Now that the pistons and barrels are safety attached to the crankcase it was time to seal it all up with some refurbished heads! The original barrel-heads were stripped, then sand blasted some time ago now, so it was just a matter of fitting the new parts (valve springs, spring seats, valve guides, cotters and inlet/exhaust valves). The process started with a complete chemical rinse out of the head, shortly followed by a thorough power-washing outside. That was the easy bit. Next was to cook them up on the heater to a temperature of around 150 degrees to allow the head to expand in order to accommodate the new brass valve guide. To make sure the interference fit went smoothly the guide was put in the freezer to cause the metal to contract. Once both were at their alternative temperatures came the moment of truth, a one chance only bash to get the guide into the barrel head. The guide was put on a fitting tool, and sprayed with nitrogen freezing spray to shrink the brass and then quickly aimed over the hole, then with one (several) smash with a hammer it slotted directly into place! After everything cooled down the final step was to insert the valve stem and fit all the remaining components. The last picture shows all the original grubby parts that came off the head when I first stripped the engine down.