HelloCustomer I'm Dale and will try to assist you. Discoloration doesn't mean much. Now corrosion is a different story (flaking , gel or green corrosion attached to the cups)
What was the reason you pulled all of the injectors? Do you have an injector cup leaking? If so have you (with all the injectors out) , pressurized the cooling system ( 8-psi) and inspect each cup for leakage?
let me know,
Ok partner, With the engine being hydraulicly locked , It sounds like either you have "PIN HOLES" in the cylinder liners or one or more "INJECTOR CUPs" (like you thought) are cracked or leaking. Now you can have new cups installed without the head being removed. Just takes a trained engine mechanic and some special tools. These guys can be found by asking your local shop who they can refer you to for this process. But you need to be sure they are leaking.
If it is your liners......sorry.....ya got ta remove the head and find out which one is leaking. If you have more than one leaking, I recomend and INFRAME.
hope this helps out,
Lol.....friend I do understand. I will always recommend "INFRAME" opposed to a "CRATE" motor unless you throw a rod or crack the block.
You can get the head checked and while this being done the tech can ck the liners for pin holes in sides of the cylinder liners as well as check the "LINER PROTRUSION". Also you can possibly get help from the shop (if it was a Detroit Dealer) that did the last inframe by what is called " POLICY". The shop manager can /should work with his warranty department and Detroit to help you cover the cost.
Hope this helps,