header stud

does anyone know what size nut is used on the 1600cc exaust header? i'm missing one. it looks to be 8mm but i can't get the correct thread pitch...

thanks.

Just happen to have mine out after pulling the headers for my oil cooler installation.

Studs are 8mm X 1.25 pitch.

Overall length is 1.5 in. with a shoulder in the middle.

BTW: Those should be locking nuts (they have a captive lockwasher on the nut crown)

a long long time ago, when i was a kid i started in a vw engine rebuilders shop. my first job (one of) was to dismantle engines
for rebuilding. i learned the hard way but more often
then not the exhaust nuts and studs became one and when removed with a wrench would round the nut or shear the stud. from then on i chiseled the nuts off, splitting them saving the studs. on my car
i use stainless whenever available.