1957 oil pan drain plug size

[Jimi A]

Are there two different size oil pan drain plugs for a 312 Y- block? I ordered one and it's too small. Why would mine be so much bigger? Any advice will be appreciated.

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[ICON 56]

The drain plug hex head looked abused, so I ordered one from CASCO which shows a 1/2" NPT size. Oops, my '57 is like those shown here: it is a tapered 7/8' thread, and required a not so common 1 1/8" wrench. So, I went out and bought a fairly expensive 1 1/8" combination wrench to add to my collection. I got a flat file out and cleaned up the hex head, and put a new copper crush washer on it.

 

[ICON 56]

This is the wrench I use to remover the drain plug.