Bonnet latch mechanism

Whilst the car is at the painter’s, I’m going through fasteners to clean, blast and plate those that I want in passivated black. I have a question regarding the bonnet latching pin nuts.

The bonnet latching pin is the long pin that comes down from the underside of the bonnet and engages with the latch on the body crossmember. It has a pointed tip, which is slotted for a screwdriver for adjustment. It is retained to the underside of the bonnet assembly by two 7/16" UNF locknuts - see Viart p.350. The book shows these to be plain nuts with a spring washer inbetween.
I’m sorting through the carefully stored fasteners, and the top one of these nuts, although loose in the bag, has marks on it that spell failed spotwelds to me. Should this nut actually be spotwelded to the topside of the assembly (the other way up from in the photo), so the pin just screws into it to set adjustment, and is then held in place by the lower locknut? Has mine come ‘unwelded’, or is this just an odd-looking nut?
Photo attached - I can’t examine the panel it might or might not have been welded to as it’s away at the paintshop.

edit - yes, I know this nut should be body colour.

Not having a 140, but having seen those nuts on other cars, I can only say yes those are failed spot welds.

Mine was welded and interestingly there was no screwdriver slot on the end of the cone, but I added one .

Thanks both - yes, I think it should be welded. Better get it repaired before the painter gets on to the loose parts.

Edit - I just found my backup photo for the parts to be painted, and enlarging the latch panel shows the hole clearly where the nut should be:

I think the edge of that hole shows the matching marks of weld failure, unless Jaguar used a bizarre anti-rotational pattern. Which I’m sure they didn’t. It also shows I need to sort the front edge before it gets painted, too…

Well, the spot welds are a sort of anti-rotation scheme. Anti-drop-on-the-floor scheme too. :grin:

Hi Roger,
Back in September ‘20, you, myself and others had a discussion of the 140 bonnet component colours, and someone reported the latch plate and the vertical air splitters behind the grille were painted black. This would imply that that nut was also black. ( the find this thread, use the search terms: “air splitter”).
This idea is consistent with the practice seemingly used in XK120 parts colours identification, that generally parts bolted to the car after the body was painted, are usually painted black.
So I went and painted these components black, on my car.

However, in view of the picture on page 42 of Porters 3rd edition, the latch plate and air splitters should be body colour.

I am now thinking I should repaint these components body colour, as you are presently doing.

Do you have any further information discounting the idea that the latch plate and splitters should be black? Thank you.

Hi Gary,
Sorry for any confusion - that edit was in error, brought about by not having the parts in front of me.
As in the earlier thread, on the evidence provided by my car alone I am painting all these parts black. Whilst I was prepping them for paint, the old black paint was coming off in flakes as it had no primer beneath it (typical '50s and '60s factory chassis treatment - just blow black over bare metal). There was no ‘key’ for this paint, the exposed surfaces being shiny and smooth steel which had never been media blasted. Having restored so many British sports cars over the last 45+ years, I trust my own judgement on this - my car had only ever had one poor respray, with no removal of the original Carmen Red beforehand, in metallic maroon sometime before it was laid up in 1982 and I am certain that these parts had therefore always been black, applied over bare metal. I am painting them all black.
As Rob intimated in the other thread, everything bolted on to a painted shell would have been black.
I have to emphasize that this my opinion, based on my experience, also with the caveat that it is more than possible that Jaguar changed the process with later 140s. My car, 1955 LHD 140DHC no.499, is relatively early, I think.

Edit - in this thread, it was the weld that I was focusing on. It had slipped my mind that of course all these parts are at the painter’s, as they are doing the chassis black parts for me as well as body colour. Hence the confusion over the colour of the latch plate with welded nut - I was looking at the wrong reference photo.

Thank you Roger for the clarification. My car, S818919DN, is apparently a relatively late ‘140, from September 1956.