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Why Prewar Car Engines Need Bearings Made From Scratch

The lost art of babbitt bearings. Via Road & Track.

AUG 17, 2017

When he lights the burner, the pot is cold. It is ceramic, roughly the size of a small trash can, and essentially fused to the lump of metal inside it, tin blended with antimony and copper, maybe 100 pounds in total. The whole thing is mounted in a steel cart, next to another virtually identical pot, which is also full of cold metal. There is a lit burner under each.

In about 30 minutes, those burners will melt that metal to liquid, and the pots will become too hot to stand next to comfortably. And then Alec Giaimio, the cart’s owner, will pour that metal onto an engine’s connecting rod.

“I met an old-timer in this business,” he says. “He’d been doing it since 1926. I needed a bearing job on an old Delage. He had a hard time setting up the crank centerline—that Delage had three cams—so I helped him. And he taught me how to pour babbitt, every Saturday for four years. I worked for him in order to learn, had to buy him lunch. That was . . . 1978? 1980?”

Giaimio is a babbitt man. He lives in the San Francisco Bay Area and is widely regarded as one of the best automotive babbitt pourers on earth. And because automotive babbitt is deeply obsolete, he is also one of the last. If you own a prewar road or race car, it almost certainly has babbitt in its engine. If that car gets used hard and doesn’t regularly blow up, Giaimio has probably seen some of its innards.

Babbitt is a loose term for a metal alloy used in bearings. It’s also a process. Consider the crankshaft in a combustion engine: It rotates and is subject to thousands of pounds of force. It has to spin in something. The modern solution is a hydrodynamic shell bearing, a replaceable piece of metal that sits between engine block and crank. Most new engines have many of these, including two at each of the crankshaft’s supporting journals, but they’re also used in or around other rotating bits, like camshafts and connecting rods.

Modern engines feed pressurized oil to these bearings, which helps keep them alive. That’s the “hydrodynamic” part—if the engine is healthy, the bearing doesn’t touch anything. (A layer of oil supports the spinning pieces.) But shell bearings wear out like anything else. When they do, their design makes them easy to replace: You open the engine, typically during a rebuild, pop the bearings out with a fingernail, and replace them.

 It wasn’t always so easy. Until the middle of the last century, most engine bearings were made by custom-pouring liquid metal into place. Many cities had shops that specialized in this—some guy with a ladle, a burner, and a pot full of alloy. He’d heat the metal to melting and then dollop it into place. When the metal had cooled and hardened—about 30 seconds later—he’d set it aside for finishing with machine tools.

The process and the alloy are named after a 19th-century Boston goldsmith. In 1839, Isaac Babbitt patented a type of bearing carrier for railroad-car axles. His patent description notes, almost as an afterthought, that he had also developed an alloy for the load surface on those bearings. The structure of Babbitt’s metal helped make it resistant to galling—wear produced from momentary adhesion during sliding—and on a microscopic level, it had a remarkable capacity for carrying oil. This was an important benefit for early automobiles, many of which lacked oil pumps and relied solely on “splash” lubrication—the calculated hope that a running engine would kick enough oil around its guts to stay alive. (One of my old mechanic mentors used to describe prewar car engineering as “ingenuity crossed with blacksmithing and prayer.” He wasn’t exaggerating.)

The catch lies in the application. Metallurgy is science, but the results of babbitting must be gauged by eye and feel, which means the practice includes a healthy dose of art. Even the tamest engine subjects its bearings to force that would seriously injure a human being. If your poured babbitt isn’t perfect, it will come apart under that load and take the engine with it. And there are myriad ways to make a babbitt bearing imperfect. You can pour it too quickly, too slowly, or at the wrong temperature. Or use the wrong blend of babbitt for the application, allow impurities into the melted metal . . . the list goes on. As with a weld or solder joint, you can kill a good pour through improper prep or sloppy machining. The poured metal has to be free of porosity (internal air bubbles, invisible from outside), it has to adhere properly to the underlying surface, and it has to solidify at the right speed, its structure cooling neither too quickly nor too slowly. And unlike a bad weld, bad babbitt doesn’t always give clues in its finished appearance. You have to watch the work, as it happens.

“After I tin the surface,” Giaimio says, “I can see the capillary action of the babbitt, the oxidation. As it amalgamates . . . if it looks like molasses poured over a piece of glass, or welding to it as it disperses . . . it’ll be like bread dough on a piece of marble, if it’s not sticking.”

Babbitt men are thus on the receiving end of an extraordinary amount of trust. Much of Giaimio’s work goes through a Bay Area restoration shop called Phil Reilly & Company. You build a relationship with your babbitt guy, says Ross Cummings, Reilly’s machinist. “This is a process that really relies on the skill and observation of the guy doing the pouring,” he says. “By the time it gets here, other than the sound”—how the hardened babbitt rings out when its carrier is tapped with a metal object—“we don’t have any way of knowing if it’s good.” And whether, by extension, the engine will grenade when first run hard or have a long, happy life at speed.

And like all skills involving chemistry and feel, the process varies with application. A Model T will run forever with bearing clearances wider than the Atlantic; a backyard mechanic could rebabbitt one of those engines in less than a morning. Experienced hands on a prewar Alfa Romeo straight-eight—a masterpiece whose rebuild can cost more than a new Ferrari—might take 12 hours to do the same job.

The rise of shell bearings made poured babbitt a rarity, but the metal itself is far from dead. Modern multilayer shells usually contain a babbitt layer. The turbines in the Hoover Dam use babbitt bearings, as do the propeller shafts in military submarines. (Ball bearings, Giaimio says with a scoff, “make a racket that can be detected.”) To say nothing of the various oversize industrial machines roaming the planet, using the metal in places no standardized bearing will fit.

“The oldest thing I’ve babbitted,” Giaimio says, “is probably a metal shear made in 1917. Designed to cut metal thicker than your thumb.” The most obscure, he says, was a 75-pound bearing for a rock crusher, poured in place at a quarry. Giaimio’s 1920s connecting-rod clamp came from the San Leandro shop where he learned the trade. His alloy supplier, United American Metals, sold the stuff to both Isotta Fraschini and 1920s Indy 500 legend Harry Miller.

You have to marvel at an ancient craft that both predates the automobile and remains the best answer for some of its problems. Babbitting recalls a time when almost every part on a new car could be reproduced in your local garage, but it is neither simple nor easily understood. It’s just metal and alchemy. And, as with most good mechanical things, a few tools and a bit of faith.

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