After looking at the heads I was wondering how the molds are able to contour the ports then they are able to remove it after the mold? Never really knew how a real sandmold worked... Anyone have any more details?

 

I'm not exactlysure if this is what your talking about but what I have heard about the GM factory in my town what they do is make like a styrofome model of the part. Then they pack sand all around it really tight. Then they pour the aluminum into the styrofome mold and the heat from the aluminum melts the styro away but the the sand keeps the shape some how and then when the aluminum is solid they just knock all the sand off it. That's just what I heard... it could be I don't know for sure.

J

 

Looking at my stock heads, I can see that the head ia made in 2 or 3 layers, then stacked together. That's how they make the passages and machine the inside.

 

That is correct, it is called the "Lost Foam Casting Process". They originally make slices of styrofoam and then glue them all together to form the head and/or block. They are then dipped in a ceramic coating which helps to control the rate of "evaporation" of the foam. This process is used on the I6 in the new Trailblazers and also on the I5 in the new Colorado and Canyon. I was contracted into the GM plants in Saginaw where this process first went into production.

 

Neat, why couldn't they just make the styrofoam a little bigger LOL. They could have made the heads flow really good and then de-tuned it somewhere else lilke the computer...

 

Well, I don't know about the Styrofoam thing, but I know for prototype heads they use a lost Wax process. They use a Rapid Prototype machine to create a 1:1 model outta wax, make the sand mold, melt the wax out and pour in the molten Aluminum.... How do I know this... There's a shop in town that makes prototype heads for atleast 12 different race teams across the country. Well the raw castings atleast.

There's only 5 aluminum machines like this in the world, 2 in the US, one here in Rochester, and one in Detroit, the other 3 are in Europe, I know BMW has one... I don't know where the other 2 are.

 

Lost wax is also used a lot for custom cast jewelry...
I agree the 'lost foam ' process is widely used these days[a lot better than sand castings of the past]