Hello, are you actually getting valve float?
Reason I ask is that we had problems with the st springs and I was advised at that power level they would not be required.

The price of thick head gaskets is very high and should anything go wrong you may end up buying more than one hence I now believe its not a good way to go, I would sell the st engine and put decent rod and pistons in the standard engine.

good luck finding a solid focus cheap, out of the 4 I have bought 2 were rotten 1 was good and the last I have not looked at yet. Funny though the best one was the cheapest at £90 so it is possible

Thanks