The cracking community, unlike the bulk of the mainstream programming community, has not lost the art of disassembling executable code. Hiding source code provides negligible additional security.
A breach of your Data should not be a breach of your code.
Always remember: a secure system is secure even if the attacker can see your source code. Any work you do based on assuming the opposite is a waste of time.
At that point, your attacker has not only the ability to derive the salt and attack each password individually, but potentially the ability to generate rainbow tables for subsets of users with identical (or largely identical) derived salts.
The point is that at best, you're adding a term to the overall hardness of the attack. When you use something like bcrypt, you are multiplying the hardness of the attack. There is no comparison between what you've proposed with MD5 or SHA-1 and simply using bcrypt on a random salt, even if the latter has your source code in the latter but not the former.