my friend has a sohc turbo and when his hg went it pushed the coolant to the coolant overflow tank.
you'll know if you did damage to the head - warp damage - when you remove the head to replace the hg if that is what needs to be done. if you did warp the head you may be able to have the head milled to fix it. maybe.
__________________
if you can only race me in a straight line then whats the point 
...91 SMF SCCA
http://www.flickr.com/photos/8341770@N07/5601083432/http://www.flickr.com/photos/8341770@N07/5601083432/ by http://www.flickr.com/people/8341770@N07/, on Flickr
I see people out there spending money on the car to improve it … If you spend half that effort just working on your driving skills, making you and the car work together as a team, then you’ll go faster – period. To make the car go a second faster on the track takes a lot more energy and money than making yourself drive it one second faster.
– the late Tom Thrash SCCA Solo E Production