Where the inlet manifold (bit between the bottom of the carb and the block) attaches to the top (right) of the engine, there is a water channel through that. If you take the carb off, it is held on with three (I think) bolts. I had a bit of trouble finding the right replacement gasket, luckily it came off in one piece, so I cleaned up all faces of gasket, block and manifold and very carefully applied red hermetite, seems to be working ok ish.