Smaller fuel injectors

[That00SierraGuy]

Hi all, I tried to search and maybe I'm just not finding it but I'm currently in the middle of swapping my 2000 Sierra 1500 5.3. I am using the 5.3 out of a 1999 Silverado and from what I can find the only difference is cam, injectors, and tune (feel free to correct me if I'm wrong). My question is will I be fine using the smaller 99 injectors with my stock 2000 computer or will it lean out since its tuned for larger injectors?

[Brian715]

I didn't know they were different sizes. I've done 2 swaps now without any ill effects. One a 2000 block into an 06 and one a 01 block into a 99. If it worries you its really easy to pull your injectors and use your exiting ones, unless there is something wrong with them.

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[That00SierraGuy]

I dont know for certain if they are different but that's what I've read, I just figured if check first.  Did you use the original computer and everything from the truck (so different year computer than engine)? Also I believe the injectors are junk and dont want to buy new ones if I dont have too.

[Brian715]

Yes I used the original computer both times. I have just swapped the whole fuel rail when I needed to change them. I have kept all my extra parts and they have come in handy and saved me money when things break.

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[That00SierraGuy]

Yeah I'm keeping everything since the engine that came out still runs and drives it just got a knock, so I have a lot of parts still.

[Brian715]

From what I can tell the 99 had 21lb/hr rated injectors and the 2000 had 25lb/hr injectors. Delphi PN- fj10063 and 62.

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[That00SierraGuy]

Thank you for the part numbers btw.  But yeah I just wasnt sure if running the smaller 99 injectors with stock tune for bigger injectors would cause it to run lean.