Couldn't really find any info searching on here, but I have a firebird with a stock 305 besides a summit 600cfm carb with a spacer that was on the car when I bought it, and I want to put shorty headers with y pipe, no cat, to a muffler and I'm wondering if I'll need to rejet the carb or just retune it, I'm no carb expert so thats why Im asking before I install the exhaust.

 

"Rejet" = retune. Same thing. Or, that is at least, "rejet" is one part of "retune".

Any and every carb will benefit from tuning when any change is made to the engine that affects total air flow through it. Unless of course you get REAL lucky and it's mis-tuned NOW, and the change happens to bring the engine into PERFECT accord with the existing tune. I'll let you do the math on how likely that is, though.

 

Makes sense to me, like I said I dont know much about carbs and would like to be prepared for when I do install the exhaust so I appreciate the response

 

It is very rare for any "universal" carb to be close to perfect in calibration right of the box, so yes it needs to be done. Depending on the car, changing the exhaust usually requires the carb jetting to be changed - but sometimes not.

Maintaining the correct a/f ratio (around 13:1)under full throttle is essential to max power, having the correct ratio cruising (14.7:1) gives best mileage and efficiency.