Inner sactum oil galley plug

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dibbons

dibbons

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It looks like we hot-tanked my 340 block without having removed a "hidden" oil galley plug. I am getting ready to final clean block oil supply lines with nylon brushes. Is it necessary to remove this other plug? If so, does an allen wrench 5/16" fit perfectly? And is this plug usually a bear to remove? If I strip it, I will leave a mess in a very inaccessible area. Thank you.

The fotos shows the plug we did remove, which leads nowhere. The one I am referring to is behind the one removed (at the rear of the block on the driver's side). It's too dark in there to take a good foto.

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BRB Be right back. I need to look for the info on the oil galley plug down in (under) the main bearing threads that needs to be replaced after boiling. Otherwise you "will" have oil pressure issues.
 
I was talking about a threaded plug (see foto where the 5/16" allen wrench is sticking out of the block). Did not even know about this other one toolmanmike is explaining.

I looked for this "secret" pressed in plug and found it still in place, located about 2 1/4 inches below the oil port hole in the block/rear main cap that is fed from the oil pump. I'm not about to remove that sucker. Yes, you do learn something new every day and often times thanks to members of this very forum.

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There's a Welch plug (like a core or frost plug) down inside that seals off a oil passage.
 
dibbons said:
I was talking about a threaded plug. Did not even know about this other one toolmanmike is explaining.
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The plug Mike is referring to is a pressin and that separates the two lines going to the oil filter. Without it you have real crummy oil pressure the other thing is before you replace it. You should take a long half inch drill bit and drill that passage to half inch because it is the main one that feeds your lifter galley and it is usually a bottleneck from the factory.
 
Jadaharabi said:
The plug Mike is referring to is a pressin and that separates the two lines going to the oil filter. Without it you have real crummy oil pressure the other thing is before you replace it. You should take a long half inch drill bit and drill that passage to half inch because it is the main one that feeds your lifter galley and it is usually a bottleneck from the factory.
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Yes. I used to work in a manufacturing machine shop. You can only drill so far in with a drill and limited to the stroke of the machine and the length of the drill bit. Here comes the step drill procedure. The first hole is say 3/8, then you drill a couple inches further with a 5/16 and then a couple more inches with a 1/4. The last (larger) hole also gives the shavings space to exit the hole.
 
dibbons said:
I was talking about a threaded plug (see foto where the 5/16" allen wrench is sticking out of the block). Did not even know about this other one toolmanmike is explaining.

I looked for this "secret" pressed in plug and found it still in place, located about 2 1/4 inches below the oil port hole in the block/rear main cap that is fed from the oil pump. I'm not about to remove that sucker. Yes, you do learn something new every day and often times thanks to members of this very forum.

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Yes, that plug SHOULD come out.
 
If you want to properly clean the block before assembly, ALL the plugs come out. Period. Otherwise there's no way to truly clean all the passages. The 273 I'm working on I had to weld a 6" bolt to that lifter galley plug in order to remove it - the square drive socket on it rounded trying to take it out.
 
dibbons said:
I was talking about a threaded plug (see foto where the 5/16" allen wrench is sticking out of the block). Did not even know about this other one toolmanmike is explaining.

I looked for this "secret" pressed in plug and found it still in place, located about 2 1/4 inches below the oil port hole in the block/rear main cap that is fed from the oil pump. I'm not about to remove that sucker. Yes, you do learn something new every day and often times thanks to members of this very forum.

View attachment 1715111467
Click to expand...

That plug has to come out. It closes up the driver side oil lifter galley.
If you forget to put it back in you will have low oil pressure.
But to get into the galley with a brush to clean the galley you should remove it and the front one under the cam thrust plate to flush out the galley.
 
I can't get this figured out. Not quite on topic.. but can someone explain how this plug being out effects oil pressure? If not in, the oil travels from the pump straight up past the passages to the filter. The oil is not filtered, and the anti-drain back feature in the filter is defeated, but I can't see how it effects pressure. Perhaps there is some air in filter that is not purged until the oil works its way in there ... ???
 
nm9stheham said:
I can't get this figured out. Not quite on topic.. but can someone explain how this plug being out effects oil pressure? If not in, the oil travels from the pump straight up past the passages to the filter. The oil is not filtered, and the anti-drain back feature in the filter is defeated, but I can't see how it effects pressure. Perhaps there is some air in filter that is not purged until the oil works its way in there ... ???
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I am not certain but I believe the plug directs the oil flow into the block. If it is left out the oil can just go into a continuous loop without going into the block and without making pressure. But I could be wrong. I too have trouble understanding this.
 
nm9stheham said:
I can't get this figured out. Not quite on topic.. but can someone explain how this plug being out effects oil pressure? If not in, the oil travels from the pump straight up past the passages to the filter. The oil is not filtered, and the anti-drain back feature in the filter is defeated, but I can't see how it effects pressure. Perhaps there is some air in filter that is not purged until the oil works its way in there ... ???
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If you're talking about the plug between the two lines. If that plug is missing the oil circles back to the filter and so therefore it does not want to follow the main Galley and lubricate everything and build pressure the way that it
should. It just basically circles the pressure between the path of least resistance which in this case is back to the filter because the passage above it is more restricted it backs up makes a little pressure then the oil goes back to the filter back to the pump making a circle so in effect it is just rolling around in those passages.
 
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if that mini freeze plug ain't installed, the eng will run fine & psi will actually be a bit higher as there ain't no filter restriction BUT the eng life will be shortened drastically even with regular oil/filter changes cuz the oil ain't being filtered (the fresh oil does help greatly tho) & the owner will have no idea what caused its early demise until it is later torn down & the missing plug is noted. What Moper said, remove all of em & clean it head to toe several times. maximum attention to detail on every area.
 
OK, I am pretty much convinced I should remove the little non-threaded welch plug under the number 5 main bearing cap (need to think of a way to extract it) and the hex end threaded plug inside near the distributor/oil pump drive (which for now is basically stuck and won't turn-need to figure a way to extract it, too.)
 
dibbons said:
OK, I am pretty much convinced I should remove the little non-threaded welch plug under the number 5 main bearing cap (need to think of a way to extract it) and the hex end threaded plug inside near the distributor/oil pump drive (which for now is basically stuck and won't turn-need to figure a way to extract it, too.)
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To remove the plug insert a rod down through the passage where the oil pressure (or gauge line mounts) sending unit mounts and just tap it out.
I used a long push rod down through there to tap it out.
 
toolmanmike said:
Yes. I used to work in a manufacturing machine shop. You can only drill so far in with a drill and limited to the stroke of the machine and the length of the drill bit. Here comes the step drill procedure. The first hole is say 3/8, then you drill a couple inches further with a 5/16 and then a couple more inches with a 1/4. The last (larger) hole also gives the shavings space to exit the hole.
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That's not quite how they are drilled. I work for an Oem big three company and sharpen those drills for a living. Step drills are all one drill of two or three different diameters all drilled at one time.
Multiple redrills of the same hole would cost way too much and take too much manufacturing time.
Step drilled holes are a compromise to reduce cost and not to oil your engine better.
 
Rapid Robert said:
if that mini freeze plug ain't installed, the eng will run fine & psi will actually be a bit higher as there ain't no filter restriction BUT the eng life will be shortened drastically even with regular oil/filter changes cuz the oil ain't being filtered (the fresh oil does help greatly tho) & the owner will have no idea what caused its early demise until it is later torn down & the missing plug is noted. What Moper said, remove all of em & clean it head to toe several times. maximum attention to detail on every area.
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Robert you just gave a text book example that adequate pressure does not mean adequate volume. Good job lol. But everything I have read is without that plug the oil pressure will be low. It is in the Chrysler engine book written that way. Unless you have some first hand experience otherwise. Lol
 
Without that plug between those two lines. Oil directly from the pump can bypass the filter and go up to the main oil galley.
 
Jadaharabi said:
Without that plug between those two lines. Oil directly from the pump can bypass the filter and go up to the main oil galley.
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Exactly that is his question. yes the oil can bypass the filter but why would oil pressure be low. Here's a page for you. Bottom right pic.

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A couple of the things that can happen with that plug out are:
1 the oil bypasses and goes up to the oil galleys without entering the filter.
2 the oil back feeds through the oil filter and causes the pressure in that area to build up and cause the bypass in the pump to bypass.

Just a couple of thoughts I had.
 
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Jadaharabi said:
A couple of the things that can happen with that plug out are:
1 the oil bypasses and goes up to the oil galleys without entering the filter.
2 the oil back feeds through the oil filter and causes the pressure in that area to build up and cause the bypass in the pump to bypass.
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I think your #1 is correct.

The pressure to both passages to and from the filter would be essentially equal so there is no pressure to push oil through the filter. I suspect it will gradually fill up the filter and passages. The non-filled filter would be a huge air pocket in the system so the oil pressure might well fluctuate until/if the air gets purged out of there.
 
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