Hi All: I was changing the thermostat in my 1974 slant six yesterday, and something interesting caught my eye. As I peered into the cylinder head through the thermostat opening, I saw two rods - one straight and one curving - in the head. They appeared to be about 1/4" in diameter. They looked like they shouldn't have been there, so I tried pulling them out through the thermostat hole but they wouldn't budge. So I just left them there and finished the stat installation job. The engine runs perfectly with these rods there. Then I recalled an article some years back about these rods somehow being part of the head casting process, and are sometimes (or usually) just left there after the heads are made. So what gives? Why would the factory leave this waste material there? How is it that it doesn't affect the performance of the head? Perhaps it's just me, but it bugs me that these things are in my engine, and I want them out. Your thoughts?