I hope it's something simple and quickly made right.
It's simply money!
The issue is either in the top end or the bottom, and I can either take it in and diagnose the issue and rebuild again; or I can just start over with a different long block. If it is in the bottom end of the motor, I can't rebuild unless I'm willing to sleeve the cylinders if it needs to be bored out. A new head is pretty affordable but again I'm afraid it will be the diagnosis that'll eat the money.
