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Reply to "cooling system advice ??..."

Paul,

The OEM cooling system was a botched job, if I were to explain it to you you'd either assume I was full of bull or somebody at DeTomaso mistakenly assigned the janitor to design the cooling system. On top of that the 351C was designed with a unique thermostat that over time has always been replaced with the wrong thermostat (i.e. a Windsor thermostat), resulting in over heating every time.

The aftermarket replacement equipment available for the Pantera cooling system duplicates the original "wrong" engineering. There are two ways you can choose to go: (1) engineer the cooling system properly which requires custom fabricated equipment, or (2) use what is readily available and make the best of it.

The goals for improving the cooling capacity of the cooling system are:

1. employ the correct thermostat
2. increase coolant flow through the system
3. increase the surface area of the radiator
4. decrease the radiators restriction to air flow
5. decrease the radiators restriction to coolant flow
6. increase the air flow capacity of the electric cooling fans
7. fix the system's inoperative air bleeds

I'm going to assume you do not want to re-engineer the cooling system, few owners do. The two most prevalent replacement radiators (Fluidyne & Ron Davis) effectively deal with goals 3 & 4. I've seen many Panteras in which the original cooling pipes were partially or fully plugged with rust, so replacement with a stainless pipe kit is highly recommended to help with goal 2. The dual Flex-a-lite fans that are so commonly recommended flow about 2500 cfm, which is very good, effectively resolving goal 6. The Edelbrock coolant pump is rated at 35 gpm and is the best of the usual choices, it will hopefully improve coolant flow (goal 2). As a side note, Larry Stock sells a racing coolant pump rated at over 100 gpm (manufactured by EMP/Stewart Components); the pump is designed for Windsor motors but Larry performs the modifications needed to allow it to fit a 351C. Many people cringe at the price of the Edelbrock pump, Larry's pump is even more expensive.

This brings me to the two tanks, the swirl tank and the overflow tank. The original tanks rust internally and get thin over time, eventually a hole in one of the tanks will develop, so replacement of the tanks is recommended. Now here's the head slapper. The purpose of a swirl tank is to remove air from the coolant, any air collected by the swirl tank must be vented. Swirl tanks do not normally have radiator caps on them, a radiator cap doesn't allow air to vent, it defeats the purpose of the swirl tank. In other words, the Pantera swirl tank is non-functional. There is normally an air bleed at the high point in the swirl tank where air collects. That air bleed would be connected to a "surge tank" (also called an expansion tank) which is the low pressure point for the cooling system. Now take a look at the "overflow tank". It also has a radiator cap, overflow tanks are normally vented to atmosphere not pressurized, there is no need for a radiator cap on an overflow tank. The Pantera's overflow tank was originally intended to be a surge tank! I state that with 100% certainty because all cooling systems employing a swirl tank, or any type of air bleed, also employ a surge tank. Surge tanks are the normal place to route air bleeds because they are the low pressure point in the cooling system. The Pantera has no proper place to route air bleeds because its surge tank was mistakenly used as an overflow tank by an inexperienced engineer! The radiator's air bleed in the Pantera is connected to the swirl tank, which is a higher pressure point than the radiator outlet, its not possible for air in the radiator to vent into the swirl tank, the coolant will actually flow in the opposite direction. Air is supposed to be vented away from the swirl tank, not into it! It does no good to remove air from the coolant with air bleeds or a swirl tank if you have nowhere to vent that air to! This is why I am certain the overflow tank was originally intended to be a surge tank.

Even if you do no further re-engineering of the coolant system, I recommend you make some small modifications to your 2 new tanks which shall allow the tanks to be used as originally intended, as they would normally be used in a cooling system employing a swirl tank. Remove the radiator cap fitting on top of the swirl tank, cap the tank off with a plate (requires welding) and install an air bleed at the high point. Then install 2 connections for air bleeds in the overflow tank.

In your re-engineered system, the bottom nipple of the surge tank (former overflow tank) shall be connected to the suction of the coolant pump. The Edelbrock coolant pump has a spare pipe threaded connection that can be used for this purpose. This tank will be run about half full of coolant, an air space shall be maintained in the tank to compensate for the condensing & expansion of coolant as the system temperatures vary. There is no need for an overflow tank in a cooling system employing a surge tank. The new air bleed on top of the swirl tank will be connected to one of the 2 air bleed connections on the surge tank. The air bleed connection on the radiator outlet tank shall be connected to the other air bleed connection on the surge tank. This small re-engineering of the coolant tanks resolves goal #7 and fixes one of the design errors of the Pantera's cooling system.

Finally, if you are employing a 351C as your Pantera's motor, you need a Robertshaw 333-180 thermostat. Your thermostat should look like the thermostat in the picture below. If it doesn't, buy the correct thermostat and install it. Take the other thermostat back to the guy who sold it to you and tell him George said he should shove it up his ...... Smiler Goal #1 resolved.

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Last edited by George P
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