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<h1>Bypass Oil Filters on StepDown Hudsons</h1>
<p class="description">
These are my thoughts on oil filters on old-timey flatheads like my Hudson Big Six. I'll talk a little about why you might want to use one and respond to some of the back-and-forth discussion you may find on the subject.
</p>
<img src="https://nextcloud.53hor.net/index.php/s/rqJmkBTj8S63AN5/preview" alt="Hudson Fram Ad" />
<p>
I really like to drive my car. I like to think I'm one of the youngest Hudsonites with the most miles put on his Hornet per year. That means that throughout the restoration process Dad and I were always looking for modernizations or upgrades that could extend my mileage, increase safety, and improve reliability. All while keeping the original drivetrain in tact. One of the simplest modifications was the addition of an oil filter.
</p>
I confirmed I have no additional orifice restriction on my bypass filter system. I think I have done enough reading to write up my thoughts on this. My reasons come mostly from the 1952 Mechanical Procedure Manual:
Oil pressure is regulated by a built-in nonadjustable release valve and spring accessible through a plug at the left rear side of the engine. When starting the engine the release valve has moved to a position that closes the oil passageway to the oil filter and allows full pump flow direct through the main oil gallery extending the full length of the crankcase.
I think over time it's possible for this release valve to wear out, and during restoration some folks may eliminate it. This release valve, when it's doing its job properly, should prevent engine oil starvation due to the filter. I do not see a good reason for arbitrarily increasing the pressure with an orifice restriction. The reason has got to do with oil pressure versus oil flow.
No flow at all due to blockage results in the greatest level of pressure in a system. There are cases where a gallery or orifice blockage (a spun bearing perhaps) can cause oil starvation/low flow to a component when pressure is still good, and no oil dummy light gets lit. What's important is that oil flow is at all times adequate to lubricate the entire system. If the release valve in the block is functioning, it should allow for good flow despite the presence of a filter. Increasing pressure when flow is good may be a no-op.
Oh, and the same book mentions:
On cars equipped with oil filters the cartridge should be replaced at 5,000 mile intervals or when the oil shows evidence of becoming dirty.
I'm not saying this is their recommended oil change interval (1000 miles, also in this book). But I do know there is some skepticism on the effectiveness of even modern filters and whether or not the original units were Hudson-endorsed or a sales gimmick. I just wanted to include this as a light indicator of Hudson's trust in a filtration system of any kind. Much of the information in this book may have or has definitely changed over time, but I still think it's a great technical resource.
Whew, anyway, that's my full thought process. As always, the choice is yours!
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