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Discussion Starter · #1 ·
Hello All,

I've been looking at this hole for a while now, but I keep forgetting to ask about it. I first saw it when the block came back from the machine shop. The block was so unbelievably filthy when it was removed that it doesn't surprise me I never noticed it until it was clean. It's on the looker's right side of the block, behind the timing cover. Fishing an engine brush through the hole indicates that it's connected to the oil passage that supplies the first cam bearing. I cannot remember anything being in that passage or coming out of it when I pulled the engine out and disassembled it. I went back through pictures I had of the removal and various steps of the disassembly, while none clearly show the area, nothing appears to be obviously near it either. Vehicle is a manual trans, and does not have an oil cooler.

What is this passage for?

Thanks,
T.P. Crockmier

Mystery Hole.jpg
 

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Where the oil galley was drilled. Some are plugged some use it for a oil pressure sending unit instead of in the back of the block. Good pipe plug is all it takes. But use it to clean your oil galley. Never trust that the machine shop cleaned your block. I've found lots of garbage after they "cleaned it".
 

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Discussion Starter · #4 ·
Where the oil galley was drilled. Some are plugged some use it for a oil pressure sending unit instead of in the back of the block. Good pipe plug is all it takes. But use it to clean your oil galley. Never trust that the machine shop cleaned your block. I've found lots of garbage after they "cleaned it".
That’s pretty much what I was thinking. I wasn’t too concerned and was going to get a plug for it, provided it wasn’t a feed for something crucial. And yes, after the block came back from the machine shop I did use an engine brush kit and went after the oil galleries with rubbing alcohol and then clean engine oil to remove anything left over from the hot tank.
 

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Clean the cylinders with papertowels and ATF, you'd be surprised what you find.
 

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Be careful, some of those plugs are J thread which appears to be pipe thread but it is not. Only way I was able to find the correct plugs was to order a complete freeze plug kit from my machine shop with the galley plugs in it.
 

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Discussion Starter · #8 ·
Be careful, some of those plugs are J thread which appears to be pipe thread but it is not. Only way I was able to find the correct plugs was to order a complete freeze plug kit from my machine shop with the galley plugs in it.
I had some spare gallery plugs hanging around from this project. I found one that threaded in and would tighten up, put some ultra black on the threads and snugged it up. Seems like it should work.
 

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Make sure plug u used seats at TOP of hole, not bottom, or oil flow and scored bearings
will result -ask me how I know!
 

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Discussion Starter · #10 ·
Make sure plug u used seats at TOP of hole, not bottom, or oil flow and scored bearings
will result -ask me how I know!
I'll bite. How do you know?

Secondly, when you say the "Top" of the hole, are you able to clarify that a little bit more? The plug I used had a slight taper at the business end. One of the things I checked, and looked okay was the depth of thread vs the depth of the plug. It appeared that too long of a plug would block one of the oil passages, but the plug I used, based on my ultra accurate eyeball-based measurement, appeared to be short enough to not interfere with the passage at the end of the threads. It's not too late to remove and evaluate again, which it sounds like I may want to do that tomorrow.
 

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Sorry, 4 months ago, just notice message. I took out my bearings with wrong plug, sat too deep in hole, takes a special plug, that is all I can remember, will def. restrict flow to entire engine if wrong.
 

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Actually a more bigger picture of the whole part would help. Looks like it's on the head.
 

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Discussion Starter · #13 ·
That's the crank nose in the lower corner of the original picture, and the water passage into the right side of the front of the block up top. The Mystery Hole is halfway up the timing cover on the front of the engine, right behind where the mechanical fuel pump would mount.
 

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Discussion Starter · #16 ·
That diagram does make it easier to see how a plug that is run too deep could cause oil starvation. Bit odd that the plug kits for the engine seem to omit this one. Went to a salvage yard today and pulled one, will post pictures when I am home.

Cheers,
T.P. Crockmier
 

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Discussion Starter · #18 ·
I think it might be the other way around. On the left is the plug I pulled from a similar era 460 at the junk yard, on the right is the plug that I had in the block. I'm convinced that the plug I pulled from the yard is the better fit - it is physically wider and fits the female threads correctly. It snugs up much earlier and tightens up with a thread or two still exposed, whereas the other one would continue to drive into the orifice. Given their shapes and the diagram of the oil passage, I'm far more comfortable running the flatter wider plug. Seems to me that the bevel on the other one would potentially intrude too far into the passage.
 

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I think it might be the other way around. On the left is the plug I pulled from a similar era 460 at the junk yard, on the right is the plug that I had in the block. I'm convinced that the plug I pulled from the yard is the better fit - it is physically wider and fits the female threads correctly. It snugs up much earlier and tightens up with a thread or two still exposed, whereas the other one would continue to drive into the orifice. Given their shapes and the diagram of the oil passage, I'm far more comfortable running the flatter wider plug. Seems to me that the bevel on the other one would potentially intrude too far into the passage.
I would go with your guess. Something I always do also, is take a grinder and get in the passages and round those sharp edges off.
 

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I think it might be the other way around. On the left is the plug I pulled from a similar era 460 at the junk yard, on the right is the plug that I had in the block. I'm convinced that the plug I pulled from the yard is the better fit - it is physically wider and fits the female threads correctly. It snugs up much earlier and tightens up with a thread or two still exposed, whereas the other one would continue to drive into the orifice. Given their shapes and the diagram of the oil passage, I'm far more comfortable running the flatter wider plug. Seems to me that the bevel on the other one would potentially intrude too far into the passage.

The pic on the right is a J thread tapered plug meant to go in the front behind the timing cover.

A typical 3/8" tapered npt plug works well in that threaded hole.









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