Chevrolet 5.7 motor overheating problems

I have a big problem with a Chevrolet 5.7 V8 engine. It is from a vehicle that arrived at the workshop turned off suffered very strong overheating was of such magnitude that the cameras left and melted the pythons a bit. The competent rectifications were made and Lor Arme with new pistons and rings but with the difference that the cameras that are Chevrolet 5.0 where I proceeded to cubate the camera admission and escape from 5.0 are smaller than those of 5.7 .. the engine lights but in less than 5 minutes it reaches 100 degrees and the escape driving is too heated ... what do you tell me =??