Is it neccessary to use a heating core or baking strips when baking a cake larger than 10 inches? I am doing a 12in round and having trouble finding a store in my area that carries heating cores. Ughh.

No. Use an upside-down flower nail sprayed with a little Pam. Works great!

Moxey's right, the flower nail will work

It only leaves a little bitty hole too, instead of a giant one like the heating core.

Heating cores are just another piece of crap that Wilton thought up to sell you. It has NO value.

WHAT IS THE PURPOSE OF A HEATING CORE? OR UPSIDE DOWN FLOWER NAIL?

The purpose of it is to conduct heat to the middle of the cake. This is especially useful in larger cakes where the sides tend to bake alot faster (since they are against the hot metal of the pan) and the center takes forever to bake.