Read mjs reply again. He found a plug at his local hardware store he was able and solved the issue with.  Might need to look around for the right plug like some auto part stores have a good supply of these type fittings or a plumbing supply etc..  One thing not to do is get metal debris in the oil galley or anywhere else. If your mechanic has shorter ones then that may solve the problem...........

64F100 57FAIRLANE500

It sounded from my mechanic that it might not have been the original. He said if it won't go in further to grind it or he has shorter ones. When I tried to run the tap thru the hole, it hit the lifter before it was able to clean out many threads. Probably three threads at most. When I look thru the access hole in the block, I saw what looks like a bright metal ring in the plug hole. I don't know what it is. Maybe something to stop the plug before it goes in too far and impacts the lifter. I'd like to know what the original should be like. I may have to get a tap with less taper to it so I can clean out more threads unless I find out what the plug should be and shows me that's not necessary.

Brad
Sierra Vista Arizona
1954 Lincoln Capri

Remove the plug. Insert a wire, small screwdriver, etc, into the hole to measure the distance before making contact. Compare the distance to the length of the set screw. I have to conclude that either the set screw is too long (not the original, the threads inside the block have been crossed/damaged, or the size/pitch of the set screw is incorrect. If it's an oil galley plug, there shouldn't be an obstruction that's preventing the set screw from fully seating. If it's the correct set screw, it should not have been necessary to grind the head to make it fit. 

So I tried tightening the plug to get the clearance needed to drop the distributor in but it was tight. My mechanic said to grind down the back of it and screw it in. I did that but it still is sticking out too far hitting the dist gear. Is this supposed to be flush with the block because it won't go in far enough. It's just a quarter inch deep now and screws in just like two full turns. It has a star pattern hole thru it so it seems to be the right one for the engine bit it's in the way. If anyone knows what's up with this, correct part number, size, distance sticking out, etc please let me know. Thanks

Brad
Sierra Vista Arizona
1954 Lincoln Capri

It's good to know it's an Allen wrench head. I didn't really want to remove that plug cuz I didn't want to damage it and not sure how to reseal it. It has some gray goop sealing it.

Brad
Sierra Vista Arizona
1954 Lincoln Capri

"For want of a nail..."

B-rad, aren't you glad you know now? 

Ah that dreaded plug.  I ran into the same issue with my 368.  I always thought it was a Y-Block issue but it must be unique to the LYB'S.  That plug goes into the oil galley.  When I had the motor for my Convertible rebuilt the mechanic replaced it with a pipe plug.  I snapped two drive gears before I discovered the issue.  That plug uses an Allen wrench to tighten it up.  On the back of the block there will be a small soft plug that lines up with it.  Pull the plug, screw it in a little further, and replace the plug.  In my case I already had the motor and transmission in the car.  I had to remove both and unbolt the tranny to get to  it.  I went to Ace hardware and they had what I needed.  I even ground down the head to give myself more clearance.  When I called my mechanic he knew exactly what plug I was talking about.  He was wondering why it had such an odd plug.  Fortunately I have a local parts shop who had the gears in stock..

Thanks y'all. I didn't know if there was a specific amount of tightening that plug needed to be and didn't want to mess it up

Brad
Sierra Vista Arizona
1954 Lincoln Capri

I agree that is looks like an oil galley plug that should be a flush or close to the surface type plug. They are available in various thicknesses. The shop probably didn't realize a distributor gear needed to clear that plug. I did look at a basic picture of the oiling system of a Lincoln Y-block and it does look like there is an oil galley front to back at each lifter bank.?

64F100 57FAIRLANE500

Looks to me like that is a plug on the end of the lifter oil gallery   Just screw it in further