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Author Topic: Oil Filter Adapter  (Read 539 times)

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Oil Filter Adapter
« on: November 09, 2019, 02:38:09 PM »
I am working on my all stock 77 "B". It came factory with the spin on oil filter adapter I'm thinking? Filter canister points up.

I don't remember how I came to the decision, but I'm using Wix PL20195 filter which is a little longer than the filter listed for the car.

The filter is listed with a "drain back valve" just like the shorter one, but when it sits for a while, like our cars often do, the oil in the filter drains back into the motor, and it takes an inordinate amount of time to fill the filter back up, to get oil pressure. I'm always very careful to keep the rpm very low until I get pressure, but I don't like it. The question is do all filters drain back over time, or is a check valve or something missing from my car? I'm going to change back to the short filter to speed up the time it takes to get pressure, but was just wondering what the deal was.

Bob Morgan


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Re: Oil Filter Adapter
« Reply #1 on: November 09, 2019, 02:59:50 PM »
The filter body points upward because there was no physical room for one to be installed in the traditional downward orientation. My 1980 is the same. I use the standard "Classic Gold" oil filter provided through Moss dealers. They too have an anti-drain back valve. I have near instantaneous oil pressure upon cold start --- even after letting the car sit for weeks.

The has a tube designed to hold the oil in a short filter. The longer filter drains down to the level of the tube and has to be refilled each time. That's why the short filters get instant pressure.

Tony Thomas
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Re: Oil Filter Adapter
« Reply #2 on: December 17, 2019, 12:34:22 AM »
Over the years there's been a lot of discussion about the filter height.  With the filter facing down, this is less of a concern.  It actually adds some capacity to the system.

Facing up, the filter operates differently. The adapter is equipped with  a standpipe designed to retain oil in the filter and reduce 'dry cranking' that happens until the filter fills and the pump generates pressure throughout the engine. 

if the filter casing is significantly longer than the than the standpipe, even with a functioning 'anti drain-back' type filter, you end up with an empty gap between the end (what would normally be the bottom) of the spin-on filter and the top of the standpipe tube.  Oil pressure and flow in the engine will not begin until that space is filled.  The taller the filter, the more space.  That time cranking without pressure can cause wear and damage over time. 
Shorter filters are generally considered better for this application as a result.  The filter height should be somewhere in the 3.75" to 4.25" range.  Examples of these shorter filters are the Purolator PL20081 (3.75" height/3.77"diameter), Fram PH43 (4.05" height/3.66" diameter) or  Wix 51068 (4.338" height/3.66" diameter).  There are others and lists that can be found on the web. 

The site does show the measurement and capacity specifications as well as cross references alternatives to the filter you've chosen.

Hope that helps you.

Safety Fast!


Art Isaacs
AMGBA Tech Staff


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