Take it to the engine shop... problem solved!! They will hot tank it for minimal charge, and it will come out like new. I have used Kero, generally good at getting most stuff off, but won't leave it sparkly like a trip to the hot tank. Other items which attack the metal are going to leave it in an inferior state, and will likely cause you problems when the motor is running.

Thats my thoughts anyways. Elbow grease should help you out a bit too.