Need help on how to fix a welch plug hole leaking

The plugs come as disc type or cup type, and they don"t interchange because the holes are machined differently - the hole for the disc type has a shoulder. Assuming yours is a disc type, it might be an obsolete size unless you want to buy a box full as already mentioned below. I tried to find some at a very old engine rebuild shop that had more junk than you can imagine, but no luck.
Regardless, no one has actually explained how to install - clean out the hole as well as you can, lightly coat the hole and edge of the plug with sealant, then insert the plug with the convex side out. You then need to peen the convex side down to flat across about one-half the diameter of the plug, which will expand the plug to fit tightly in the opening. Don"t peen the plug past flat, in other words, don"t reverse the convex and concave sides, or you will actually loosen the plug. Hope this makes sense. The rubber plugs work fine for antifreeze, but I"m not sure that will work for you. Sounds like yours will be in oil.

Good luck,

Larry

Diameter may be a big issue for you. I had to replace one of these on my 700, front of the block. No one had a plug large enough. I finally dug around in the archives here and found the name of a jobber in the midwest who sells them - but only in boxes of 100. Someone else on the forum told how they were able to get the guy to send a "sample". They did the same for me.

Let me know if you can't find your welch plug - I'll dig out the contact info and send it to you.

Tim