Engine: Quick Question... Drain Plug Size

[DEEPNHOCK]

Quick question....

What is the drain plug size on a Stude V8 oil pan?
(Late model R2 style, but I think that matters not)

Need the thread size and diameter, and not just the hex size...

(I have a hole to fill)

[BobPalma]

The plug diameter and thread 3/8" X 18, per the parts book. Not sure of the length; perhaps 3/4".

IIRC, the wrench size on the hex is only 9/16" on all pans starting with 1959, and maybe earlier. BP

[Alan]

3/8" Taper Pipe.

[Mike]

It shouldn't be a taper thread, unless someone has modified it. There isn't really a "bung" welded to the pan either. There is simply a hole in the skin of the pan. A nut plate with parallel threads is spot welded to the inside of the pan, with no attempt to seal it to the skin. The plug essentially is a short, fat, bolt with a flange and "O" ring. The flange and "O" ring are supposed to seal against the outside skin of the pan. It's important to realize that the only place any thing is supposed to seal is at the "O" ring and flange on the plug to the outside skin of the pan. Sealer on the threads won't help. A tapered plug won't help.
The flange on earlier plugs is much bigger around, offering more sealing surface, if the pan is flat around the hole. I'm not sure if the early and late thread is the same. I think so.
There's a story that a cart full of early plugs were made with the flange not square with the threaded portion of the plug. When the problem was discovered, the defective plugs were set aside to be re-machined. They set around until the company closed. Some got loose and have been sold as replacement parts; beware.
Mike M.

[StudeRich]

The are no "O" Rings on Studebaker Oil Pan Drain plugs. There is a Flat "Gasket"

[Mike]

The are no "O" Rings on Studebaker Oil Pan Drain plugs. There is a Flat "Gasket"

You're right. Technically, an "O" ring has a round cross section. The seal on the plug is flat, like a washer. It could be called a gasket.
Mike M.