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MG MGB Technical - Unleaded inserts - How to tell?

Popped the valves out of my head today to put in the new springs and whilst I was at it I had a look at the valve seats.

How can you tell if the head is unleaded? (I'm informed by Ivor Searle the head is unleaded)

Looking at the seats I couldn't see anything obviously 'different'. In fact it all looked like a part of the head casting.

So how can you easily tell?
K Goldup

You should be able to see the line where the insert meets the head- either from the valve seat area or from inside the port about 1/4" behind the valve. This just tells you there is or is not an insert, not what metal it is. Valves should be stellite.
Art Pearse

The factory "unleaded heads" were merely hardened around the exhaust valve seat area. This tended to last only a short time, however. As Art has mentioned, there should be a very distinct line marking where the unleaded after market seats have been installed in the head. If you can't make out the inserts, your head is only a factory "unleaded" head. When I had unleaded inserts installed in my cylinder head, I installed them in the intake, as well as the exhaust, seats. RAY
rjm RAY

The UK never had 'unleaded' heads from the factory. You should be able to see the line of any insert, but then you still have no idea what the insert is made of.
PaulH Solihull

I found this youtube where they test the hardness using a tool.
Is it possible to case harden a valve seat effectively.

http://www.youtube.com/watch?v=9tlsq2ESQz0
c cummins

Would very much doubt whether case hardening is a goer. Case hardening is usually used on low carbon steels and increases the carbon content of the surface of the seel, allowing it to be hardened and tempered. All that heating and cooling!!!!! Not good unless you want to wreck the head. Cast Iron already has a high carbon content, 3.5% plus, (most of which is in the form of free graphite at the grain boundaries) and is quite hard on the surface after casting, this is caused by the chilling effect of the molten metal hitting the mould. Once the suface is machined off so is the hard "skin". Maybe the factory chilled that area when casting or locally heated and quenched the seatings after machining.
If you can detect inserts, they are "probably" hardened. What would be the point of going to all that trouble and expense to put "soft" inserts in. Especially if it was done in the last 15 years or so.
Allan Reeling

This thread was discussed between 10/07/2011 and 18/07/2011

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