The Ford Barn

Bruce Lancaster · 01-13-2011, 12:12 PM

"there is a plug in the hole you speak..."
I know the plug well. Look again...the vertical stack is the feed from the pump.
At the rear main, oils has two holes seen right and left in the pic. Oil going RIGHT enters the rear main, oil going LEFT enters the filter. From this point, oil has to go through the filter (the plug's purpose) except for the oil that turned right into the RB, then it reenters the feed stack ABOVE the plug and proceeds upwards to the other passages feeding all other bearings and the valve train.
That lower passage is the filter entrance.
The oil returns from the filter right above the plug, and heads on up to oil everything else.
In an engine without the plug (a common mishap amongst inexperienced people assembly a freshly cleaned block), the filter can fill up but has no flow, so the whole engine would be getting unfiltered oil.
One of Smokey Yunick's books has a long essay on ways to rearrange things to get the rear main oil filtered, but concludes that there is no benefit to justify the trouble.

01-13-2011, 12:12 PM	#11
Bruce Lancaster Member Emeritus Join Date: May 2010 Location: Madison, NJ Posts: 5,230	Re: Flathead filter "there is a plug in the hole you speak..." I know the plug well. Look again...the vertical stack is the feed from the pump. At the rear main, oils has two holes seen right and left in the pic. Oil going RIGHT enters the rear main, oil going LEFT enters the filter. From this point, oil has to go through the filter (the plug's purpose) except for the oil that turned right into the RB, then it reenters the feed stack ABOVE the plug and proceeds upwards to the other passages feeding all other bearings and the valve train. That lower passage is the filter entrance. The oil returns from the filter right above the plug, and heads on up to oil everything else. In an engine without the plug (a common mishap amongst inexperienced people assembly a freshly cleaned block), the filter can fill up but has no flow, so the whole engine would be getting unfiltered oil. One of Smokey Yunick's books has a long essay on ways to rearrange things to get the rear main oil filtered, but concludes that there is no benefit to justify the trouble.