Mr. Dick Ruzzin, the owner of the Chevrolet powered Mangusta built to special order for William L. Mitchell, VP in charge of styling at General Motors. Mr. Ruzzin, a former GM stylist has honored us with the following information for Mangusta Owners. Thank you Dick!
MANGUSTA COOLING IMPROVEMENTS / Dick Ruzzin 5-10-2006
This might help some Pantera folks too, or anyone trying to make a car cool. This isn't scientific but it works. A small spoiler and sealing off a radiator was always guaranteed to produced positive results during my many windtunnel adventures. The important thing to remember is that the cooling system is just that, a system. You have to address every component and optimize each one.
Last year I had an aluminum cross-flow radiator made for my car. It has two rows of 1" tubes and is about 2 3/4 inches thick. Previously I had tried many tricks to improve cooling with my original brass radiator, but nothing really made a significant cooling improvement. My car was often on the ragged edge of overheating and it boiled vigorously countless of times, once even bursting the header tank.
The shop that made the radiator checked the coolant flow from my new heavy duty water pump, which was good, but found that my gauge was not correct. It showed that the engine was running hotter than it really was at low temp readings and hotter than it really was at high temp readings. This discovery was important because the gauge was not displaying the new radiators capability properly.
They assured me that from their experience, which is substantial, the engine had the right type and size radiator and that it would cool. The engine is a Chevrolet 350 CI smallblock.
I luckily matched a new sending unit with my temperature gauge on the first try and verified the temperature in the engine, header tank and radiator with both a laser temperature sensor and my wife's cooking thermometer. I found that the hottest part of the cooling system was the gooseneck above the thermostat. My temperature sending unit is close to that, in the intake manifold.
In the past I had applied the classic windtunnel steps, but now I realize that my old radiator did not have the capability to cool the engine to the desired level either at speed or idling in traffic. No matter what I did it could not keep the engine temperature as low as I wanted it to be. Granted that my idea of ‘cool’ is old fashioned compared to todays cars.
I have now done all of the following, including the new radiator, with great results:
Picture/ 1969 Detomaso Mangusta
I added a small spoiler, 3/4 of an inch lower than the underbody, applied just at the bottom of the front end and slightly behind the bottom of the radiator. This causes a vacuum at the back of the radiator, helping to draw air through. I made a nice little 1/4 thick ABS spoiler that is pop-riveted to a 3/4 inch
steel angle. The angle is attached to the two front stub rails by hinges and two small screws so that it can be quickly removed.
This small spoiler, 2 5/8 inches vertically (60mm), is enough to make the front end very stable at high speed. The car feels solid with no feeling of lift at 80 mph. Increasing the vertical dimension may lower the overall drag but as the spoiler gets closer to the ground you will have a ramp angle problem. The new spoiler is 4 1/2 inches off the ground, (114 mm).
SEAL OFF THE RADIATOR
Seal off the radiator, bottom, sides and top so that all air that is not going around the car has to go through the radiator. Like the spoiler, this also helps to stop cooled air that is still hotter than the ambient temperature, from recirculating from the back of the radiator to the front again when you are stopped. Make sure you remove the panel above the radiator in the luggage compartment and seal the top of the radiator against it with foam insulation so that air cannot go over the radiator. Seal every nook and cranny using waterpipe insulation foam.
I have two 25 amp puller fans and a shroud. I used two inch wide adhesive aluminum foil tape from Home Depot to seal my shroud to the radiator.
I calculated that the shroud had gaps that totaled over 3 square inches of
The engine now has a heavy duty Chevrolet water pump. I put the pump in because I am guessing that the original stock 1969 Chevrolet waterpump was not designed to push coolant from the back to the front of a mid-engine car. In a Camaro or Corvette it went less than 12 inches.
I started with a 160 degree thermostat and modified it for more flow by removing some metal from the three fingers that hold the center core to the outside ring. Also, 1/8 of an inch is cut off of the skirt so that it is always open by 1/8 of an inch. I will change to a standard 180 since I now have a system that really cools.
COOLANT RECOVERY SYSTEM
I have a coolant recovery system with the top rubber seal on the 18 pound cap sealed to the header tank with silicone seal to assure a vacuum in the system. This makes coolant movement from the header tank to the coolant recovery container positive with no air leaks. This keeps the system completely full of coolant. This is very important.
CLOSE OFF FRONT END LOWER OPENINGS
This seems to be the opposite of what should work. Tape over the eight 2 1/2 diameter holes in the lower valance sheetmetal on the bottom of the front end. These holes are just behind the bottom of the radiator. They were probably put there to reduce lift, the little spoiler now does that. Covering the holes caused a greater vacuum behind the radiator. Since the holes are behind the radiator I think they forced air into the area behind the radiator that competed for space with the air trying to come through it, diminishing the air flow. They also allow hot air exiting the radiator to curl around to the front of the car and re enter the cooling air stream.
The new radiator made a huge difference but in the last week I have finally, with warm weather, had a chance to add the seals and to tape up the holes.
Following is my experience.
ADDING THE SEALS
First I added the seals and was amazed. I used that gray waterpipe insulation that comes in about four diameters. It is flexible and easy to work with, it is easily packed around the radiator to seal it off. The car ran with the thermostat just opening slightly, and on my traffic run I saw almost 190 degrees at traffic lights, with the temp slowly going down to 160 once I started moving. I had to use the fans before to move the temp down after sitting at the same two traffic lights.
TAPING UP THE FRONT END OPENINGS
Next I taped up the openings with clear packing tape and went for another ride, same outside temperature, same route. Another big cooling improvement, this time the thermostat did not open at all, the little 1/8 gap that I cut off of the skirt of the thermostat is passing enough coolant to cool the car when running. The temperature has been 72 degrees for all of these tests. (I have now removed the tape and blocked the holes with some thin black aluminum discs that have been attached to the inside of the panel.)
At the traffic lights the gauge needle hardly moved and the temperature dropped rapidly when I moved on at steady speed. This radiator has cooling capacity far beyond the original. I did not use the fans.
I now feel confident enough to go on some parts of the Woodward cruise!!!!
My final step is to install an adjustable temperature sensor to turn the fans on and off automatically. I still will also be able to do it with the switch on the panel.
>>>>See the article that I have written specifically on that subject.<<<<
The fans are 25 amps each so I used a 50 amp circuit breaker and 10 gauge wire with heavy duty wire hardware. The fans are now running noticeably louder and seem to push much more air.
Hopefully some of this will help someone who is struggling to make a car cool.
All the best, Dick Ruzzin.