What is this on my oil pan?

[busmania]

I swapped oil pans because mine had a small pinhole from rust. Anyway, the pan I took off my spare engine has this fitting. At first I thought maybe something to do with a full flow system until I took the pan off. It seems to be threaded on the outside but no hole through coming into the inside of the pan. What is this?
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[Bored&Stroked]

It is an oil-return line for a "drip feed" type oil filter - like the old Fram filters that mounted on the Driver's side head. It is NOT for a full-flow system!

There is an outlet on the bottom of that round steel "plug" you see inside the pan.

[cadillac512]

Is there a relieved area on the inside (like a small slot) aimed downward? If so, it's oil return from the filter.



Terry

[Terry,OH]

Originally they were not drilled through unless the oil filter was added. The filter was an optional accessory.

[jimTN]

That is where you get the "restriction" for oil flow.

[marko39]

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Originally Posted by jimTN

That is where you get the "restriction" for oil flow.

The restrictor should be on the filter inlet, this is not intended for that purpose.

[busmania]

Originally Posted by cadillac512

Is there a relieved area on the inside (like a small slot) aimed downward? If so, it's oil return from the filter.



Terry

Apparently there is a very small hole on the side I can’t see.

So do I need this or can i plug it? Is this the stock spot for the oil return on a 40? It wasn’t on my old pan.

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[Mart]

The outlet is at the bottom so the oil dribbles down the side of the pan, rather than squirting out across it and possibly hitting the rotating crank and rods.

I don't think the only drilled out when a filter is fitted comment is correct, neither do I think this fittings provides the restriction.

It's a handy thing to have though, because it is sometimes difficult to route a pipe back to the pan.

You can plug it if you are not using it. It is a 7/16-24 thread. If you cut off and roll over a piece of 1/4" tube and hammer it flat you could use a piece of brake (or oil) tube to blank it off.

Mart.

[cadillac512]

Mart is correct.

[Als48]

Or you could place a rivet in the fitting rather than tubing. Then grind it flush. It would look (almost) original. It was once possible to purchase a blind plug for that sort of purpose, in brass. Swagelok and Imperial Eastman brands come to mind. I worked with a lot of tubing/piping installations in the plant I retired from, which utilized huge numbers of air-operated instrumentation/valving and controls. The plant was originally built in 1952 with WWII technology. We were constantly adding and changing old systems to update and improve them.

[Terry,OH]

It is not the proper location for the 1940 oil return line from the oil filter You can block it with a pipe plug.

[jimTN]

I just started an engine I put one of those pans on and added a oil filter. No special fittings. It holds good oil pressure. 40 at a fast idle.

[JayChicago]

Originally Posted by jimTN

I just started an engine I put one of those pans on and added a oil filter. No special fittings. It holds good oil pressure. 40 at a fast idle.

The .062 restrictor on the inlet side of the oil filter reduces the pressure going into the filter. The filter media would further reduce the pressure reaching the outlet side of the filter. I would think the return line to the oil pan would have little pressure, almost a gravity return.