Confirming exhaust nut size/type for headers...?

[Danny_Ocean]

I'm about to re-install the headers on my '72 2.4.

Are the exhaust nuts M8x1.25? 12mm or 13mm wrench?

Copper? Copper coated? Zinc? Integral lock washer?

[Chilling in VT]

The nuts are M8x1.25 with a 13mm head size. When I did mine last spring, I used a combination of copper coated nuts and the barrel type nuts. When you do it, do yourself a favor and get one of the sockets that has the swivel built into it. Some of the nuts are in very tight spots and the regular socket on a universal swivel will be too tall to get in there. I also used a small amount of permatex ultra copper on my gaskets. It helped hold them in place and also helped to seal the headers to the heads. Make sure you use some copper neverseize on the threads before you put the nuts on. Other than that, it's pretty easy. Good luck.
Joe

[Danny_Ocean]

OK, but...when I try to run a M8x1.25 die over my old studs, it comes to a stop after 1/2 ~ 1 turn. I purchased some M8x1.25 nuts and they go on, but the die won't chase the threads...I even purchased a new die, thinking that my (el cheapo) Harbor Freight die was mis-marked...same problem.

x2

[Chilling in VT]

I have found that sometimes a die will cut deeper threads than some factory studs and bolts. This could be the source of you binding. If you have an 8mmx1.25 tap, place it along side the threads on the stud and eyeball the fit. FWIW I cleaned my threads with a small wire wheel on my dremel tool. Good luck.
Joe

[KTL]

The die is trying to cut square threads and your studs are typically rolled threads which are tapered

l_l try putting this shape

\ / into a tapered shape like this and tell me what's going to happen



M8x1.25 is the right pitch and 12 or 13mm is fine. Sometime 12 is better because the socket is thinner and can get into tight places. I think a thin deep 12 can fit in the hole in SSI header heat shrouds and then you're not forced to use the barrel nuts if you don't want to?

[Danny_Ocean]

Mystery solved. It appears the previous owner (Bubba) did a heli-coil in one of the exhaust stud holes. Does Bubba do the right thing and find the correct heli-coil? Nooooo...Bubba goes to the hardware store and purchases an SAE heli-coil/stud (measurements indicate 5/16 x 20).