Ok so i see this has been gone over a ton. I never find the exact info i need. I did as far as injectors went, spacer, no spacer, adapter etc.

Problem i am having is this. I bought the holley rails. I could never get them to stop leaking. LS1 injectors, fast 102, spacers, holley rails. Injectors fit snug, top bottom everything. Im guessing the final angel being snugged down is causing the leak? Im not sure, i couldn't get them to stop, tried 15x

Fast forward, picked up some fast rails now. aaaaaaaand the injectors with stock oring seems like it will NEVER push into the fast rail. The size difference is easily noticeable. No where does it say use a different oring, but that's the only way i see using these even possible? Cant even check if they will bolt up or not due to not being able to get injectors in. The spacing does not look the greatest but i still have hope. Im curious about these orings now. If i have to use ls3 rails for life i guess i will, aftermarket rails just look 1000x better.

Oh, yes i am using the fat bottom orings in the intake.

 

Did an LS swap recently using a china intake/rails and had fuel spraying and vacuum leaks everywhere. Took extra time to tweak the mounts so that the injectors were situated correctly. Our first instinct was to tighten the mounts with the injectors perfectly vertical but they actually are tilted slightly. No problems since.

Do the injectors fit in the fast rails without O-rings on?

 

without orings yes they do. thats why im assuming they need a different size. im just not familiar with sizes of orings and figured instructions would say what size? i realize this is all aftermarket so tweaks are required, but this seems like it should be instruction listed.