Small-block Ford cooling systems vary depending upon vehicle application. One thing is certain about small-block cooling systems: They were under-capacity right off the assembly line. When you add corrosion and foreign contaminants they only became worse with time. When you consider that Ford had radiators in only two-row core 19-, 20-, 24-, and 26-inch lengths, they were never enough.
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Because the radiator’s job is to transfer engine heat to the atmosphere, you need one that gets rid of excess engine heat, yet not too much. Engines have a temperature range they like to operate in. Vintage engines prefer 180 to 210 degrees F. Late-model 5.0L and 5.8L SEFI engines like it hotter, around 192 to 210 degrees F for cleaner emissions. This means you need a radiator engineered to carry heat to the atmosphere while the rest of the cooling system can safely withstand that heat.
The aftermarket industry offers many radiators for the small-block Ford. You may opt for a brass/cop-per radiator with a three- or four-row core that has adequate cooling capacity. Some terrific aluminum radiator packages, virtually identical to original equipment, offer improved cooling capacity. The difference between aluminum and copper/brass is the number of tubes and tube size. Aluminum radiators have fewer yet larger tubes because aluminum con-ducts heat differently than copper/brass.
There’s endless debate about which is better, aluminum or cop-per/brass. In the end it boils down to what you want your engine to do. Aluminum is preferred in motor-sports competition. Copper/brass tends to be preferred for the street. Each type has pros and cons.
Copper is a better conductor of heat than aluminum, but it weighs more. Aluminum is a good heat con-ductor, but not as good as copper, yet it weighs considerably less. Even though copper is a great conductor of heat, soldered joints tend to slow down the heat transfer process. One great advantage of aluminum is that it is all aluminum and doesn’t have the disadvantages of dissimilar metals (copper and brass), which causes corrosion.
Cooling problems aren’t always related to the radiator. You can have great cooling capacity, yet run into trouble because you haven’t properly packaged your Ford’s cooling sys-tem, or you may have installed cylinder head gaskets backward, cutting off coolant flow to the rear of the engine. These are important issues to consider when packaging an engine build.
You must have the right combination of parts, radiator, fan, water pump, and thermostat. You must also have an engine/cooling system properly thought out and executed so that heat generation doesn’t over-whelm the cooling system.
It is a popular misconception that you can solve overheating problems by removing the thermostat. However, this has never been a good idea because the thermostat is your cooling system’s traffic cop. It allows coolant time to absorb engine heat, then releases hot coolant into the radiator where it has time to trans-fer heat to the atmosphere. Coolant, which has had time to cool down, transfers through the lower radiator hose into the engine, where it has time to absorb engine heat and the process begins all over again.
When you remove the thermo-stat, coolant never has time to absorb or release heat. Cooling is effective on the open highway without a thermostat. However, in traffic, coolant becomes hotter and hotter, and over-heating abounds.
Radiator Hose and Clamps
The best radiator hoses are molded specifically for your small block Ford. You want a high- quality, reinforced, molded hose that will stand up to a lot of heat and pressure for a long time.
Also think about the type of clamp you want to use. Tower-style one-time-use clamps are fine for a restoration but unacceptable for a vehicle that you’re going to drive. Invest in the best worm-gear clamp you can buy. Ideally, it is an industrial stainless steel clamp that’s aviation worthy. Wire-style radiator hose clamps are also a good choice because they have an original equipment demeanor along with durability.
Your small-block’s lower radiator hose should be fitted with an anti-collapse spring, which prevents hose collapse at high engine speeds. Anti-collapse springs are available from most classic car parts deal-ers such as National Parts Depot or Marti Auto Works. One aftermarket replacement hose manufacturer incorrectly states that you don’t need an anti-collapse spring because these springs were used for assembly-line quick fills, which has never been true.
A quick fill does not cause the lower radiator hose to collapse. High engine speeds cause collapse because the engine takes on radiator coolant faster than the radiator can provide it when the thermostat opens. If your small-block overheats on the open road yet cools down when you get back into town, lower hose collapse is probably the cause of overheating.
Another important element is the radiator cap: original equipment examples and aftermarket pressure-release types. Selection depends upon the nature of your project: concours restoration or driver. Reproduction OEM-style radiator caps are available from most classic car parts shops. Release-style caps are available nearly anywhere.
Your greatest concern is cap pres-sure. You want the highest pressure possible, which raises the boiling point of the coolant. Go with the pressure rating recommended by Ford for your model-year vehicle. Older Fords and Mercs generally have lower cooling system operating pressures, around 4 to 10 psi. Newer Fords operate in the 13- to 17-psi range.
No matter how old your Ford is, you should have some kind of cool-ant recovery system to catch excess coolant vented by the cooling sys-tem. You want the coolant to be drawn back into the cooling system as your engine cools. If a coolant recovery system isn’t possible, cool-ant level in the radiator should be at least 1 inch below the cap to allow for expansion without losing any coolant.
You have the choice between two basic types of radiator caps. Non-recovery caps have a single seal, which allows coolant to escape, yet allows air back into the system.
Recovery caps have a double seal so coolant from a coolant recovery reservoir can return to the radiator.
Safety-lever caps allow you to vent the cooling system without getting scalded. The best advice is to allow a hot engine to cool down before opening the radiator cap.
Water pump selection boils down to choosing the correct pump for the job. Unless you’re perform-ing a concours restoration where the Ford casting number and date coding must be appropriate for the application, the field is wide open. If Ford casting numbers and date codes are crucial it becomes very involved because you have to be able to hand-pick the rebuildable casting. Then, you have to find a source willing to rebuild that pump and hand you the same casting back.
Water pumps are simple affairs. You have a hub, shaft, and impeller supported by a shaft and protected by a seal. The impeller is pressed onto the shaft once the entire pack-age is fitted within the cast-iron or -aluminum housing.
Aftermarket water pumps are both cast iron and cast aluminum in both new and remanufactured. Plenty of existing cores are rebuilt every day and distributed into the aftermarket. Thousands of cores are destroyed and recycled too. This makes it very challenging for the restorer because more and more cores are melted down in recycling each day, gone forever.
New replacement aluminum and iron water pumps are available from sources such as AutoZone, NAPA, Advanced Auto Parts, Edelbrock, and Weiand. They elude detection especially if you paint them engine color. They look a lot like original equipment to the point that the only issue is the missing Ford casting number. The trick is to purchase a water pump that fits your small-block’s timing cover and jibes with the radiator.
All small-block Fords prior to the 1970 model year have water pumps with the inlet on the passenger side. From 1970–up, the inlet is on the driver’s side. To improve cooling efficiency, Ford changed to a crossflow radiator in 1970 with vertical tubes. In the following years, Ford went to a true crossflow radiator with horizontal tubes to improve cooling efficiency even more.
As the 1980s unfolded, Ford went from a cast-iron water pump back to cast aluminum for weight reduction. The 5.0L and 5.8L engines had the same basic water pump with driver-side inlet until 1989 when Ford redesigned the small-block’s cooling system to reduce overall engine length for the MN-12 Thunderbird and Cougar and later the SN-95 Mustang. To achieve the room it needed for lower hood lines and a revised upper intake manifold, Ford fitted the 5.0L engine with a smaller timing cover and water pump.
The 351C/351M/400 engines were fitted with Cleveland-specific water pumps with the driver-side pump inlet. Because the 335-series engine family is different than the small-block Ford with a metal-plate timing cover, these pumps are not interchangeable with the 221/260/289/302/351W pumps.
Fans and Spacers
Proper cooling fan and spacer selection depends upon vehicle type and how the vehicle is equipped. Quite a number of different fan types were used on small-block Fords from 1962 to 2001. Some late-model applications had electric cooling fans. Non–air-conditioned vehicles typically had X-type four-blade fans of various diameters devoid of a shroud. Thermostatic clutch fans in the 17- to 18-inch range with shrouds are primarily for air conditioned vehicles.
Flex-blade fans arrived in 1967 and were used in production until well into the mid-1970s. And finally, fixed 5- or 6-blade fans with shrouds were for heavy-duty cooling systems.
The most efficient engine-driven cooling fan is the thermostatic clutch fan, which engages as needed depending on radiator temperature. The thing that makes the thermo-static clutch fan effective is its speed, which tends to be conservative com-pared to engine speed. You want undisrupted airflow across the radiator, meaning just the right air speed so there’s no turbulence. Turbulence across the fins and tubes hinders heat transfer. This is why you want smooth, undisrupted airflow.
At highway speeds, the thermo-static clutch fan tends to freewheel to the point that the vehicle slipstream roars through the radiator without help from the clutch fan. At lower speeds, the clutch fan slowly engages, moving more air through the radiator. In 1967 Ford introduced the flex-blade fan in some air-conditioned applications. At idle speed, the blades are angled to move large quantities of air through the radiator. As engine RPM increases, the blade angle flattens out, reducing drag. Because the vehicle is moving, the slipstream coming through the radiator gives heat a place to go. At the same time, fan speed has increased and the blade angle has changed so the fan is moving less air.
The downside to the Ford flex fan is noise. There is also some level of failure risk because these fans have been known to throw blades, which makes them dangerous. Unless you are performing a concours restoration, the flex fan is discouraged.
If you are using a shrouded fan, fan placement should be halfway into the shroud for best results. Flex fans should never be used unshrouded. If you’re running an unshrouded “X” fan, you want the fan 1 inch from the radiator core. Ford produced a variety of fan spacers. Use a Ford fan spacer even if you’re running an aftermarket fan. Although there are plenty of aftermarket fan spacers, the best choice is a Ford spacer.
All small-block Fords employed a very simple front dress package through the 1960s and 1970s. This accessory package consisted of a generator or alternator bracket, pivot bolt, spacer, and adjustment slider. When Ford began installing the Thermactor smog-pump system in 1966, front dress became more complicated on California-delivered vehicles.
Air-conditioned vehicles were fit-ted with a compressor platform and adjustment system consisting of an idler pulley. Because the air conditioning belt tended to chatter, Ford issued a technical service bulletin in 1967 that called for the installation of an additional idler pulley between the compressor and crank pulley to quiet operation.
Early on, power steering pump brackets and adjustments were of stamped steel construction with the pump hanging way out on the driver’s side. From 1962 to 1964 small-block Fords were fitted with an Eaton power steering pump with a stamped steel reservoir. Some applications had a remote reservoir mounted on the inner fender.
Beginning in the 1965 model year, Ford used the Ford/Thompson power steering pump with a filler neck and dipstick. For 1967, Ford redesigned the pump housing and changed to a narrow filler neck and dipstick tube, which remained through the 1978 model year.
In mid-1978, Ford went to a lighter aluminum power steering pump with a plastic housing and filler neck. This pump entered service with a V-belt pulley in 1978. When Ford changed to a single serpentine belt drive on the small-block Ford for 1979, the new Ford aluminum pump was fitted with a serpentine belt drive pulley. The beauty of this new pump was its easy-to-adjust design. This pump was installed on small-block Fords through the end of production in 2001.
The small-block Ford has been fitted with several types of air conditioning compressors. During the 1960s and 1970s, York and Tecumseh piston compressors were common even with aftermarket systems. York compressors were cast aluminum while the Tecumseh compressors were iron heavyweights. If you have a choice the York is suggested due primarily to its weight savings. Some small-block applications in the 1970s had Frigidaire compressors.
In 1982, small-block Fords were fitted with a new high-efficiency Nippondenso wobble-plate air conditioning compressor (6P148A), which consumes less energy than the older York and Tecumseh compressors. It also weighs considerably less. It was dropped for the more compact unit (FS10) in 1994.
Belt tension comes from a spring-loaded belt tensioner, which is an integral part of the serpentine belt drive system launched in 1979. The serpentine belt drive system changed in 1994, with the air conditioning compressor relocated under the power steering pump.
Written by George Reid and Posted with Permission of CarTechBooks