I just replaced the head on my 2004 ecotec due to the damn timing chain breaking the guide bolt!! I took out my old injector cups/sleeves to put in the new head. When I went to put them in they don't seem to fit, considering how much of a pain in the ass they were to take out of the old head. My question is, why? I ordered new ones but I'm afraid that they won't fit. Has anyone had this issue or know how to solve it? I was wondering if I just put in the new ones and then seeded the injectors and tightened the rail on would it be ok? Or do they definitely need to be in tightly?

I know this is a little old post but for others. I ran into the same thing while replacing my 2005 engine. Seems the older heads have a larger bore where these cups go. If you try to just install the smaller cups, you will get irratic idle and rpm's surging when you let off the pedal to slow down. I'm sure there is probably something made for this but in one off the sticky's on this site, it says to just swap them over and it will work....WRONG. I bought some slightly thicker o-rings to go on the cups. Once it was sealed tight, it ran like brand new.