valve tip broken off

Hi all, This is my first post having just joined the forum, which looks like a great source of information for this engine.
I live in the UK and have a Cobra kit with a 1970 429 in it which is relatively rare over here so not much knowledge to draw on.
The engine was rebuilt for me in in the USA and I shipped it over to the UK a long time ago, having recently gotten the car on the road I was experiencing a loud ticking noise in one head so I took the rocker off to inspect. After a lot of inspection I was really surprised to find one of the valves has had the top 1/4" shear off ! I found a small perfect disk in the oil next to the valve.
I have to assume the valves are actually made of more than one piece of metal or this is the most unique failure I have ever seen.
Is this a known fault on 429/460 engines ?

Thanks
Paul

are you sure that's not a lash cap ? send picture

What kind of valves are they? Some Ford engines did indeed use a two piece valve, but it was commonly the valve head that was welded to the stem (stock steel valves).
These were often used with very "soft" spring pressures for low rpm, low stress applications.
But when they were hot rodded or raced, the valve head would break off and generally destroy the whole motor...ouch!
Many stock 2V Clevelands were like this. They used a weird type of "multi-groove" valve and keeper that held the valve kind of loosely so it would rotate during operation, and thus provide longer wear life for the valve and the seat....it was not one of their better ideas! LOL

I have witnessed the hardened tip breaking right off an exhaust valve on a customer's head with an aluminum head SCJ  so, it certainly can happen if the exhaust valves do have hardened tips.
It was about .100" thick though, not near 1/4 inch.

It sounds like to me that it broke off right at the keeper grove. Normal valve tip length is .250" with performance valves. Any way, you've got to R&R the head to solve the problem and when you do, you can figure out the true failure.