Stainless exhaust collars

[Oli Hulme]

I bought one of these to replace a chromed/bronze one that had to be destroyed to remove it. It only screws in about halfway, and then sticks. I've tried on three different heads, and it's the same on each. My remaining Bronze collar screws in just fine. Do the bronze collars wear, making them easier to put in? Or are the thread sizes variable on stainless ones? ~Or are they simply tight because they are new?
All advice gratefully received

[George 350]

Hi Oli.
It suggests that the thread is not parallel on the stainless nuts. Can you measure the thread diameter at the beginning of the thread and closer to the plain section? This would give you a clue as to why it is jamming.
The other scenario is whether the thread pitch is correct or not. Laying your 2 nuts together and holding up to the light should show if the pitch is correct or not.
Hope this helps,
George