Often fuel rather than coolant,from a hosing injector.You will probably never find out exactly what happened.Like mine,yours was "repaired" by someone who didnt know,didnt care - or was told to slap it back together.
Good luck with the rebuild,may I suggest you contact Frida at Turner engineering for the parts when you know what you need,their prices are very fair considering the quality of what they supply.And they use them in their own builds too.Not cheap to do,mine needed an oil pump which is £300 ish,there is no way to make the job viable for a customer.I only bothered as it was my own car,tis a time hungry job.... Shame,I enjoy engine builds.