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Making mechanical salad: Building a Model T engine the old fashioned way

Published in blog.hemmings.com

Before World War II, modifying cars was as much about what you could adapt as what you could buy. Photo of an auto dump near Easton, Pennsylvania, in 1935 by Walker Evans of the Farm Security Administration, via the Library of Congress.

We’re spoiled for choice, these days, when it comes to improving our vintage engines. You can call up any one of dozens of businesses and order things like aluminum pistons, better-flowing cylinder heads, stroker crankshafts, high-performance cams, and bigger valves. There’s no need to set foot in a junkyard if you don’t want to—and that’s probably a good thing, as high scrap metal prices and encroaching sprawl have annihilated most of the dense repositories of vintage parts that once existed.

Before World War II, with its own set of scrap drives, the situation was reversed. Junk cars going back to the dawn of the automobile were common fixtures in junkyards, dumps, and back lots. During the Great Depression, whole shantytowns, known as Hoovervilles, were sometimes constructed of abandoned cars.

After the 1920s, there also was virtually no automotive aftermarket aimed at the speed-enthused hobbyist save for what little crossed over from pursuits of the wealthy, like boating. Whether for inboard engines or race cars, the parts that were available tended to be expensive and thus out of the reach of the average Joe.

The net effect of that was that to build a speed machine, one had to become adept at adaptation. Creative backyard engineers knew what the innards of their engines looked like and they spent a lot of time dissecting dead cars to see what might be made to fit their car and improve its performance.

Recently, I had occasion to contemplate these clever mixtures of parts. My original plan for the engine in my 1923 Ford project was a 1926 engine improved with the addition of a 1928 Chevrolet crankshaft and rods. That’s a fairly common improvement in Model T’s as the Chevrolet crank is the rare Chevy part actually stronger than its equivalent from Ford.

A pre-1929 Chevrolet four-cylinder crankshaft is an upgrade for the Ford Model T’s “bent paperclip.” Photo courtesy Clayton Paddison.

The reasons for that rarity was Ford’s emphasis on high-quality metal and GM’s desire for low production costs. Even those racers, like John Gerber, who used Chevrolets as the basis for their cars knew that things like Chevy axle shafts weren’t to be trusted and usually adapted Ford pieces instead.

While a Model T crank from the late EE series is a decently stout piece, the Chevrolet crankshaft is still better engineered. Model T restorers snap up EE cranks whenever they become available, leaving the Chevy crank slightly more plentiful thanks to the low survival numbers of the wood-framed Chevy bodies and their dainty rear axles. Chevrolet engines, along with many other non-Ford units, remain somewhat plentiful thanks to second lives as stationary powerplants running generators, sawmills and the like.

The only problem with my plan to use a Chevrolet crank in my Model T is that I just learned that my ’28 Chevrolet donor engine was scrapped without my knowledge. Not only does it pain me to see irreplaceable vintage parts sent for recycling, but it leaves me in the lurch. I haven’t picked up my 1926 engine yet, but the odds are against it having an EE unless one was swapped in during a past rebuild.

A friend offered me a Chevy four crankshaft he had in his parts pile, but the problem is that it lacks connecting rods. Of course, I could hunt down a set of original Chevrolet rods, but I knew that Gerber actually had problems with his rods, which led to him getting into the connecting rod business. Custom rods are an option, of course, albeit an expensive one, but I couldn’t help but wonder what other kinds of OE rods might be adapted.

The original plan, now almost wholly abandoned, centered on a 1928 Chevrolet engine and a 1926 Ford body. Art by Clayton Paddison.

The reason I had a 1928 Chevrolet engine to begin with, (aside from the fact that it was only $75—how do you walk away from that?) was because my original plan, circa 2010, was to use the entire engine in a 1926 Ford touring car. As a consequence, I had spent a lot of time reading one of the best HAMB threads—1928 Chevy 4cyl Motor–which goes into excellent detail on exactly how Chevy fours were tuned to take on Ford Model A engines at the dry lakes and how to turn one into a worthwhile powerplant for a hot rod. Previous experience with that thread, meant I knew where to look when it came to a question of connecting rods for my Chevy crank.

The usual suspects were there—Curtiss OX-5, Durant, and 1936 Pontiac Six. Of course, each of those carries with it certain challenges. The OX-5 was the engine used in the World War One JN-4 “Jenny” biplane, so there aren’t large numbers of them just lying around to pick apart any more. The Durant rods aren’t very closely identified—were they from a Durant 4? A Star? Nobody seemed to know. The ’36 Pontiac rods seemed promising, but not only does my Hollander Interchange Manual tell me they’re a one-year-only part, but it seems they’re better suited to the roomier block of a Ford Model A or B engine and not the tight confines of a Chevy four or Model T.

After discounting these somewhat exotic choices, I was left with one that is perfectly in keeping with my original KISS philosophy—Ford Model A rods. One of the beauties of building a Model T is that even Model A pieces are heavy duty by comparison. They’re also available brand new, complete with insert bearings.

One interesting issue that arises from all this is that of pistons. Stock Model T connecting rods are seven inches long, those from a ’28 Chevy are 7 3/8-in. and Model A rods are 7 ½-in. When installing a Model A crank and rods in a Model T block (a more complicated process than the Chevy crank, but one that gains another quarter inch of stroke) often the rods are shortened or custom pistons are made. In the 1928 Chevy block, the additional rod length moves the piston up in the bore and increases compression—something very desirable in that engine, as the stock ratio is only 4.75:1.

The well-sealed 1936 Pontiac Six was famous among early speed enthusiasts for its adaptable connecting rods. Image courtesy Old Car Brochures.

At the end of the day, all this may be academic. If my Model T engine has a functional crank, and I presume it does based on my discussions with the seller, it will get a set of aluminum pistons, a hotter camshaft, stainless valves, and adjustable lifters, but otherwise be left alone internally. My inner gow jobber bristles at this but having owned cars with engines that outpaced their chassis, I know where I prefer to spend my money first. It’s enough for now.

Someday, however, I will have the mechanical salad that so characterizes the coolest gow jobs. After all, recreating that kind of history is an enormous part of why I’ve undertaken this project to begin with.