At this point it is still a heart issue.

I'm trying to track down exactly where in the Bible salvation goes from a heartfelt belief in Jesus to the magic incantation of believe in your heart and say with your lips. 

Now don't get me wrong.  I don't think there is anything at all wrong with vocally stating your belief and allegiance to Jesus.  I don't have a problem with that at all.  It's just that I don't think it is a mandatory part of salvation.  In all four of the Gospels I can't see anywhere that Jesus says that it has to be done that way.  Jesus always describes it as a heart thing.

Well take a look at this. 

Acts 8:34-40(NKJV)

So the eunuch answered Philip and said, “I ask you, of whom does the prophet say this, of himself or of some other man?” 

Then Philip opened his mouth, and beginning at this Scripture, preached Jesus to him. 

Now as they went down the road, they came to some water. And the eunuch said, “See, here is water. What hinders me from being baptized?”

Then Philip said, “If you believe with all your heart, you may.” And he answered and said, “I believe that Jesus Christ is the Son of God.”

So he commanded the chariot to stand still. And both Philip and the eunuch went down into the water, and he baptized him. 

Now when they came up out of the water, the Spirit of the Lord caught Philip away, so that the eunuch saw him no more; and he went on his way rejoicing. 

But Philip was found at Azotus. And passing through, he preached in all the cities till he came to Caesarea.

Here we are in Acts 8 and Philip again makes the point that it is a heart issues; "truly believe".  The eunuch responds that he does believe but I don't see where even here that was an actual condition of his salvation. 

Anyway I'll keep studying this issue.