Never run without a thermostat. Thermostats control minimum temperatures and create block pressure. This helps coolant stay in contact with the cooling system and prevents nucleate boiling. Most think if coolant flows too quickly through the system, it will not cool properly. The cooling system is a closed loop system, so if you slow down the flow in the radiator it will stay in the engine longer and will heat up. This is what causes hot spots in the engine which causes detonation. Coolant has to flow fast enough to create turbulence in the radiator. This is what dissipates the heat from the water. Then it's up to the fan and shroud to do its job. This is where it gets sticky. You have to size the fan for the job and always use a full fan shroud. It can't be stressed enough (you have to have a full fan shroud.) Never, ever hang the fan on the radiator core!!
The picture on the right is the fan shroud that I have in my 72' Ford pick-up. The picture on the left is the way a fan shroud should be made. This shroud could also be built for a mechanical fan. (Read the section on "Clutch Drives and Fans). In building a shroud, the center of the fan should be about 1 inch from the radiator. The shroud should be about 2" deep and fit the radiator core tightly around the outside. Use a two core radiator with two 1" tubes and 16 fins per inch. The shroud fitting the radiator tight, gives the fan the ability to create maximum draw on the core. How can you tell if your fan is working? As it draws the air through the radiator, it will decompress and it will feel cooler than the ambient temperature, about 2" ahead of the front of the radiator. If not, your fan is not pulling enough air.
The picture in the middle is a steel fan blade and clutch assembly from a 69' mustang, 428 CJ. The fan and clutch drive should match each other. The bolt pattern on the clutch drive fits many applications. The shroud on the left has an electric fan, but with slight fabrication, it can be made for a mechanical clutch fan combo.
Use a 50/50 mixture of new antifreeze and distilled water or its equivalent. High mineral content, acid or alkaline water reduces pump life. Increase the amount of antifreeze only if needed for your winters. A 50/50 ratio using lowsilicate antifreeze is best for optimum cooling and prolonged pump life. We recommend "Prestone" 50/50 in the yellow container.
We also do matching numbered pumps!