As I said in the last page the first pour was short of metal so the risers/feeders didn't fill high enough to do much good. The result was that the finned areas didn't fill and there was a shrinkage cavity near the combustion chamber.
One the next pour I preheated the mold using the furnaces spill hole as a heat source. The mold was changed a little for the second pour as well. The changes were...
Adding more material to choke.
Increasing end taper of the fins. (Side taper is fine)
Reducing riser dimensions so that less material is required.
The risers will actually serve a purpose for machining as they will give me some places to bolt the casting down while the combustion chamber side is machined. The combustion chamber side of the mold has .2" of extra material on it's face. This allows for any casting defects to be milled away.
The "JCI" combustion chamber shown here is .70" deep. Once this side sees the face mill it will only be .50" deep. The shrinkage area on the side is less pronounced on this pour due to mold preheat. It's my belief that filling the mold completely will snuff this problem area out. One other theory is that I should have made the gate entrance somewhere away from the combustion chamber plug. After doing some more reading I found that gating should avoid obstructions like this.
Let's hope that the next pour will be flawless.
