Getting the Right Pump for Your 1937–48 Ford Flathead V8
Two Water Pumps, Two Sides: Getting the Right Pump for Your 1937–48 Ford Flathead V8
If you’re new to early Ford Flathead V8s, one look under the hood reveals something a little different from most later engines: there are two water pumps—one on each side of the engine.
And no, they aren’t interchangeable.
For 1937–48 Ford and Mercury passenger cars and 1937–47 Ford pickups equipped with the V8, C&G Ford Parts offers the two pumps you need:
78-8501-B — Right-Hand Water Pump (Passenger Side)
78-8502-B — Left-Hand Water Pump (Driver Side)
Knowing which is which matters, especially when you’re replacing only one side.
Why Does a Flathead Ford Have Two Water Pumps?
The Flathead V8 cooling system reflects the engine’s distinctive architecture. Instead of using one centrally located water pump, Ford used a pump on each bank of the V8 to circulate coolant through the engine and radiator, keeping in mind each side of the engine has a separate cooling jacket.
That makes both pumps important to the cooling system. A worn, leaking or noisy pump on either side deserves attention. On a restoration that has been sitting for years—or an engine with an unknown maintenance history—it’s also worth inspecting both pumps rather than assuming the other side is fine simply because only one is leaking.
Right Hand or Left Hand? Here's the Easy Way to Remember It
Early Ford parts terminology identifies left and right from the driver's position looking forward, not from somebody standing in front of the car looking into the engine compartment.
So:
78-8501-B — RIGHT HAND = Passenger Side
78-8502-B — LEFT HAND = Driver Side
Standing in front of the radiator looking toward the engine can make this seem backwards. When in doubt, think of yourself sitting behind the steering wheel. Driver's side is left. Passenger side is right.
78-8501-B Right-Hand Water Pump
C&G part number 78-8501-B is the right-hand, or passenger-side, V8 water pump.
It fits 1937–48 Ford and Mercury passenger-car applications and 1937–47 Ford pickup applications as listed in our fitment data. This is a bearing-type pump and includes the mounting gasket.
If you're looking under the hood from the driver's seat, this is the pump on your right.
78-8502-B Left-Hand Water Pump
C&G part number 78-8502-B is its counterpart for the left-hand, or driver's side, of the engine.
It covers the corresponding 1937–48 Ford and Mercury passenger-car and 1937–47 Ford pickup V8 applications. Like the right-hand pump, it is designed as the correct side-specific replacement for these early Ford cooling systems.
Remember: 8501 = right/passenger side. 8502 = left/driver side.
That little bit of Ford part-number knowledge can come in mighty handy the next time you're staring at an old Flathead.
Don't Ignore the Other Side
If one water pump has reached the end of its service life, take a close look at the other one while you're there.
Check for coolant leakage, shaft play, bearing noise and signs that the pump has been on the engine for a very long time. Replacing a questionable pump while the cooling system is already drained can be considerably easier than doing the job all over again a few months down the road.
That doesn't mean both pumps automatically need replacement every time one fails. It means an old Ford deserves an inspection rather than a guess. The 78-8501-PR Left and Right-hand water pumps are a better deal economically at $189.90 for both sides as a set. While you are inspecting under the hood and the hoses are removed, make sure you check your thermostats for the old flathead.
The Right Parts for Your Early Ford
These pumps cover a long and popular stretch of Flathead Ford history—from prewar cars and pickups through the immediate postwar years. Getting the correct pump means checking the year, application and which side of the engine you're working on before placing the order.
At C&G Ford Parts, we've been helping people keep old Fords on the road since 1978. If you're unsure which pump fits your Ford, Mercury or pickup, give us a call. You'll talk to people who know these cars and actually drive classics themselves.
Need the passenger-side pump? Choose 78-8501-B Right-Hand Water Pump.
Need the driver's-side pump? Choose 78-8502-B Left-Hand Water Pump.
Need both pumps? Choose the 78-8501-PR Right-Hand and Left-Hand Water Pumps as a set.
And if, your Flathead needs both, well… Henry gave you two pumps for a reason.
Keep it cool. Keep it Ford. And keep it on the road.