Flathead Water Pumps - Pumped Up

"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.