Hi Guys
Noticed today when removing gearbox that my XF head has GAS stamped on the back of it. Is that something head rebuilders do ? if so what is it likely to mean internally? The car is no longer gas , petrol only when I bought it. 761A stamped on the front
cheers

Some do, not a Ford thing. Gas heads have harder valve seats & sometimes better valves. Ford did a Gas head for BA'S later heads are the same except for turbo. From memory it was L for gas & T for turbo stamped on the R/H front. Regards TPVM.