Hot Rod History

Ford Flathead Water Pump History - Pumped Up

Plotting The Evolution And Rebirth Of The Flathead Water Pump

By Chris Shelton photographer: Courtesy Of Flathead Jack, Speedway Motors, Tatom Custom Engines, Chris Shelton

"God Bless the Flat Heads!" said the back window on Alex Xydias' pickup. It was the 1952 Bonneville Nationals, and the writing was on more than just SO-CAL Speed Shop's shop truck: the overheads, as the Cadillacs, Oldsmobiles, and Chryslers portended, would soon surpass Henry's valve-in-block pioneer as the default race engine. That very week Ray Brown and Mal Hooper's Hemi-powered belly tank struck the first blow at the Flathead by taking the SO-CAL team's freshly minted C-class record. According to Dean Batchelor, whom I graciously admit inspired this introduction, Bobby Meeks' masterpiece fought valiantly to the end.

Ford produced the last Flathead the following year. For the mathematically disinclined, that was 54 years ago. Of course, you probably wouldn't know it by walking the aisles of a rod run; it seems every third proper hot rod sports one of Henry's valve-in-block engines. In fact, due to technological advances and a healthier-than-ever aftermarket, it's possible to make more horsepower than ever with one of Dearborn's boilers.

Which brings up an interesting point: 75 years since its inception, the Flathead still has that "overheating" cloud hanging over its plank-like heads. It isn't a deserved reputation, either, as it isn't entirely from poor engine design. According to Jack Schafer-or, more familiarly, Flathead Jack-among other things, incorrect ignition timing is one of the leading culprits; a good part of the blame, however, falls squarely on the two knobs bolted to the front of the block: the water pumps.

While the Flathead's pumps evolved in Ford's care during the 21 years the company made them, the aftermarket took the design and ran. Gone are the vulnerable bushings and even the iffy carbon seals. While impellers of yore merely swirled water around the front of the block, modern versions, trimmed and morphed into curved blades by computer development, move water at rates comparable to contemporary standards. Most recently, one manufacturer released early and late pump body and pulley combinations once considered improbable to impossible as recently as only a year ago. Another manufacturer forgoes the pump-in-block design altogether in favor of a conventional overhead-engine pump design. It took us half a century, but we're finally getting a handle on the hot rod world's most illustrious engine.

Which brings up another point: Now that we sort of know what we're doing with the Flathead, the pool of useable blocks is plum near gone. Not to fear, however; they're coming, too.

Bless the Flathead, indeed!

Who's on First...As with any type of gambling, it sure helps to know the players when building an engine. Considering the myriad water pumps Ford produced over the years, a brief review is in order.

First off, for reasons of obsolescence, lack of support, and general unpopularity among the hot rod crowd, we're going to leave the '32-36 pump-in-head engines out of the discussion. Instead, we'll study the more familiar '37-53 design. During those years, Ford offered about eight pump designs that varied by body design, mounting, and pulley arrangement, as noted in the chart on the following page. Also, Ford equipped these pump's shafts with either bushings or bearings depending on the year and application.

This shaft arrangement bears more than passing mention. While early heavy truck pumps and all later pumps feature conventional sealed cartridge bearings, all pre-'49 passenger car and most pre-'48 pickup pump shafts spin within a bronze bushing. While the bearing-equipped pumps endure what we consider normal belt tension by conventional standards, their bushed counterparts won't. While they're just fine for general use and even some hop-up work, they simply cannot bear the belt tension required to operate an alternator or air conditioning pump without failing.

There's also another element common to all stock Flathead pumps: carbon seals. A spring assembly on the impeller side of the pump forces a carbon ring against a fixed plate. While the design effectively prevents coolant from forcing its way out of the water jacket, these seals cannot bear more than 4- or 7-psi coolant pressure, depending on the year. Coolant simply weeps past and eventually destroys the seals at pressures greater than those.

We feel it's important to disclose this original construction on the outset, as each one of the replacement pumps in this story employs a modified or outright different seal design to help them withstand greater working pressures. We'll expand upon this further in the story, but it helps to know immediately.

For a brief primer, consider the following: Passenger designates all Ford and Mercury passenger cars; Ford and Mercury designate designs specific to each marque; while Truck refers specifically to heavy trucks and Pickup, specifically to light trucks. Both can be either marque, as Ford of Canada badged many trucks Mercury and equipped them with namesake engines.

As mentioned earlier, this chart illustrates Ford's original pump configurations. Treat it as reference rather than gospel, as many exceptions to the rule exist due to midyear changes, stock on hand, and manufacturing facility.

78 37-48 passenger low flat pad bushing wide 6 straight
  37-47 truck/PU        
79 37-41 truck low flat pad bearing 2 wide 6 straight
8RT 47-52 truck/PU low flat pad bearing wide 8 curved
8BA 49-53 Ford car angled pad bearing wide 8 curved
  50-53 Ford car     narrow  
  53 truck/PU     narrow  
  52-'53 Merc car     narrow
8CM 49 Merc car raised flat pad bearing wide 8 curved
0CM 50-51 Merc car raised flat pad bearing narrow 8 curved

Flathead JackEnter "Flathead" Jack Schafer. As a Flathead devotee, Jack is, by default, a bit of a curmudgeon. And as curmudgeons go, we begrudgingly admit he's frequently right. This is one of those cases. After working around the Flathead pumps' shortcomings, not the least of which includes the weak carbon seals and combination pitfalls, Jack did something seemingly impossible: He redesigned them. To top that, he had 'em cast in aluminum.

According to Jack, these pumps' computer-designed impellers move water more efficiently. Their radial-bearing-exclusive construction will take more belt tension than even the ball-bearing-equipped stock pumps. They also feature a completely redesigned and enclosed seal that reportedly bears contemporary coolant pressure levels without weeping or failing as the originals certainly will under similar circumstances.

Jack offers these pumps in two basic body designs, each with two subsets. The first design fits '37-48 engines, and as such lacks the bypass configuration. The second design fits '49-and-later engines, and as such features the appropriate bypass. It's the two subsets that really make these pumps shine, though; both body styles are available with single-sheave aluminum pulleys in a choice of the early or late pulley offset.

Above and beyond having really beautiful pumps, it means early-engine adherents don't have to endure irrelevant and awkward-looking bypass ports on their engines. What's even more important than that, however, is the fact that late-engine devotees don't have to forsake the bypass design or the improved impellers to use crab-type ignition systems.

Speedway MotorsRecently, "Speedy" Bill Smith incorporated improved bearings and seals in several popular pump styles. He has them cast from a high-nickel iron and spot-faces the fastener-mating surfaces to ensure proper contact.

While Speedway retained many of the stock design elements, including the six-blade-straight impeller for the early pump and the belt configurations, all boast tighter internal tolerances, combination roller/ball shaft bearings in lieu of all-ball bearings or bushings, and improved ceramic seals, the latter reportedly similar to those used in Nextel Cup race car pumps.

Even though Speedway doesn't offer a modified version of the '49-52 Mercury pump with the raised mounting pad, it does offer modified versions based on the '49-and-later Ford and '53 Mercury truck pumps in either wide or narrow pulley configurations.

Cornhusker Pumps While Flathead Jack and Speedway retained the design attendant to all Ford Flathead engines, Gary Mussman at Cornhusker Rod & Custom bypassed the design altogether. Make no mistake; this kit visually transforms the feel of the venerable Flathead.

Cornhusker's conversion doesn't use two pumps; it uses one, la overhead-engine design. Ironically, it isn't even a Ford unit; it's the pump Chevrolet used on its own '58-65 348 and 409 engines. In fact, it even uses small-block Chevrolet pulleys.

These bolt-on kits include a brand-new pump on an outright basis, adapters, hardware, gaskets, and instructions. While the kit is an entirely bolt-on affair, the optional bushing kit to mount the engine higher in the chassis requires welding brackets to boxed framerails. While Cornhusker offers kits to fit various stock Ford and hot rod applications, its versatility is limited only to a builder's imagination and fabrication skills.

Since this pump features conventional late-model seals and bearings, it'll withstand conventional belt tension and coolant pressures; however, the adapters don't accommodate the late-engine coolant bypass function.