Not very useful since I don't remember the size. But I found a tap that required just a little larger hole than the I.D of the nipple. Drilled and tapped it for a plug, never had any issues with it.



1972 Barracuda - 5.7L Hemi, T56 Magnum 6spd - https://www.facebook.com/GoodysGotaHemi
2020 RAM 1500
[img]https://i.imgur.com/v9yezP9.jpg[/img]