Bypass oil filter question

Ritzy1

Ritzy1

Senior Member
I'm trying to understand how the original bypass oil filter works on my '48 59A-B. So, I see there is a restrictor in the fitting on the supply side of the filter canister and two opposing similarly-sized holes in the stand pipe that the cover bolts to.

Does the oil get forced through the filter from the input line, then fill the canister and somehow get forced through those two small holes and into the stand pipe where it drains back to the pan?

Thanks, Dave
 

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No real forcing involved, it arrives via the inlet pipe, passes through the filter and drains back via the two holes as you said. Once the oil has passed through the initial restriction, the pressure shouldn't get any higher. having the restriction on the inlet keeps the pressure down in the canister and makes it easier to seal. It also stops the filter lowering the available oil pressure in the engine too much.

Mart.
 
Thanks Mart. The holes are so small that it doesn't seem like they'd flow much oil. Seems like it would be more like a drip than a real flow.
 
Remember, there's anywhere between 25 and 60 psi pushing the oil through a .060" orifice. That can be quite a bit of oil in a short time. It would be a small stream, not a drip.
 
Ritzy1 said:
Thanks Mart. The holes are so small that it doesn't seem like they'd flow much oil. Seems like it would be more like a drip than a real flow.
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In a measured test, I found that 5 qts. of oil passed thru the filter every 11 minutes with the engine idling.
 
^I would have to agree. I have one of those beehive filters on my roadster and it gets quite warm. If it was not flowing oil it would not get warm. Interesting that you were able to measure it.
 
51 MERC-CT said:
In a measured test, I found that 5 qts. of oil passed thru the filter every 11 minutes with the engine idling.
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Thanks. That's more than a drip then! It's been a bit of a challenge trying to space the filter off the finned aluminum heads, but I guess it's worth the effort. Lot's of opinions on filter/no filter, bypass/full flow, etc., etc.


I'll be sticking with what it came with, except I'll actually put a filter in there. There was no filter element in there when I opened it up. No wonder there was so much sludge throughout the motor!
 
Mart said:
^I would have to agree. I have one of those beehive filters on my roadster and it gets quite warm. If it was not flowing oil it would not get warm. Interesting that you were able to measure it.
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There was a shut-off valve installed in a temporary return line, then with the engine idling, a measured amount of oil was collected while the length of time to do so was noted. This was done 3 times to get an average time, then a little math to determine how long it would take for 5 qts. to flow.
 
I have not seen inside those oil filters.

But I guess there is a spring and maybe a plate to push and seal the filter in?

The reason for asking, with the engine running and you cracked the lid a bit, would oil pump out the top ?

Or does the oil drain as quick back to sump under gravity because there are 2 holes out and only 1 in of the same size.
 
pooch said:
I have not seen inside those oil filters.

But I guess there is a spring and maybe a plate to push and seal the filter in?

The reason for asking, with the engine running and you cracked the lid a bit, would oil pump out the top ?

Or does the oil drain as quick back to sump under gravity because there are 2 holes out and only 1 in of the same size.
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Yes it would pump out of the top. Source, I've forgotten to tighten the bolt after changing the oil!
 
Looks like the original supply and return lines are flared like brake lines. Could I make new ones using 3/16" line and fittings and a 45 degree flare?
 
Ritzy1 said:
Looks like the original supply and return lines are flared like brake lines. Could I make new ones using 3/16" line and fittings and a 45 degree flare?
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In the past I have purchased 1/4" steel brake/fuel lines of the appropriate length that already have the inverted flare and nut installed. NAPA generally has a good selection. ( Of course they have to be bent to fit )
 
51 MERC-CT said:
In the past I have purchased 1/4" steel brake/fuel lines of the appropriate length that already have the inverted flare and nut installed. NAPA generally has a good selection. ( Of course they have to be bent to fit )
Click to expand...

Thanks. Didn't even think about that, easier, option. I was just thinking I'd make them up from the left over brake stuff I had.
 
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