Water drain tap

[TOMO28B]

Hi all,any idea of the thread size of the drain tap at the back of the engine, on a 1098cc ,1968 moggie.I only ask as the tap will not move and appears to be seized,i don't want to unscrew it from the block or try and give it a bit of wellie yet until I have a new one to go on. I have seen plenty for sale,but am not sure of it's thread size. Thanks all

[philthehill]

The thread is 1/2" x 20 TPI UNF.

[TOMO28B]

Thanks