348 Sump Plug Thread Pitch????

[BB1960]

Can anyone help, what is the thread pattern supposed to be.

I looked at it and guessed 9/16, I've tried course and fine (unf and unc) with no luck.

Either the thread is stuffed, or I'm going stupid.......

Any help please......

[tripower]

Can anyone help, what is the thread pattern supposed to be.

I looked at it and guessed 9/16, I've tried course and fine (unf and unc) with no luck.

Either the thread is stuffed, or I'm going stupid.......

Any help please......

I just measured my drain plug from a 1961 348 pan. It measured 17/32" with a 20 thread pitch. I tried a 1/2-20 bolt in the pan and it was sloppy. Also my drain plug has a + cut on the end and then is tapered. Hope this helps.

[BB1960]

Thanks for that. I'll head out tomorrow and pick one up.......

[larry t]

I just measured my drain plug from a 1961 348 pan. It measured 17/32" with a 20 thread pitch. I tried a 1/2-20 bolt in the pan and it was sloppy. Also my drain plug has a + cut on the end and then is tapered. Hope this helps.

I believe that 1/2" is stock. The plug with the + on it is an oversize plug that is used to repair a pan with stripped or worn threads.
Larry T

[BB1960]

Def not 1/2 inch. A 1/2 inch sum plug/ bolt slides straight through the threads.

[larry t]

Check this out. The common oversized drain plugs come in 1,2 and 3 sizes oversize. Most parts stores carry the oversized plugs.
Larry T

http://www.lislecorp.com/tool_detail.cfm?detail=1168

[WENGINE]

Just Checked mine ( 59- 348) 1/2 X 20 tap went right in with out a problem ?