Small Block-Ford Cooling System and Front Dress Parts Interchange

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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Radiator

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.

Ford used the standard 201⁄4-inch-wide compact/intermediate radiator on non–air conditioned packages prior to the 1970s. These were originally two-row-core radiators. Any radiator shop can mate your Ford top and bottom tanks to a new core.

Here is a 201⁄4-inch standard small-block radiator for compact and intermediate Fords with a four-row core. When you specify a four-row core, you greatly increase cooling capacity. Add a fan shroud, the right fan, and proper fan depth, and you improve cooling even more.

Before you purchase a reproduction radiator or have your existing radiator re-cored, think about automatic transmission fluid cooling. Make sure you order a radiator for an automatic transmission vehicle, even though most already have the cooler.

Shown here are two 201⁄4-inch-wide radiators. On the left is an original-equipment radiator with the properly stamped top tank. On the right is an aftermarket brass and copper radiator, approximately 19 inches wide, which just doesn’t offer enough cooling capacity. When you order a radiator, be sure you specify the correct dimensions. They are not all the same.

This 19-inch radiator has been installed in a 1965 Mustang with the 289. It has proper fan shrouding and a five-blade fixed fan. However, due primarily to sizing, this Mustang suffers from overheating issues.

This supersize 24-inch radiator is for 1967–1970 compacts and intermediates with air conditioning. Use this radiator with a three- or four-row core to ensure proper cooling capacity. This radiator is secured by rubber mounts at the bottom and a rubber-insulated top mount.

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.

Packaging Considerations

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.

This 24-inch radiator in aluminum from Redline Cooling has Spal fans. Electric cooling fans are very efficient if you specify the right size. Be sure to provide the correct electrical support system (heavy-duty wiring and relays) and use switched power with the ignition on only.

This Redline Cooling aluminum radiator has been installed in a 1968 Mustang. The aftermarket offers many great aluminum and copper/brass radiators that improve cooling capacity. The main thing you want to remember is fan-to-radiator clearance when you order a radiator. You want a minimum of 1 inch.

Ford began to improve cooling issues in 1970 when it went to a vertical tube crossflow radiator (water pump inlet on the opposite side from the outlet). In 1971, Ford kicked it up a notch with true horizontal tube crossflow radiators. This turn of events greatly reduced the number of overheats.

Here’s the Ford crossflow radiator with shroud and flex fan. The flex fan offers better cooling but with a lot of noise. Horizontal-tube crossflow radiators have become the norm throughout Ford car and truck lines in the years since.

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.

Thermostat

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.

In the 1980s, Ford became more concerned with vehicle weight and cooling capacity. This is an original-equipment crossflow aluminum radiator in a 1989 Mustang GT with 5.0L High Output power. There’s still room for improvement here with a good aftermarket aluminum radiator.

The Griffin crossflow aluminum radiator offers additional capacity for the 1979–1995 Mustang with 5.0L High Output. Note the factory fan shroud and plastic clutch fan. Because the factory clutch fan is so light and efficient it does not rob power.

Thermostat selection is based upon model year and how you’re going to use your engine. Fords prior to electronic engine control call for a 180-degree F thermostat. When you have EEC you must have a 190- to 195-degree F thermostat. SEFI comes online at 192 to 195 degrees F. If you are having overheating problems, the problem is not the thermostat temperature rating. And using a 160-degree F thermostat does not solve overheating problems.

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.

Molded and reinforced radiator hoses engineered to fit the application remain the best choice. Avoid flexible aftermarket hoses. The blue Police Package/Special Service hoses are a cut above black original equipment.

Regardless of what some hose manufacturers and technicians may tell you, always use an anti-collapse spring in the lower radiator hose. Hose collapse happens with the engine at high RPM and the water pump out-pumps the hose capacity.

Cooling system filters are designed to capture iron and aluminum particles from a fresh engine and keep them out of the radiator. Use a cooling sys-tem filter with a fresh engine, checking it periodically for contamination.

Most vintage Fords were fitted with tower-style hose clamps, which were quick-install assembly-line clamps. They are one-time-use clamps. Opt for a good aftermarket stainless steel worm gear professional-grade hose clamp. If you put a cooling system to the test, use two clamps at each end.

The 351C block is fitted with this cool-ant flow restrictor, which must never be removed. Later 351M and 400 blocks had a cast-in restrictor as part of the block. If your Cleveland block is missing this restrictor, replacements are available from the aftermarket.

Anti-Collapse Spring

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.

Radiator Cap

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.

Radiator cap pressure depends on your Ford’s model year. The higher the cap pressure, the higher your cool-ant’s boiling point.

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

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.

Early 1962–1965 small-block Fords were fitted with cast-aluminum water pumps with the inlet on the passenger’s side.

Late 1965–up 289 High Performance engines and all 1966 289s had this cast-iron water pump. Aftermarket high-flow cast-iron water pumps look basically the same as original equipment without the Ford casting number.

This is an aftermarket 351C/351M/400 water pump. It illustrates what happened in 1970 on all Ford small-block V-8s: Ford went to a true crossflow cooling system, which meant moving the water pump inlet to the driver’s side of the engine. You must have a compatible timing cover to go with the 1970–up crossflow water pump on all 302/351W small-block Fords.

With the serpentine belt drive came this reverse-rotation aluminum water pump on 5.0L and 5.8L engines. If you have a factory serpentine belt drive, you must have a reverse-rotation water pump and compatible timing cover. Although the clockwise and counterclockwise rotation pumps and timing covers look similar, they are not compatible. The pump and timing cover must match.

On the right is the redesigned timing cover for the 5.0L High Output engine. It first appeared on the MN-12 1989 Thunderbird and Cougar, then the SN-95 1994–1995 Mustang GT. When compared with the more traditional small-block timing cover on the left, you can see the difference.

Ford went to this more petite water pump with the 1989 MN-12 and SN-95 1994 Mustang GT 5.0L engine to reduce the overall length of the engine. This water pump does not fit a conventional small-block Ford timing cover.

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.

Small-block Fords not fitted with air conditioning received this 17- to 18-inch four-blade “X” fan along with the appropriate spacer and pulley. It did not employ a shroud and was positioned approximately 1 inch from the radiator.

The 289 High Performance V-8 was fitted with this 16-inch four-blade fan (C3OZ-8600-C) and a shroud. The fan should be located halfway into the shroud.

This is an aftermarket six-blade 17-inch steel fan designed to improve engine cooling. Properly installed halfway into the fan shroud, it is very effective but noisy. Although it moves a lot of air it is not efficient.

This is Ford’s five-blade 17- to 18-inch flex fan, which was used from 1967 through the mid-1970s. Although this particular application doesn’t employ a fan shroud it should. When properly equipped, the fan should fit halfway into the shroud. Flex fans have a history of failure, which means you may want to think twice about using one. If you’re performing a restoration, err on the side of correctness and authenticity.

The most efficient engine-driven fan is the thermostatic clutch fan. This seven-blade clutch fan is very effective, engaging only when it is needed based on radiator temperature. The thermostatic fan and clutch are independent assemblies. Fans and fan clutches are available from sources such as Flex-A-Lite as well as a number of classic car parts sources.

Fan spacers are available in several widths. Selection boils down to proper fan depth into the shroud or proximity to the radiator. Choose a Ford fan spacer for best results due to water pump hub and pulley fitment. The two spacers on top here are Ford spacers.

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.

Front Dress

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.

Small-block Ford front dress pack-ages are simple in scope. Unless equipped with air conditioning and power steering you have one bracket only, which supports the alternator. Air conditioning and power steering brackets are separate components. If your small-block has the Thermactor air pump, the front-dress package becomes more complex.

This is the Eaton power steering pump and bracket common prior to the 1965 model year, although some early 1965 model-year Fords had this pump. Some have a remote reservoir mounted at the inner fender.

Power steering fluid coolers arrived in the early 1970s on Fords fitted with the Saginaw steering gear. Not all Fords with the Saginaw steering gear were fitted with this cooler. It is located on the return side of the system, never on the pressure side. It is also more common on air-conditioned vehicles.

Here is a 1968 289 with the cast-iron Tecumseh compressor and simple belt tension adjustment located on top. This adjustment system was common through the late 1970s.

Beginning in 1965, Ford dropped the Eaton pump and used the Ford/Thompson power steering pump. Prior to 1967, the Thompson pump had a large filler neck. Beginning in 1967, the Thompson pump had a skinny filler neck and dipstick tube (shown). The Thompson pump was common on most Fords until early 1978 when it was dropped in favor of a new, light-weight, aluminum Ford pump.

Small-block Ford V-8s were fitted with two types of air conditioning compressors early on. The York compressor (shown) is cast aluminum and lighter than the cast-iron Tecumseh compressor. They are interchangeable. This is a 1967 289 with the York compressor and belt tension adjustment down at the water pump.

This high-efficiency Nippondenso 6P148A wobble plate air conditioning compressor was common from 1982–1993. It was replaced by the more compact FS10 compressor in 1994.

In mid-1978, Ford transitioned to a new lightweight aluminum power steering pump, which was first used on 1978 Fords. It can be fitted with a single-groove V-belt pulley or a serpentine belt drive pulley.

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

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