Hi
Could anyone tell me what the diameter and thread form are of the three long studs that screw into the underside of a Domi 99 cylinder head please?
I’ve just bought a head and the two studs nearest the exhaust seem to be 3/8 CEI but a 3/8 CEI bolt doesn’t go in very far, so maybe it’s not CEI? However, the stud hole between the inlets looks a bit different - looks like a coarser thread and it won’t even start a 3/8 CEI bolt. Are all of these studs supposed to be BSW threads, or maybe Whitworth?
I’ve ordered the studs from Andover but wanted to get a step ahead while I wait for the bits by getting the correct size and thread form tap to clean out the threaded holes.
Thanks
Tony
Hello Tony - The thread form…
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The studs are BSF into the head
The threads are indeed BSF. That's the thread used for iron heads and are perfectly OK. When production shifted to alloy heads, they should have gone for Whitworth, but did not - right to the end of Commando production.
One of mine stripped recently, so I had to take the head off for a helicoil. It's a specially long one, not easy to find.
Paul
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Head Threads
See attachment for list of both iron and alloy cylinder head threads.
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Thanks Philip . That’s a…
Thanks Philip . That’s a really useful document. I have to admit that I was really disappointed when I bought my genuine Norton spare parts list to find that apart from part numbers it doesn’t give much useful information. Compared to Triumph illustrated spare parts books, the Norton ones are rubbish. Therefore, that document showing the bolt and thread details is real gold dust.
regards
Tony
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Hello Tony - The thread form of the three cylinder head to barrel studs are 3/8 inch BSF into the alloy head and the corresponding end for the nuts are 3/8 inch BS Cycle. The earlier iron head Dominators may well be different. Regards, Howard