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Porsche 356 Oil Filter Adapter, Version 2


In December, 2017, our vendor changed the design of our most commonly used Porsche 356 full-flow adapter (for engines with integral oil pumps), screwing up OUR intended use!

Use this link to jump straight to the issue.

Justification For Full-Flow

Our engines have a screen in the sump - fine mesh on older ones, coarser mesh on younger ones - and tend to get by without a full-flow filter just fine for two key reasons:

However, Richard became a big fan of full-flow filtration because he's lost more than one engine due to crappy fuel found enroute on long cross-country road trips. One of those engine losses was after he'd already installed a full-flow filter! The problem was that the filter internally bypassed! DOAH! (There's a long story about that one, fuel from a Citgo station in Balmoreah, Texas that sold less than 75 octain fuel out of a pump marked 92!)

So, if you're going to have a full-flow system, know WHY you have that full-flow system! Is it for marginally cleaner oil, or is it to save your wallet some pain when things go wrong?

What Filter To Use

If you're using a filter to prevent disaster, you cannot have a filter that bypasses! PERIOD! These are very hard to find.... You want one you can disassemble you can clean and check, so you KNOW it cannot bypass on you! We have one we like, but the vendor changed the design and there are now limited quantities. Formerly we could get a host of colors, including black as seen above, but these are no longer available at as of this writing we can only get red and blue.

What Adapter To Use

Which adapter depends on a few factors, including firstly which engine type you have. Second is if you care that you are using a mechanical tachometer and want to keep it mechanical. Third on the list is whether or not you want only a filter or a more complex system, say for racing or otherwise with heavy heat considerations, in which case you may require a "remote" solution.

The Issue...

For many years now, we've had a great adapter available, pictured above, that simply replaces the oil pump cover, with a simple notch in the third piece and a standard full-flow filter just threads on. It can easily be removed and nobody will know it was ever mounted... And, it avoids having to have hoses and the like. And, best of all, it would take our favorite filter that cannot bypass! Nice!

However, in December of 2017, our vendor changed the design and our favorite non-bypassing filter no longer fits as-is.

AT RIGHT: Here's the new in December, 2017 adapter showing the deeper hole that accommodates the now non-functional tachometer drive gear. This would be easy to fix with a plug and some machining except that the manufacturer performed a completely unnecessary step of adding a machined-in "pressure relief" for a non-existent pressure generated, in theory, from the lone tachometer drive gear spinning in a blind hole. The red arrow denotes that "pressure relief" notch in the left wall inside the bore. Harder to see, the bore has a step at the deepest point, again, for no known good reason, but it means a simple plug cannot fully fill the void.

The problem is that the manufacturer, in an attempt to save people the cost of an oil pump gear to convert from a mechanical tachometer-drive system to an electric one has reduced the maximum diameter of the filter area and so our filter no longer fits! Of course the manufacturer defends their choice, but we say what good is a full-flow filter that will bypass on you exactly at the moment it's doing the job you got it for?!

Of course, the adapter can be machined to make clearance, BUT, the manufacturer changed that dimension specifically because the deeper bore that lets the un-needed tachometer drive gear have a home in the housing comes closer to the filter and therefore, changing the filter diameter, was for them, the solution. If you machine the filter, you'll breach the tachometer drive bore. POSSIBLY a smaller diameter filter is out there somewhere. However, filters aren't marketed by denoting their dameters very often! And, not finding one, we made our own solution by modifying the adapter to fit the filter once more.

Our Solution

We decided to try a plug, but as can be seen here, the plug couldn't quite do the job because of the unnecessary "pressure relief" seen in the image above, indicated by the red arrow.

AT RIGHT: Our plug makes the bore shallower to the limit permissible by the pump gear, but that dang "pressure relief" pocket still a problem as oil could get through it and thereby beyond the plug. So, something more had to be done...

So... The only thing to do that made sense was to go ahead and clearance the filter canister and then weld up the hole from the breach.

AT RIGHT: Here we see the adapter modified and then welded. Because the weld is hard to see in the image, we've pointed it out with the red arrow. NOW we have a solution that works as intended.







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