Flathead Ford V-8 Engine Oil & Filtration Systems


Joe Abbin

©2012 Roadrunner Engineering

Albuquerque, NM

Flathead Ford Oil Filtration

Every engine benefits from clean oil! A major requirement to provide clean oil is an oil filter. Ford was slow to provide a real oil filter for the flathead V-8 and one did not become available until 1936, when an early design oil filter was offered as a dealer installed accessory. It was recommended for service in dusty areas. The most commonly seen flathead oil filter with a replaceable element (see Figures 1 and 2) first became available as an accessory in 1940 and later as standard equipment in 1946. These units were commonly retrofitted on earlier engines for longer engine life.

The stock filter does not filter all the oil, all the time. A schematic of the stock oiling system for the 8BA (1949-1953) style flathead is shown in Figure 1. Studying this figure, we note that part (most) of the oil pump output goes to the engine without filtering and the remainder goes to the oil filter in a parallel flow arrangement. While 100% of the oil is not filtered in one pass, the stock filter is effective nevertheless, filtering all of the oil in about five minutes at highway speeds. See Roadrunner Engineering test results below.

Various options for converting to “full flow” or other systems, which filter more of the oil, more of the time, are described in other sources. Converting to one of these systems has pros and cons, but in my view is not generally worth the effort.

A point not to be missed is that the flathead Ford, like all engines, should retain an external oil filter system whether stock or aftermarket. The flathead oil pump - pickup screen and the sludge traps within the crankshaft throws are woefully inadequate for oil filtering by modern standards.

How Much Oil Does the Ford Flathead Oil Pump Circulate and How Much Gets Filtered?

The stock flathead oil pump as shown in Figure 3 is a positive displacement gear-type, capable of circulating about 15 quarts per minute under ideal conditions when the engine is spinning at 2000 revolutions per minute. A recent test at Roadrunner Engineering demonstrated that a stock 1946 to 1953 oil filter with a restrictor flows about a quart and a half of oil per minute through a clean filter under meaningful conditions of oil pressure (55 psi), temperature (180F) and viscosity (15W-40). Thus under the preceding conditions, about 10% of the oil pumped by the stock pump will go through the filter and all the oil in a 5 or 6-quart system will be filtered in less than 5 minutes. Not bad and certainly worthwhile for engine life! Actual flow through the filter will differ from our estimate depending on the actual operating conditions.

Additional Notes/Cautions - Stock Oil Filter Systems  

When using the stock flathead oil filter system, it is important to retain an oil restrictor at the inlet to the filter canister. See Figure 4 for the different types of restrictors used. The fittings pictured incorporate a .060” (approximately) diameter restrictor hole to prevent too much flow through the filter, particularly if the filter element is not installed (ouch!). The 1950 and earlier Ford engines with filters used a restrictor like that pictured in the center of Figure 4. The Eaton/Weatherhead catalog still shows a similar replacement part available under catalog number 1215. The 1951-1953 Ford engines and the 1949-1953 Mercury engines incorporated the restrictor into a “T” fitting that also mounted the oil pressure sending unit. The part numbers are 8CM-6073 for the Mercury (on the left in Figure 4) and 1BA-6073 for the Ford (on the right in Figure 4).

Additional Notes/Cautions - Full Flow Oil Filter Conversion Systems  

A stock or “Beehive” type parallel flow oil filter that uses a stock-type filter cartridge will not flow enough oil for a full-flow conversion and will result in almost instant engine destruction. A filter cartridge designed for full flow must be installed for adequate oiling with any type of “full flow” flathead oil filter conversion. No oil flows if the filter inlet/outlet lines are simply plugged with these conversions. A by-pass line must be installed if a filter is not used (not recommended) with these systems. Read the instructions for any conversion system! 


Joe Abbin

Roadrunner Engineering

PO Box 53296

Albuquerque, NM 87153


www.blownflathead.com or www.roadrunnerengineering.com

For additional Flathead Ford building tips see Joe’s latest book, 335 HP Flathead Ford V-8 Performance Handbook available on the websites above or many fine bookstores.

Figure 1 - Factory Schematic of 1949-1951 Mercury Engine Oiling System

Figure 2 - Stock Oil Filter Installation on a 1953 Ford Engine

Figure 3 - Stock 8BA Type Flathead Ford Oil Pump and High Volume Version