Spell with Overload Converted Mana Cost?

[Nidorino]

If you cast a spell for the overload cost (for example Street Spasm) is that the converted mana cost determined by the overload cost?

[Kenji]

Nope. The converted mana cost is still determined by the mana symbols shown in the upper-right hand corner. Remember, when casting a spell involving an 'X' cost, replace all instances of 'X' with whichever number you chose while that spell is on the stack.

So, let's say you cast Street Spasm for its overload cost, and you declare that X is 4. Even though that requires you to pay a total of 10 mana ("44RR"), the converted mana cost of the spell will be 5, since "XR" in the upper-right hand corner of the card becomes "4R" while it's on the stack.