It looks like the Jaguar OEM ones are around $25 and the aftermarkets are around $17. The seats seem easy enough to find... not sure if they are OEM.

 

32 x $25 could get expensive... that's $800 for new valves alone. Probably not worth the $$$. Maybe just doing new springs is the way to go... if I can find them new.

 

Have you tried here;
https://www.jaguarclassicparts.com/u...s-4-0-litre-v8
May not be what you want.
When I replaced the Head Gasket on my ‘40 AJ6 I gave the valves a VERY light lapping and they seated nicely, can’t see why the V8 should be much different, they are a marked improvement on the XK 3.4 engines valves that I am setting up at the moment. Just remember if you strip the head down you need to keep the relevant shims with the valves.

 

Sorry about the abbreviations without explanations it is a bit confusing!

JTIS-Jaguar Technical Information Service. The workshop manual for us regular people.
JEPC-Jaguar Electronic Parts Catalog-This is what the dealer parts guy is looking at when you order parts. The drawback is our version is static so you can't see what it's been superseded by. This is usually no problem because the dealer can tell you what the current part number is.

Both free on this forum and yes old software. I still run the JTIS on WIN10 in compatibility mode fine but yes the PDF stuff is better nowadays.
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I'm taking the heads off soon because I found the 12MM Ribe Bit Tool on eBay. Anyone have any pictures or details relating to rebuilding the heads?

I need to replace a few valves and a few springs if not all of the springs.