Back in 1967, Max Evans Motorcycles, or Caringbah Motorcycles, Captain Cook Drive Taren Point Sydney had 3 Walsh styled heads just like the one you have sitting, gathering dust on the top shelf behind the front counter. I was 13, a Bantam owner, and knew what they were, but the old man said it was a complete waste of time and money to put one on my worn-out '54 Plunger. They were probably sold as scrap when Max moved on. Great video, good luck with the next one and put a bloody respirator on, I've just been diagnosed with Pulmonary Fibrosis, 54 years in the building trade which has cut my life short.
Lost foam is trash. Make a plastic epoxy mold and then cast wax castings. And do lost wax in the sand. When you pour do it so the fins are down, and make sure you have a vent tube not just a pour tube.
A German company doing castings would have poured the material, be it steel or aluminium into a trough and let it fill the mould from below. I saw many casting made this way and witnessed dye penetrant testing after the casts had cooled, very rarely were there defects.
When casting, especially with foam which will gassify as it burns away, you must have additional vents to allow the gas to purge. you were lucky the molten aluminium didn't plume out violently. Do please be careful.
I have just played a little bit with lost foam and lost 3D printed pla. a really thin coating of plaster of Paris on the foam and it made for a very smooth casting.Maybe that would help with the thin fins. Best of luck to you! Keep it up!
Looks like you need some help. I have tried this numerous times, I was getting very close after ~ a dozen times, changing things to de-gassing and gave up! That is what you should do, face the music and go green sand and split mold, that is how it was made. I'm going to be short, because seems no one listens to me, contact me if you have questions. Bentonite clay, sharp sand, and locking boxes. I would first attempt it by cleaning the head really clean and rub baby powder into the surfaces, then sprinkle more powder, and pack the sand. The next way is to make it out of Maple wood, make it smooth, and seal it, smooth it again, powder, then pack the sand. With all those fins, I would put in lots of Bentonite and let the two halves sand forms dry before pouring. Sometimes, one has to admit that this is the wrong road. But, I still get drawn it, hoping someone has really figured out lost foam.
When I used to lost form cast we were taught to have a runner (to pour into) and a small open riser to let gas out. Nice job though, get the temperature right at the gas out, should be sweet.
Comments about needing vents are probably by people who have never done lost foam casting. I'm sure they are suggesting this based on lost way casting, something very different. With lost way casting the model and the vents are burnt out before the pour. That is not the case for lost foam. Any vent channels would still be filled with foam. Lost foam relies on the plaster to be porous to gas so that it escapes to the unbounded sand.
One idea I had is where there are those 4 circles on the head mold where I assume holes will be drilled for head studs, you could put little "spot drill" divots so you have something on the casting to locate the center points of the holes. Or maybe that operation is trivial.
