Ford Small-Block Engine Interchange Guide: Cooling System

Many don’t think about the cooling system until it’s too late. But the cooling system is one of the first areas that need to be considered because it is an engine’s life insurance policy. Ford engines have always struggled with cooling problems due mostly to factory radiators that weren’t large enough for the task. Smallblocks struggle most because they’re mostly installed in compacts and intermediates, which don’t have enough radiator, or air flow, due to limited grille size. Small-block-equipped Mustangs, Falcons, Fairlanes, and Comets suffer the most due to their tiny radiators. Overheating is the norm, but it doesn’t have to be.

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Radiators

In the years since these cars were rolling off Ford assembly lines, the aftermarket has solved many of the cooling problems by adding rows of cooling tubes to the radiators. Early Mustangs, Falcons, Fairlanes, and Comets were cursed with small radiators. This limited cooling capacity, and they liked to split at their top tank seams, spraying coolant all over the engine compartment. Reproduction radiators available today offer identical-to-original construction coupled with better quality and improved cooling capacity. There is also a wealth of aftermarket aluminum and brass radiators designed for the demands of motorsports and severe-duty applications. Based on what is available today, no Ford small-block should ever overheat.

 

This is the standard 20-inch-wide radiator for Mustang, Fairlane, Comet, and like Ford compacts. In their standard two-row core configuration, these radiators are not enough capacity. You want a three- or four-row core.

 

Here’s the larger 24-inch radiator for air-conditioned Mustang, Cougar, Fairlane, and Cyclone with greater capacity.

 

For 1966–1967 and newer Ford compacts and intermediates, there is the higher-capacity radiator for airconditioned Fords and Mercurys, which offers better design and higher cooling capacity. This radiator is seen most often on air-conditioned Mustangs, Cougars, Fairlanes, Torinos, Comets, and Cyclones.

See complete chart (on page 85) and guide to Ford and Mercury radiators, which enables you to choose the right radiator for the job. The key to properly matching radiator and transmission is to reach for the highest capacity possible, paying close attention to inlet and outlet positions, and the use of automatic transmission cooler connections, if necessary, for your application. Another important issue to keep in mind is radiator height. Mustangs and Cougars through 1970, for example, have a lower hoodline, which means radiators that are 1 inch shorter than those for full- and intermediate-size car lines. If you opt for a 17-inch-tall radiator for a 1965–1970 Mustang/ Cougar, your hood will not close. When reaching for cooling capacity, look at width and thickness, taking care not to choose a radiator that’s too wide for the radiator support. Also keep in mind crossflow versus vertical flow in your search.

 

Water Pumps

Choosing the right water pump for your small-block Ford doesn’t have to be a daunting task. There’s no magic here. A handful of basic types were used. All Ford small-blocks, except the 289 High Performance, prior to 1966, were equipped with aluminum water pumps (C5AZ-8501-K) from the factory. As a result, they were equipped with a timing chain cover specific to the aluminum water pump (C4AZ-6019-B). This timing cover is not compatible with the cast-iron water pumps.

Whenever you’re building a smallblock Ford, experienced builders advise against using the pre-1966 aluminum water pump unless you’re striving for originality. Instead, upgrade to the castiron water pump (D3UZ-8501-A or C5AZ-8501-A). The important thing to remember is the difference between the D3UZ and C5AZ cast-iron pumps. The D3UZ pump is the standard cast-iron water pump used on 289, 302, and 351W engines through 1969. The C5AZ highflow pump was originally 289 High Performance-specific from 1965–1967. These water pumps are interchangeable, with their inlets located on the righthand side of the vehicle.

Because nearly all of these water pumps have found their way into the rebuilding supply line and have lost their original identity, casting numbers don’t have the validity they used to. Fortunately, the aftermarket offers a wealth of high-performance water pumps for Ford small-blocks.

 

Although 1966+ small-block Fords received cast-iron water pumps originally, replacement units tend to be cast aluminum, which, due to improved casting technique, are better and lighter than iron. This is a right-hand inlet water pump, which is 1962–1969 only.

 

Beginning in 1970, Ford went to a left-hand inlet water pump along with a 4-bolt crankshaft pulley and harmonic balancer on smallblock Fords.

 

Like the 302 and 351W in 1970, the 351C also received a left-hand inlet water pump. In fact, the 351C never had a right-hand inlet because it was introduced in 1970.

 

When you’re planning an engine build, plan for improved coolant flow via a high-flow water pump.

 

Here are two examples of small-block Ford water pumps. On the left is a right-hand inlet water pump for the 221/260/289/302 prior to 1970. On the right is the smaller reverserotation water pump for 1994+ 5.0L High Output, which also calls for the appropriate timing cover.

 

 

Ford Racing Performance Parts offers the enthusiast two types of water pumps for small-block Fords: shorty, and regular length for 5.0L engines. The shorty water pump is designed more for street rods and unusual applications where clearance is tight.

 

This is the 171⁄2-inch 5-blade heavyduty fan used mostly with aftermarket air conditioning. What makes this fan a bad idea is inefficiency and noise. It’s heavy and it’s always moving air regardless of engine temperature and speed.

 

Small-block cast-iron water pumps remained much the same through 1969, with a right-hand inlet for the lower radiator hose. Beginning in 1970, 302 and 351W small-block Fords received a new water pump casting (D0AZ-8501-C) with the inlet on the left-hand side of the engine. Boss 302s for 1969 were fitted with a 1969- specific high-flow water pump (C9ZZ- 8501-A). A year later, in 1970, the Boss 302 engine was fitted with the D0ZZ- 8501-B water pump.

The 351C engine, introduced in 1970, was fitted with the D0AZ-8501-E water pump with a left-hand inlet, just like Boss 302, 302, and 351W engines from 1970 and up. The only real difference in these water pumps is flow rate. Otherwise, they are virtually interchangeable.

 

Cooling Fans

Cooling-fan selection is very important because it affects the efficiency of the entire cooling system. This means properly matching engines, applications, fans, radiators, and shrouds. Each component must be up to the task. Unless you’re striving for originality, I suggest using heavy-duty components in all cases. When selecting a water pump pulley, be conscious of size (diameter, sheave width, and number of sheaves). A highrevving 289 Hi-Po or Boss 302, for example, should have a large pulley (6 to 7-plus inches in diameter) to keep pump speed safe.

 

This is the standard 4-blade 173⁄4-inch “X” fan common to non-air conditioned cars with the 19-inch radiator. Most are not equipped with a fan shroud.

 

The humble luxury-car clutch fan is the most efficient cooling fan there is. Use this type, because thermostatic fan clutches only engage when they’re needed. Always use a fan shroud and always make sure fan depth is halfway into the shroud for best results.

 

Here’s the 289 High Performance V-8 4-blade 173⁄4-inch fan with shroud. Fan shrouds do improve cooling because they increase air velocity through the radiator. Key is to get fan depth into the shroud just right. The fan should be halfway into the shroud for optimum results.

 

Goodyear Hi-Miler cooling system hoses are good news for those of you who run vintage or late-model Fords under very demanding conditions. Available in blue, red, or black, the Hi-Miler hoses offer better reliability than most hose product lines out there. Again, always use an anticollapse spring in the lower hose no matter what anyone suggests.

Written by George Reid and Republished with Permission of CarTech Inc