I went with the late style exhaust headers. It's a much better system allowing some play aligning the exhaust system and still sealing. And no more exhaust lock ring or coming loose!

bob, not familiar, could you expand on your post.

Thanks gentlemen, is the alloy ring pressed, heat shrunk, or threaded into the head before it's welded? Graeme

The first step is to clean out the damaged port using a mill. Take measurements, then make the threaded inserts out of round stock. Cut inserts to size, and drop them in. The holes are usually so damaged that once they clean up you just drop them in hole and weld. Most often the head is preheated for better weld penetration. In the case of Tim's head [play on words here] there was amply empty space to fill in around the insert.

Graeme,
Do you use the 750 pipes on your MK3? I've had the balance tube connection on the header break at the weld where it allowed the header pipe to shake loose and I lost the split washer. You don't even want to have that happen. That and the fact the steel nut will eat the threads up as it comes loose.

Tim_S

britbike220 wrote:bob, not familiar, could you expand on your post.

It's a 3 part system used on the 1975 Norton head pipe. The header is bell mouthed http://tinyurl.com/26pka7j with a rounded insert going into the header, a locking ring on the backside of the header the large 850 exhaust nut tightens down on. Just need to order 75 header without cross over. http://www.oldbritts.com/1975_g26.html #8, #31, #32

Haven't had an exhaust nut come loose since!