You could cut a keyway into a washer and tack weld it to the fan. That’s about the only way to salvage this. Original counterclockwise fans are hard to find, but you may be able to find a modern 15mm ominidirectional fan somewhere.
I don’t have a gas welder, only a MIG. While it’s always great to have an excuse for a new tool, it takes practice from what I understand to be able to gas weld (especially thin sheet metal.)
If I had the tools to ensure concentricity I’d try the washer trick. I was thinking that a jewelry welder might be a possibility, but I don’t think the under $250USD models will be up to the job (they’re mainly for spot welding and have no filler rod or wire.)
I’ll see if the machine shop I take the pulley to will have any ideas. I would think I can just use the other undamaged keyway so that’s what I’ll do if I want the car on the road ASAP.
I found this batch of Lucas E-type fans on eBay. Alas, the one that matches my fan is the one that’s damaged. 
But maybe I can use one of the others.
Jaguar XKE E-Type Generator Fans - Lot of 4 Pcs | eBay
Dave
Thought just came to me - if 15mm fans are very common for Lucas alternators, maybe I could use a fan for some other Lucas model instead. Many seem to have the dished center, which I’m thinking is important to maintain proper pulley alignment?
eBay has many more listings of Lucas alternator fans for other models.
Dave
make a jig out off square ply wood with a hole in the centre to line up a washer Use your mig welder to spot weld the washer in 3-4 places then drill , file it out what ever is required
Easy
Hmm. That’s not been my experience. I switched from oxyacetylene to MIG for bodywork and found that the MIG welds were indeed much harder and could actually crack when planished so I switched to TIG, either using the same mild steel filler rod as for oxyacetylene or even none at all with a tight fitment between panels. Then again, my oxyacetylene setup isn’t high quality while my TIG is. I’ve actually had less consistent results with gas welding from the flame drifting either way out of neutral.
Update on this saga: I judged that sending the mismanufactured pulley to a machine shop to remedy the fit issue was impractical - too expensive. The shop I visited said they would have to use a special boring bar and then recut the key slot, which would cost more than the pulley.
It turned out I was able to get it to fit with a few passes of a sanding drum. Only .002" or less had to be removed, and I managed to do this without appearing to affect concentricity. But the slot for the Woodruff key (actually a fixed key on the replica) would not fit. I spent a lot of time filing the slot but was worried I was getting it wrong and close to ruining the pulley.
As it turned out, it fit very well on the original 11AC alternator with a rather beat up Woodruff key, so I gave up and put the old pulley on the new replica, and reserved the new pulley for the old 11AC original! Though I plan to fit a new Woodruff key which might not fit as well - I don’t know if the beat up Woodruff key was the cause or the victim of the cooling fan damaged keyslot.
Anyway, not having been able to find a reasonable replacement fan yet, I put the old fan back on, but used the undamaged key slot opposite of the damaged one. Was it Lucas foresight that supplied a duplicate slot on the fan?
After install, it fired up and seemed to work well, but when I revved the motor above 2000 or so I heard a rattling sound. Uh-oh. I decided to take the time to try to be scientific about it, and took the fan off, then re-installed the assembly.
No rattling sound. Well, I don’t have a spare fan, though Martin Robey lists a reproduction Lucas 11AC fan that looks like a match for my old one. There was no scraping on the alternator, and no blades are loose. So why it is rattling?
But then I remembered that the SNG Barratt repro alternator had this rubber O-ring whose function I didn’t understand. I originally slid it to the base of the alternator shaft, where it was duly crushed by the fan/pulley assembly and probably wasn’t where it was supposed to go.
But what if it was supposed to go between the pulley and the fan surface? So I got another spare O-ring and put it between the pulley and the fan. I tightened it up and reinstalled.
So far - no rattling at 2-3,000+. I don’t know if the O-ring actually had an impact or not. But if this will hold up for a thousand miles at least, I can salvage the driving season. The Robey fan, even if in stock, might not get to me before it’s time to put the Jag away.
Let’s see if I can get a few hundred miles on this and I’ll report back on how it and the repro alternator are holding up.
Dave
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