Fozy,

Forget about the YB0611 - as even with a huge discount it wont be as cheap as the standard late Es Cos gasket: YB1261

These are approx £ 19.00 from PJ Motorsport or your Ford dealer.

Quote Karl Norris:

"The std escos head gasket is YB1261 (the GpA YB0611).

The gaskets are identical in construction with the exception that the the YB1261 has two crimp rings around the oil drains, which helps prevent oil seeping into the gasket around these oil ways.

Power wise both gaskets are suitable for up to 300bhp in std form and 500+ with wire ringing.

The use of either of these gaskets over around 300bhp without wire ringing will result in premature failure as the gasket fire rings gradually get "blown" out making the fire ring oval shaped with eventual failure. Exactly how long it will last is debatable as its dependant on how much on boost driving the engine sees, but expect either of these gaskets at over 350bhp to last less than 10,000miles.
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Best regards,

Karl............Norris Motorsport"