Header to H-pipe nuts, what size?

[CobraWannabe]

I have Mac headers and H-pipe, and I was under my car putting on the adjustable clutch cable, quadrant, and FWA, and I saw that both Driver side nuts on my headers are MISSING. I'm surpirised it hasn't leaked one bit from that side. I've been having trouble with the passenger side leaking from one of the nuts coming loose, but I don't hear anything from the drivers side. Anyway, I'm pretty sure they're 18mm, but what coarse thread are they. And will lock washers help hold them or am I wasting my cents on them?

 

[mike93lx]

sorry i don't know the size, but lock washers won't hurt. personally, i'd throw a little lock-tite on the threads and never worry about them coming off.

if you can take the bolt out and swing down to a hardware store, you'll be able to make 100%sure you get the right nut, since they might have been changed from what came with the pipes.

 

[CobraWannabe]

I didn't know the bolt came out. I'm sure I would be a PITA if I tried.

 

[bigsparky]

the factory ones are 16. I know for a fact because I had to go out and buy a 16 deep socket to do it!