Cooling System


Keeping the beast running cool has been a real challenge. Where I live it is not unusual for the temperature to be in the mid to high 90s during the summer, with a 500 horse power engine and minimal room for a radiator, I needed to do everything possible to keep it running cool on the street. After a lot of trial and error, it is consistently running at 210 to 220, just perfect.

We all know that the water pump can’t pump steam, steam also creates cavities in the block and head resulting in overheating. Everything we do, therefore needs to insure that the coolant stays in a liquid form. Most high performance engines run well at 220, If the coolant turns to steam too early, the car will overheat at 230 degrees or so, which leaves little room for an extended stop at a traffic light on a hot summer day. So there are two objectives to keep in mind. We would like to keep it running in the range of 220 and at the same time raise the boiling point.


Use as big a radiator as you can, mine is a 4 row big tube 11” by 25” cross flow that I had custom built for around $350.00. I would have loved to use something bigger but there simply was no additional room. To make matters worse the radiator is about 6” lower than the water neck on the intake manifold, this results in the inability to purge air from the system unless a filler is located at the highest point.

Fans and Shroud

Because of space there was no way for me to use a mechanical fan so I use electric fans, the additional benefit is more horsepower. I designed a shroud around the radiator that allows maximum airflow in the grill to pass through the radiator, no air escapes. I used one Perma-Cool 14” high flow (2950 cfm) pusher fan in the front and a smaller 10” puller (950 cfm) fan in the back. Originally I had two 10” pushers in the front, while it looked cool, it didn’t “cool” very well. Go with the highest cfm fan that you can fit, the shroud will force the air to all corners of the radiator. Also, make sure to use a relay, there are two reasons for this, fans pull a lot of amps, my two fans pull 17 amps, this can fry your wires and switches. By using a relay, right at the fan (not under your dash) you do not experience voltage-robbing resistance between the relay and the fan. I recommend supplying the power to the relay directly from the alternator instead of going to the fuse box. This saves wire, resulting in a cleaner installation but most importantly it reduces resistance and insures that your fans are receiving the maximum available voltage, a drop of say one volt can slow the fans down enough to make a noticeable difference in cooling.


Because the radiator is lower than the manifold water neck I did not have a filler neck put on the radiator. Instead I had a custom water neck made with a 4” rise that fits inline in the upper radiator hose, the water neck is polished aluminum, sits right beside the blower belt and looks good. This is not optimal but it works (because of the 4” rise), ideally the filler neck should be in the low-pressure side of the radiator, not on the high-pressure side where the water pump and upper radiator hose are. To close the system, I added an aerospace components recalculating catch can, this is a polished billet aluminum unit with a one pint capacity. I mounted it in the left fender well out of the way and near the ground so if there happens to be any run off, it won’t spray all over the engine and make a mess. I am using a one-pint capacity, because of space, but would recommend a one-quart unit if you have the room.

Radiator Cap

I use a 24 pound radiator cap by Moroso. Your radiator cap is a fusible link for your cooling system, too much pressure and the cap opens to let some pressure escape. However water boils at a higher temperature under pressure so your system will stay cooler with a higher pressure cap. Most systems are made to run 12 to 18 pounds and a 24 pound cap will blow most stock systems apart, so don’t try this unless you are using a high pressure radiator built to withstand that kind of pressure.


Many people believe a 50/50 coolant mix is optimal, and that is certainly what we are taught about cooling system maintenance of stock vehicles. A 50/50 mix does help to raise the boiling point a little, and is certainly necessary in freezing weather, however it is ineffective for high performance engines in hot climate. Studies have shown that 100% water cools better (but at a lower boiling point) than a 50/50 coolant mix, if you want to raise the boiling point, go with a higher pressure system and run a 90/10 mix. 100% water doesn’t do a good job fighting rust and corrosion so I use a mix of 10% coolant and 90% water. Use a cooling system lubricant and anti rust agent to help fight corrosion instead of antifreeze.

Transmission and oil cooler

Adding a transmission and oil cooler doesn’t directly effect the engine temperature, but it does help keep the vital fluids cool and therefore saves seals and bearings, which do not respond well to extreme temperature. You want to keep your transmission fluid between 160 and 200 degrees. If you run your transmission fluid through your radiator as a means to cool it and if your radiator is keeping your water temperature at 220, you will be overheating your transmission fluid, technically speaking this is not a good thing to do.

I use a B&M polished aluminum transmission cooler (11”x4”x1˝ ”) I selected a small cooler because of the car’s light weight and limited space. I mounted the cooler under the transmission pan, so the plumbing is minimized, it fits nice and neat between the frame rails and gets a cool stream of air passing over the fins from under the car.

To cool the oil, I selected a Perma-Cool aluminum oil cooler rated for 450 hp (21x7x1˝”). I mounted the oil cooler under the car below the oil pan. Like the transmission cooler, I did this for three reasons, to optimize limited space, to minimize plumbing and to get a flow of air passing from underneath the car.


Don’t waste your money on chemicals that claim to make your car run 20 to 40 degrees lower, they don’t work, period. Also do not remove your thermostat, this can increase your flow and it won’t have enough time in the radiator to cool down. In the old days we used big flat washers in the thermostat housing to restrict flow, the theory is they slow down the time coolant is in your radiator so it will have more time to cool down, sounds logical, right? Wrong! By doing this you are not just slowing down the flow in your radiator, you are also prolonging the time coolant is in your block and head, and this is not good. If your thermostat is not working replace it.

Other factors

There are many other factors that can contribute to overheating including, Inadequate under hood circulation, lean fuel mixture, and improper ignition timing to name a few

It took me a while to get the cooling system dialed in so it wouldn’t run hot, there are a lot of compromises and tradeoffs especially in a small car. You need to consider physical space, cosmetics, boiling point, pressure, and flow. In my case looks were important so I went with smaller components (radiator, oil cooler, transmission cooler, fan, catch can) to make up for the lack of cooling I increased pressure in order to raise the boiling point, remember boiling water is your enemy. I raised the boiling point by using high-pressure components (radiator, hoses, cap) that easily withstand 24 pounds of pressure. The high-pressure system allows me to run a 90/10 mix that stays cooler than a 50/50 mix. And finally I optimized everything, (air, water and electrical flow) by shrouding the fan and radiator, using all 11/2 inch hose, reducing water-neck restriction and using fan relays. I hope this helps someone save a little time and frustration

   © Copyright 2007. Last update July 2009