Walker
Pressure systems have been around for quite sometime. Older systems started at a 4lb rating; 7lb systems were introduced in the '50s, followed by 15-17lb systems in the '60s, and today's engines run up to as much as 20 lbs. As a general rule of thumb in the street-rodding world, a 15-17lb system works well.
9. How is proper radiator size determined?
Be Cool
One would need to know the required number of Btu/min that needs to be rejected by the radiator. With a given air and coolant speed, select a core that will reject the required amount of heat with a factor of safety. Experience also plays a large role.
Flex-a-lite
Radiator size is determined by the requirements of the available mounting area, the powertrain, and how and where the application will be used. The correct radiator can be determined once these factors are reviewed.
Griffin
There are many factors to consider when sizing a radiator. Not all radiator sizing is based strictly upon the horsepower that the engine is producing, but also the type of fuel the car is running, how much grille area we have to work with, and under what type of driving conditions the car will be used. For most street applications, a good rule of thumb is 1 square inch of core surface per horsepower for a two-row 1-inch tube aluminum radiator.
Mattson's
We try and put the largest radiator in the available area.
U.S. Radiator
There are formulas to determine appropriate radiator size based on engine heat output (operating Btus) and radiator heat transfer rates (also stated in Btus), but my recommendation to a hobbyist is to put in the most efficient radiator that fits up to a four-row copper/brass or two-row aluminum core.
Walker
Unfortunately, being a performance radiator designer and manufacture, we have to use the area given to us (the square inches of the frontal radiator area) by the original automobile manufacture or the custom-car builders. From there, we will need the engine specifications, its modifications, and also its determined air-management package to be used. It is good to remember that the air-management package is just as important as the coolant-management package in their designs and ability to work together.
10. Do you recommend recovery tanks?
Be Cool
Yes, all the coolant that is vented from the radiator by the overflow should be reclaimed by a recovery tank. Recovery tanks allow the cooling system to replenish and helps to ensure that the radiator is always full.
Flex-a-lite
The requirement of a coolant-recovery system is not only environmentally sound, but a good idea to maintain a constant level in the cooling system. Most coolant is not environmentally friendly. It is a pollutant, and therefore should not be released to the ground. Maintaining a constant level in the cooling system will allow it to function better and prevent air from entering the system that could bring with it contaminates that might cause a failure in the cooling system in the future.
Griffin
Absolutely.
Mattson's
We recommend a recovery system on everything we do today.
U.S. Radiator
Rule of thumb is to buy the largest one that will fit in the engine compartment and still look cool. Check the recovery tank often and you'll know the size is inadequate if you find it empty.
Walker
It's a must in the performance field, and it's an advantage but not a cure-all in the street rod world. If you have the correct cooling system design, don't waste your money (I have never needed one).