Would it be detrimental if you failed to perform 64 rounds?
Possibly. Everything else being equal more rounds is better than less. It is a compromise between computing time and security. More rounds won't help however if the algorithm is cryptographically flawed. However if you change anything, you have 'designed' a new hashing algorithm. SHA-256 is deterministic; for a given input there is only one valid SHA-256 hash.
'Rolling your own' cryptography is almost universally a bad idea.
Anyone, from the most clueless amateur to the best cryptographer, can create an algorithm that he himself can't break. It's not even hard. What is hard is creating an algorithm that no one else can break, even after years of analysis. And the only way to prove that is to subject the algorithm to years of analysis by the best cryptographers around.