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.

 

[cokefirst]

That looks like the 1955-56 plug. You may have a pan from an earlier engine.

 

[ICON 56]

It's for the 55 56 57 Y Block Thunderbird engine.

 

[Tom Alpers]

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.

From what I have read, yes, there were two different sizes. I have the larger one as in the photo ICON56 posted. My guess is the early 57's used the smaller size from the earlier years and then they switched for some reason to the larger.

 

[doug7740]

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.

Most Thunderbird oil pans have the larger drain plug which requires a 1 1/8” wrench to remove. The small plug requires a 7/8” wrench for removal.

doug7740
1955 Thunderbird Blue