Of all the engines that have powered hot rods over the years the Flathead Ford is in a class by itself. Certainly not because it’s the most powerful, or the most reliable, they can’t even be described as cheap to build. I can hear Brennan saying, “Yeah, double the horsepower and normally aspirated and you’ve got 200 ponies if you’re lucky, why bother?” As much as I hate to agree with Brennan on any subject, he makes a valid point. The most basic crate engine currently available will make more horsepower, last longer, and cost less overall than a Flathead V-8. So why are so many hot rodders, young and old, intrigued by an engine that went out of production nearly 60 years ago? Certainly in this age of advanced automotive technology there’s no logical basis for building a Flathead—but when did hot rodding and logic have much in common? The fact is the Flathead Ford is a link to the past, a connection to our hot rodding roots—in a word they are traditional.

Although many of the same time-honored techniques that have always been used to hop-up Flatheads are still valid today, there are those who continue to look for new ways to make these old engines better. One of the common contemporary modifications is adding an oil filter.

Stock Oiling System

The Flathead V-8 oiling system was basically the same from 1932-53. Oil is delivered by a gear-style pump driven off the cam (which runs at half crankshaft speed). During its production run the design of the Flathead’s oil pump was changed several times. The early long-body pumps were rated at 30 psi at 30 mph (there was also a second revised long-body pump), then in 1948 the short-body pump was introduced, which, like all its predecessors, had straight-cut gears and produced around 60 psi.

From late 1949-53 a short-body pump with helical gears was used. Another change made in 1949 was the relocation of the pressure relief valve. From 1932-48 the pressure relief valve was in the valley at the front of the block while the ’49-53 pumps have the pressure relief built into the pump. Today the most commonly used pumps are the late-style standard pump and the high-volume version available from Melling and others.

After the oil leaves the Flathead’s pump it’s delivered to a cavity with two passages, one leads to the rear main bearing, which also supplies the lubrication through the crankshaft to the rearmost rod bearings (numbers 4 and 8), and the other passage leads to an outlet on the back of the block for the oil pressure sender as well as the distribution tube that runs the length of the block and supplies the cam bearings, the front and center main bearings, which again supply the rod bearings through passages in the crankshaft.

While Flatheads did not have a factory oil filter until one became optional equipment in 1940, they did have another unique method of trapping some contaminants—sludge traps in the crankshaft. As the ’shaft spun centrifugal force tossed all kinds of “stuff” into the hollow crank pins where it collected (unfortunately all that “stuff” had already been pumped through the engine). The crankpins have holes in each end that are sealed with soft plugs and it is an absolutely critical step in rebuilding any Flathead that these plugs are removed and the passages and sludge traps are thoroughly cleaned.

All things considered, Flathead Fords had a pretty good oiling system. With a late-style pump, proper clearances, and the correct oil, adequate lubrication is not an issue for street-driven engines, however a filter of some sort should be included. Here are three methods of doing that: