Not everything goes according to plan! Here are a few examples of that rule...

Case #1 - Router Mount....

Pic 1
Foamy is all ready with sprues glued on
Pic 2
Melting some AL
Pic 3
Pouring some AL
Pic 4
Motor Mount Foamy Melting... Pouring... Fail!

ConclusionI think what's happened here (and happened many times before for me) is the adhesive I was using to glue the sprues onto the foamy was melting the foamy at the joint causing a hard area that was not allowing the AL to flow and it blew out the side of the sprue and sand...

So the very next thing I tried was to actually cut the sprues when I cut the foamy

Pic 5
New foamy with sprues part of the design!
Pic 6
New Motor Mount Foamy Failed Casting
ConclusionI think on this one I just didn't have enough aluminum and I didn't pour fast enough