Electric Fans
The toughest question when choosing an electric is how to pick the right one. There are dozens of electric fans out there and unfortunately no accurate backyard test for fan efficiency, but we've uncovered some handy shortcuts that can help you choose the best fan for your application. As a general rule, straight-blade fans move more air than curved-blade fans, but you'll pay the price in terms of increased noise.
There is no common industry standard for rating electric fans. Most companies use a cfm rating, often expressed in free-flow and not when placed behind a radiator. This makes comparisons of electric fans difficult. Spal publishes its test data on its Web site for each electric fan. Any fan's highest cfm rating occurs with zero static pressure, or with no airflow restriction in front of the fan. Spal expresses this restriction in terms of inches of water. As the restriction increases (with a thicker radiator core, for example), flow volume drops while current flow increases slightly. According to Jason Schmidt at Spal, one rule of thumb is 10 amps of current flow per 1,000 cfm of air. This is not accurate in all cases, but if you find a fan rated at 3,000 cfm that only requires 10 amps, the cfm rating may be optimistic. Spal rates all its fans, and the three we investigated revealed 17 amps for 2,000 cfm, 21 amps for a 2,360-cfm fan, and a third pulling 26 amps at 3,000 cfm, all rated at zero static pressure.
Twin fans can be a plus in tight-clearance situations, since staggering the two fans moves them away from the water-pump pulley. This is a twin Spal-fan setup that incorporates small rubber flaps that open at higher vehicle speeds to improve airflow.
Two fans usually can cover more radiator surface area than one large fan, which makes the twin-fan systems generally more efficient. Twin-fan performance is also often enhanced by built-in shrouds that pull air in from the entire core surface as opposed to just the area of the radiator covered by the fan. To boil it all down, if you're experiencing overheating difficulties and the rest of the cooling system is optimized, increasing airflow with a pair of smaller fans covering the entire radiator core will generally improve airflow and efficiency.
Aluminum Radiators on a Budget
Aluminum radiators are nice, but they can be expensive, costing between $400 and $550. But cruising through the Summit catalog we ran across Summit race radiators. These are universal crossflow aluminum radiators with no mounting tabs and with either GM- or Ford-style inlet and outlet configurations. These radiators are a two-row design with 1-inch tubes, and come with a machined-aluminum filler neck welded into place. For a person who is willing to do some simple mount fabrication, these radiators can be fitted to many different applications. We decided to bolt one into our 455-urged '64 Olds F-85 that was getting by on the stock vertical-flow radiator originally intended to cool a 330ci V-8. Because the F-85 uses rubber saddle mounts on the top and bottom, it turned out to be an incredibly easy installation. The only extra work we had to do was to add an external B&M trans cooler to accommodate the automatic transmission since these universal radiators do not come with internal trans coolers. One limitation to using a completely separate trans cooler is that in heavy traffic, a loose converter may raise the trans temperature due to extra slippage. If that's the case, this may require a small electric fan attached to the trans cooler. Of course, the extra trans cooler and fittings also add to the overall cost of the radiator swap, so do your homework first before just buying the least-expensive radiator.
In our case, there wasn't enough room for an electric fan between the radiator and the water pump, so we had to stick with our engine-driven fan, which is unfortunate since it definitely eats horsepower. We'll also have to fabricate a shroud for this combination to optimize airflow through the radiator.
The particular Summit race radiator we ordered for our '64 Olds fit almost exactly like the original. What made this easy was the top and bottom rubber-mount application. | 
Be Cool and Summit offer these slick, universal aluminum electric-fan brackets that slip over the top and bottom portions of the radiator to create a very rigid electric-fan mount. | 
Our buddy Tim Moore adapted a Summit race radiator to his '67 small-block Chevelle with simple aluminum L-brackets TIG-welded to the radiator. |
Summit also sells these nice, fabricated aluminum shrouds for the more popular core sizes, which can be ordered either alone or with an electric fan. The shrouds are priced well under $100 and look very professional. | | |