head gasket on corsa gsi

[tinagamage]

I've just done a head gasket on my Corsa gsi due to a water leak in the gasket i replace the gasket the valve stem seals and cleaned the head ect, it starts first time but after taking her out for a test drive she smokes badly after removing the spark plugs and noticing oil on the pistons i re did the gasket and valve stem seal ect but used vauxhall genuine part but its still the same anybody have any ideas??