Hey everyone.
I'm feeling really overwhelmed with all the info out there about the 305 to 350 tbi swap on my 91 firebird. It's mostly the wiring and electrical thats giving me trouble, so I'm hoping someone could answer some questions, or point me in the right direction to posts already written about how to do this.
Do I need to change the ECM under the dash, or is it just the PROM that needs to be changed out and/or reprogrammed somehow?
I'm feeling really overwhelmed with all the info out there about the 305 to 350 tbi swap on my 91 firebird. It's mostly the wiring and electrical thats giving me trouble, so I'm hoping someone could answer some questions, or point me in the right direction to posts already written about how to do this.
Do I need to change the ECM under the dash, or is it just the PROM that needs to be changed out and/or reprogrammed somehow?
Supreme Member
If it had a 305 TBI engine and then you changed the engine to a 350 TBI then all the wires should just plug back in. Then the proper chip for the 350 TBI engine in the ECM.
This is to simple unless I am missing something?
This is to simple unless I am missing something?
As long as the chip is for the same computer (1227746) then you just need the prom.
Junior Member
I had an 89 formula 305 TBI I swapped in a 350 and some decent cast heads from a non-fuelie engine. Kept blowing the MAP sensor. Swapped out the ECM from a chevy caprice 4 door TBI with a 350 and never had the problem again and it ran decent. Only Problem I ever had with it after the ecm swap was it seemed the timing dropped off more at upper RPM's