No Yttrium
 

Porsche 911 air-cooled cylinder heads DO NOT have Yttrium in them. Saw this on another forum:

"We've learned that Y is for "Yttrium" and this was used to add temperature robustness to the heads. Does anyone have any documentation that these were, in fact, unique to the 2.4S? Some suspect marketing department hype, i.e. that all heads are made from the same material, that is T, E and S?"

Y-alloy is the name for a specific Aluminum alloy. The name comes from Experimental series "Y". The composition is:
Aluminium Balance
Copper 4.0%
Nickel 2.0%
Magnesium 1.5%

The heads will have a Y cast in them if they are made of Y-alloy. The other common alloy is RR350, which is used on turbo heads.

I was looking for information on welding castings made from either of these alloys. Has anybody had any experience?