiator has cracks or spilt seams or if the radiator top tank is not full
the radiator will not perform at its optimum. If in doubt have a radiator
shop boil out the radiator and pressure test.

It seems some Healey's don't have a problem with over heating while others
do. One possible explanation is the Healey cooling system is marginal at
best and all of the factors that could affect overheating must be in harmony
with little room for forgiveness.

The upgrades I have done are a plastic 5 bladed fan, new stock radiator
core, 123 ignition and bungs on the exhaust for oxygen sensors. Time will
tell if these helped tame the cooling system.

I hope this helps and isn't killing a fly with an elephant gun.

Harold

  _____  

From: Healeys [mailto:healeys-bounces at autox.team.net] On Behalf Of Leonard
Berkowitz via Healeys
Sent: Sunday, March 07, 2021 7:08 AM
To: healeys at autox.team.net
Subject: Re: [Healeys] Overheating

So first step is to make sure your temperature gauge is accurate. If you are
still running hot I solved the problem by adding an additional row to a
factory original radiator.  Haven't had any problem with overheating since.
I had already tried adding an electric fan, an oil cooler and a Texas fan.
Nothing worked. 

  _____  

From: Healeys <healeys-bounces at autox.team.net> on behalf of
rfbegani at gmail.com <rfbegani at gmail.com>
Sent: Saturday, March 6, 2021 4:58 PM
To: 'Michael Salter' <michaelsalter at gmail.com>; 'Bob Spidell'
<bspidell at comcast.net>; 'Ahealey help' <healeys at autox.team.net>
Subject: [Healeys] Overheating 

Bob & Mike:

You both may have seen my requests on overheating of my BJ8 and the response
from the group.  As a result, I purchased an infrared thermometer to
determine if my water gauge was giving accurate readings.  The thermometer
gun told me that my water gauge was 30 degrees higher than the temperature
of the sensor attached to the block.  At the same time, I noticed my gauge
will show 120 degrees at rest instead of going down to 90 degrees which
would indicate a 30-degree high reading.  In May when I leave for cool
Michigan, I will send the gauge to Nisonger to be rebuilt.

I began to test the temperature of the water going through the cooling
system at the inlet to and outlet from the block, inlet and outlet to the
radiator and the upper and lower hoses while the engine is running at idle
and at 2-3 Thousand rpm.  The chart I created to record these temperatures
allowed me to produce observations or averages because the flow of the water
is dependent upon the rpms of the engine.  The engine has overheated all of
the 40 years I have owned it and has only 1000 miles on the new speedo since
rebuilding to 20 over. 

At the radiator inlet 134 outlet 85 at high rpms with electric fan
operating.

                        inlet 103 outlet 94 at idle rpms with electric fan
operating. 

The above temperatures are recorded at the inlet and all along the hoses.

These temperatures indicate the pump is circulating water with sufficient
gallons to cool the engine only when the engine is at high rpms.  At idle
the pump does not circulate sufficient water to keep the engine cool.  This
is especially true when you have been operating the engine at high speed and
come down to 30 - 40 mph and stop and go traffic.  Maybe the real answer is
to install an electric pump for constant cooling water?

In the past week, I have installed a large Dorman coolant recovery tank and
a new 7 psi 1 inch radiator cap because I learned that our radiators have a
long neck.  Both those changes have reduced my problem of very high
overheating and resulting boiling over.  In addition, when my water gauge
shows 212 degrees the water temperature is actually 30 degrees less or
approximately 185 degrees.  Also, I am not boiling over and loosing coolant.
Nevertheless, the engine water temperature is still spiking to 210 plus
degrees true when coming off highway speeds.  

In my review of various sites, the radiator equipment suppliers and others
are recommending increasing the pressure in the classic car systems to 15
psi plus, and coolant recovery tanks "if your coolant system, radiator,
hoses etc. is new" and therefore can hold the pressure.  Unfortunately, I
have not found any maker of a 1 inch depth x 2.33 inch diameter radiator cap
except our 7 psi cap so I can try such a pressurized system.

Another suggestion on an older discussion at the British Car Forum indicated
some of the Ontario car owners had switched to Evans Waterless Coolant
rather than 50/50 coolant water mixture.

I still have no idea why a minority of our group has overheating problems.
More ideas?

Regards,

Bob Begani 67 BJ8 

From: Healeys <healeys-bounces at autox.team.net> On Behalf Of Michael Salter
via Healeys
Sent: Saturday, March 6, 2021 12:20 PM
To: Bob Spidell <bspidell at comcast.net>
Cc: healeys at autox.team.net
Subject: Re: [Healeys] 100 water pumps

Yes Bob, there is something wrong with our assumptions regarding the cooling
system not being "large" enough. 

My wifes Maxima is around 300 HP and the radiator has less area than the
100. Certainly it has a couple of very effective electric fans but they
really don't cut in very often unless you have the AC on.

I'm suspicious of the rate of circulation but I've talked to Larry Varley
about this subject and he indicated that increasing the size of the water
pump annular orifice didn't make much difference when he tried it.

M

M

On Sat, Mar 6, 2021 at 11:42 AM Bob Spidell <bspidell at comcast.net> wrote:

I sold my late father's 1955 Thunderbird to my BFF. These cars have a very
similar problem to Healeys overheating, esp. at idle. When Ford stuffed the
292ci Y-Block into the T-Bird, they found the engine was (essentially) too
short for the long-hooded car, so they 'engineered'--I use the term
loosely--a cast iron spacer to move the fan closer to the radiator. The
spacer had the added 'benefit' of severely limiting coolant flow through the
pump and radiator; there are some aftermarket fixes and my friend, after
doing the usual radiator re-core, better fan, etc. installed both a better
pump (larger vanes) and a re-engineered spacer. Attached pic is not of the
spacer he used--I can't find the link to it--but it shows the general idea
(Ford basically put a 'dam' in the cooling system to block flow, and the
improved spacers mostly remove it). It appears this approach has improved
cooling, though the engine probably still gets warm if it has to sit too
long at idle. Link is to one of the improved pumps:

https://www.classictbird.com/Water-Pump-Modified-for-Higher-Output-1-Per-car
/productinfo/8501HO/

Anyways, after doing all the usual stuff to increase cooling, esp. on my
BJ8, I've wondered if a similar approach would work on Healeys. Their pumps
have very small vanes, and the cavity in which the vanes operate seems
pretty small for such a large lump of cast iron (I'm guessing an uprated
radiator core won't help much if the coolant flow is still hampered; at
least, that's what I've found). This is probably not an option as, of
course, our engines don't have a similar spacer to be improved upon, and it
would be a major task to increase both the cavity's size and the pump (but I
can dream).

ps. The overheating issue with Healeys is usually attributed to too big of
an engine in too small of an engine compartment, and too little airflow.
But, the engine bay in an old T-Bird is huge by comparison--and the engine
not terribly larger in displacement--and still suffers the same problem.

Bob 

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