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Sometimes I feel I'm in a forum where the aim is to come to the most complex solution to any problem... Eeker

And I know many have opinions about this, and if Tajon has enough time and money and wants to try this out, it's a free world, sort of...

But I'd hate other readers with perhaps cooling issues to think this is the needed way to go. The standard Pantera cooling system is OK with very few modifications. Case in point, my own Pantera, 600HP, driven around France in 30+C, gone straight from highway speed to city queue, A/C on: No cooling problems ever.

So here are the requirements for those who would like to know:
WAD (=Working As Designed):
-No leaks, no air pockets. Test with test gauge, must hold pressure for an hour
-All hoses double clamped
-All hoses/tubes clean inside
-Proper Cleveland thermostat, nothing else
-Normal Weiand or similar water pump
-DO NOT move your A/C radiator up in front of engine radiator
Upgrades:
-Replace small inefficient pusher fans with bigger modern puller fans behind radiator

It works.

I have one fan on a thermostat switch and one on a button on the instrument panel. Works like a charm. The thermostat turns on a fan rarely, mostly if standing still after freeway speed on hot day. The button is just used by me for feeling secure, don't think I've needed that #2 fan yet.
Tajon, I authored the article and have enhanced the cooling capacity of many Panteras. If you have specific questions, I'd be happy to help. If you are not driving your car competitively enough to push your oil temps to extremes, a milder approach is adequate. The mod was principally aimed at controlling oil temps from sustained high RPM running on the race track.
John's cooling system mods were detailed in issue 116 of the PI Magazine (fall 2003). Beginning page 48. Back issues are available.

Here's my 2 cents of what is wrong with the cooling system:
  • The OEM cooling system collects air in the radiator.
  • The OEM cooling system flows too little coolant (most problematic at low rpm).
  • The OEM cooling system controls the fans poorly.

Based upon those observations there are a few "basic improvements" to make.

Air management:

Have you ever wondered why the Pantera's coolant recovery tank is over a foot tall and has a pressure cap on it? Its obvious to me by their designs the "system tank" and the "recovery tank" were originally intended to be a "swirl tank" and a "head tank", respectively. Obviously someone realized the need for a "race car style" head tank during the Pantera's design phase. I have found documentation verifying the tanks were indeed altered, but I haven't yet found any documentation explaining "why" the alterations were made.

Alteration of the two coolant system tanks was among the very first modifications made to the Pantera when Ford stepped-in, yet none of the 2 or 3 air removal schemes instituted by Ford were successful at removing air from the radiator. I assume once Ford's engineers altered the tanks budgetary concerns (or ego) prevented them from going back to the original design.

The cooling system needs a low pressure place in which to collect air and isolate it from the cooling system ... i.e. it needs a "head tank". The logic of this is obvious and inescapable when the lay-out of the cooling system is viewed from the side, or when the pressure zones within the cooling system are considered. All modern cars have head tanks for trapping air, but back in 1970 this was race car stuff, it would have been an advanced design for a production car in that era. Fortunately it requires only four small revisions to enable the two tanks to perform their originally intended purposes. By doing so air can be bled from the radiator into the lower pressure of the head tank and thus it can be automatically and continuously isolated in the head tank where it does no harm. The head tank also provides an air space for the expansion and contraction of the coolant in lieu of a recovery tank.

Maintaining coolant back-pressure within the engine block aids in preventing air from being released within the engine block. So the OEM location of the thermostat, at the engine's outlet, is the ideal location. Air shall be released downstream of the pressure drop created by the thermostat. With the "system tank" revised to function as a "swirl tank" (aka a de-gas tank) and located immediately downstream of the thermostat as it is, it shall collect the air and channel it to the head tank before the air has a chance to circulate within the cooling system, as all swirl tanks are intended to do.

Everyone who has performed these revisions speaks quite positively about the results.



In lieu of the head tank, a simple drain petcock can be installed in the top of one of the radiator tanks to facilitate manual bleeding of air. Each owner should utilize one scheme or the other.

Coolant flow:

Coolant pumps are centrifugal pumps; such pumps do not have a linear output (i.e. flow) verses speed curve. The pump must rotate at a certain minimum speed in order to reach the point in which increases in speed result in increases in output. Below that speed the pump's output does not increase with increases in speed. The speed at which the pump's output begins increasing varies based upon the resistance to flow (i.e. head) at the pump's outlet. As the resistance to flow increases it requires a higher pump speed in order for the pump to enter that part of it's output verses speed curve in which increases in speed result in increases in flow. The Pump's maximum flow capacity shall also decrease as head increases.

Neither the OEM Ford coolant pump, nor ANY of its replacements, were designed to pump coolant over the distances it must be pumped in the Pantera's mid-engine application. The amount of head in the Pantera's cooling system caused the OEM coolant pump to drop lower in its output verses speed curve. The pump simply doesn't pump enough coolant at idle speed. Considering the nature of centrifugal pumps it should be no surprise that the lay-out of the Pantera's cooling system impinges upon the coolant pump's output, I am surprised this was not predicted by at least one of the engineers involved in the Pantera project.

Coolant pump output can be improved by 3 things:
  • A pump with a different output verses speed curve.
  • Higher rotating speeds for the OEM pump.
  • Less resistance to flow (aka less head).

The average owner can improve flow most easily with a couple of "bolt-on" parts; the SACC 10% overdrive pulley driving the Flow Kooler pump.

PUMP and PULLEY: The idea for the overdrive pulley came from the De Tomaso factory. In an interview Odoardo Govoni revealed that the factory provided him with an overdrive pulley for his Group 4 race car (the most winning Pantera race car ever) circa 1974. The interview is found on page 102 of Philippe Olczyk's book. Owners who have installed the SACC pulley have reported an immediate drop in coolant temperature with no other changes.

The Flow Kooler pump has a machined billet impeller which they claim improves low rpm flow. Pantera owners speak highly of this pump as well.

PORTED VACUUM SWITCH: The Pantera's ignition controls were augmented by DeTomaso with an electric ported vacuum switch (aka the PVS valve) to contend with the overheating issues. The vacuum switch was designed to retard the ignition thereby reducing the engine’s idle speed by 100 to 400 rpm when a predetermined high temperature limit was reached. Retarding the ignition increases the cooling system's heat load, while reducing idle speed also reduces the speed of the coolant pump, thus reducing coolant flow. This response to high coolant temperature was opposite to the way in which Ford’s ignition controls were normally designed to react to high coolant temperature. The electric ported vacuum switch did not alleviate the Pantera's propensity to operate hot during stop and go driving ... it made things worse.

The PVS switch should be disabled and removed from every Pantera in which it was installed. The distributor's vacuum advance connection should be connected directly to the carburetor's "ported vacuum" connection, and the distributor's vacuum retard connection (if so equipped) should be left open to atmosphere.

THERMOSTAT: The thermostat built into the 351C was an advanced design for its day. Ford engineers referred to it as a "controlled bypass" system. It increased the amount of coolant bypassing the radiator during warm-up in order to eliminate hot spots in the cylinder heads during warm-up and to provide faster warm-ups too. Once the engine reached operating temperature the coolant bypassing the radiator was shut-off completely. Similar functionality is accomplished in modern cooling systems with divorced thermostats, but the Ford engineers who designed the 351C accomplished it with an internal thermostat. The OEM "Robertshaw 333" style thermostat was a high flow thermostat as well. I don't believe you can improve upon the OEM thermostat design built into the 351C if the proper parts are utilized.

RADIATOR: When the time comes to replace the radiator, the replacement should be chosen based on core design. Radiators with less restrictive cores (promoting an increase in the coolant flow rate) should be chosen. I like the copper radiator sold by Hall Pantera, it is equipped with a beefy "truck-style" core known to alleviate cooling system problems.

RADIATOR OUTLET PLUMBING: The suction of the 351C coolant pump has a 1-3/4" OD hose connection. The radiator outlet of all Ford's V8 equipped vehicles was also 1-3/4" OD. In the Pantera the plumbing between the radiator outlet and the coolant pump inlet is 1-3/8" OD, which is much too small and constitutes the most severe "resistance to flow" in the cooling system's plumbing. Rubber hoses located on the radiator's outlet plumbing tend to collapse at idle due to the severity of the resistance to flow.

The coolant pump inlet was originally connected to the radiator outlet plumbing via a 90° metal tubing elbow and a 90° rubber hose elbow. The rubber elbow was known to collapse at low engine speeds which severely restricted coolant flow. This plumbing arrangement was replaced in May 1972 by a "double-bend" metal tube which only used a short-straight rubber hose to connect to the pump inlet. According to Ford the new arrangement was made to create more clearance for the shift linkage. Whether it was intentional or accidental the change also improved the cooling system, by reducing or eliminating the collapse of the rubber hose on the pump's suction.

Therefore steps must be taken to prevent the collapse of any rubber hoses on the radiator outlet plumbing. There are three ways to do this including (1) keeping all rubber hoses as short as possible, (2) using stiff-thick wall hose such as "Gates green stripe" hose, or (3) installing something within the hose to prevents it's collapse (such as a piece of 1-3/8" OD stainless steel tubing or the coiled wire from a radiator hose designed for another car).

If you are considering making revisions to the coolant system plumbing then increasing the size of the radiator outlet plumbing to 1-3/4" OD is where to begin your effort. That's equivalent to a 62% increase in cross-sectional area ... no small matter. Given the cooling system problems the Pantera was having I'm sure Ford engineers identified this problem. I assume budgetary or managerial constraints limited how many changes they were allowed to make, and reconfiguration of the radiator baffle was given priority.

Fan control:

Speaking of the radiator baffle, the Pantera's radiator was originally equipped with a vertical baffle. The vertical baffle did not seal well inside the radiator's tank however and it allowed too much coolant to bypass the radiator. Ford reconfigured the baffle in April 1973, replacing the vertical baffle with a horizontal baffle. The Ford engineers were quite right in prioritizing the elimination of this issue, it had been the worst of them. Once the horizontal baffle replaced the vertical baffle a Pantera could idle all day long without over heating, on a hot summer day, with the air conditioning operating.

Reconfiguring the radiator baffle had a detrimental impact upon fan control however! The fan control switches, which had both been originally installed in the radiator's "outlet" tank, ended up being located in two different tanks due to the reconfiguration of the baffle. But Ford did not revise the temp settings of the fan control switches. The fans haven't cycled properly since.

The reason the Pantera is equipped with two cooling fans is due to the rectangular shape of the radiator. If the radiator was "square" it would only have one fan and if there was only one fan nobody would feel the need to control it with more than one temperature switch. Just because there are two fans does not mean they have to be controlled at two different temperatures, there is nothing gained by doing so. Its puzzling why De Tomaso or Ford engineers chose the complication and the expense of two switches over one.

Designing an automatic fan control should have been simple, its something which other cars of that era did quite successfully with one fan switch. Owners of other cars equipped with electric fans took fan operation for granted, Pantera owners should have been able to do the same. Consider the two fans as a "fan system" and control that fan system with a single fan switch. The switch should be mounted in the radiator's inlet tank, set at a temperature which complements the setting of the thermostat. The fans will cycle on and off automatically as needed if a switch set to control at the proper temperature is chosen. If the fans run all the time then the cooling system is running too hot, or the wrong switch was chosen.

Switch Manufacturer...Part Number.........Switch Setting in °C........Thermostat
Intermotor.................50104..................97°/92° ........................192°F or 195°F
Intermotor.................50200..................92°/87° ........................180°F
Wahler......................823.959.481.F ......92°/87° ........................180°F

Notice there is no mention of high flow fans. This is not an oversight, its intentional. High flow fans are a Band-Aid fix, they may help a marginal cooling system but they don't address the core problem. Coolant flow is the real issue, not air flow. Of course, folks who operate their Panteras in truly hot climates (like Arizona) can make good use of those high-flow fans.
Last edited by George P
My observation and opinions are the same as George's above post.

However I see one other MAJOR concern that is actually an accumulation of the above points and is mitigated by the proposed improvements. For there to be flow, there MUST be a pressure gradient. As George stated, a “normal” car coolant system does not require a lot of pressure to achieve flow, but with the Pantera’s distances a pump that can develop pressure is needed. I have yet to find online anyone that has ever determined the pressure/flow for a Pantera. I have seen other similar vehicle discussions where 15 PSID is mentioned. Now, with the Pantera’s coolant pressure cap on the swirl tank, inlet to the radiator, this SETS the maximum pressure gradiant for flow. The pump suction at the impeller being the lowest pressure in the system can be expected to be LESS than normal atmospheric AND this would cause warm coolant to flash to steam very much below the 212F associated with boiling. This being called cavitations and causing the pump to no longer develop any pressure as steam cannot be pumped. It doesn’t need to be 100% cavitations, but a very small % will greatly reduce the pumps output
Convert the recovery tank into a head tank
(1) Add a tube fitting or nipple to the recovery tank for the bleed from the radiator.
(2) Add a tube fitting or nipple to the recovery tank for the bleed from the system tank.
(3) Increase the size of recovery tank's bottom fitting to 1/2".
(4) Screw a fitting into one of the threaded ports on the side of the coolant pump, 3/8" NPT to 1/2" hose.
(5) Connect the top bleed of the radiator to its new tube fitting or nipple on the recovery tank with hose.
(6) Connect the bottom fitting of the recovery tank to the new fitting on the coolant pump with hose.
(7) Install the 13 psi radiator cap from the system tank onto the radiator cap fitting of the recovery tank.
(8) Raise the height of the recovery tank within the clamp that holds it.
(9) The recovery tank is now a head tank.

Convert the "system tank" into a swirl tank:
(1) Remove the radiator cap fitting from the system tank, block the remaining hole.
(2) Flip the system tank over and add a tube fitting or nipple to the middle of the "top".
(3) Connect the new tube fitting or nipple of the recovery tank to its new tube fitting or nipple on the head tank with hose.
(4) The system tank is now a functional swirl tank.


•Use 1/4" hose for the radiator vent and swirl tank vent
•Use 1/2" hose to connect the "header tank" to the coolant pump suction
•The Flow Kooler coolant pump (and others) have two 3/8" NPT ports that can serve as the connection to the head tank
•The head tank should be clamped in the mounting strap at a height making its mid-point approximately the same height as the highest point in the coolant system. I assume the highest point is the top of the "system tank" aka "swirl tank". Cutting a hole in the cover above the head tank, the same as the OEM hole found in the 1974 models, makes this easier to live with, because the pressure cap on top of the head tank will be accessible through the hole. Cutting the hole in older Panteras is covered in TSB 11, page 3.
•When filling the coolant system, it is best to "top-off" the cooling system when it is hot but with the pressure cap removed (zero pressure on the pump suction), under those conditions the coolant level in the header tank should be no more than half full.

This is also covered in my post on the first page of sticky #2 and other posts.

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Last edited by George P
quote:
Originally posted by tajon:

Would like to see the one tank method.


If I wanted a one tank system,

I would cut the pipe from the thermostat to the swirl tank so just to have the elbow.

I would then cut the pipe from the swirl to the lower tubes and turn it to connect with the thermostat pipe. use a hose between the two

in the thermostat elbow, install a high vent and hose it to the longer tank (about mid way)
connect the tank bottom to the water pump suction and put a pressure cap on the tank

the tank needs to have its mid level at the same level as the thermostat elbow

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quote:
Or.......

You could keep the stock system design, perform normal maintenance, replace failing components with quality replacements and somehow still manage to have a perfectly functional system that gives fine performance year after year..... just as hundreds and hundreds of Pantera owners are still doing.

Larry


Larry for President! But Larry you forget, most of us in here consider ourselves wiser than the factory
Hi..all nice discussion, not there in my rebuild but close (need some welding on the Fluidine Radiator (2 outlets on right side) posts on the cross bar first).

for now 2 questions:
quote:
if you are considering making revisions to the coolant system plumbing then increasing the size of the radiator outlet plumbing to 1-3/4" OD is where to begin your effort.


1) Well in my case the tubes below are today aluminium 35 mm = 1 3/8 ". so where is the cross over from 1 3/4 to 1 3/8 then?
(guess at the pump tubing/Rubber..?)

and...

2) the picture from the sticky and in the note indicates to me the HOT side of Water (comming from swirl Tank) goes into the lower portion of the radiator.?? - My older Fluidine has kind of 2 horizonal layers the fluid needs to go through.
- Hot Water on top outlet or lower outlet? Top down or bottom up..
(I understand hydrodymanics, ..hot water moves up..smile)
- THEN the Thermo switch needs on the HOT side (assume now lower side?)
.......just to confirm...

sorry was not clear to me..
TX
Matthias
quote:


Originally posted by "72 GTS:

... I'll fit 180°headers, and then need to relocate the tank ... I read somewhere that I would only need one tank ...



Without a head tank you need two tanks, one for the pressure cap and a recovery tank to catch the hot coolant which is relieved from the system as it expands.

A head tank is equipped with a pressure cap, it serves as the fill point AND the air space within the head tank allows for the expansion of the coolant as it heats up. A recovery tank is not required, therefore you can truly have a one tank system.

So if I were revising the cooling system to have only one tank, I would convert the recovery tank to a head tank, and eliminate the swirl tank.

quote:


Originally posted by Mat_G:

... where is the cross over from 1 3/4 to 1 3/8 then ...



Increase the size of the radiator outlet nipple to 1-3/4" (45mm). The coolant pump inlet is already 1-3/4" (45mm). The size of all of the plumbing between should then be increased to 1-3/4" (45mm).

quote:


Originally posted by Mat_G:

... THEN the Thermo switch needs on the HOT side (assume now lower side) ...



Yes, correct.

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