Problems After 305 To 350 Swap

[profox02]

I Swap My 305 To 350 This Weekend...all Went Well,but Now When I Take Off The Line It Bogs Down And Almost Dies..its A 350 With 305 Heads On It..i've Got Premium Gas In It..is There Really A Differance Between A 305 Knock Sensor And A 350??? Cause We Left The 305 Sensor In Cause I Didnt Know Which One To Put In ..(350 W/305 Heads)..what Else Would Do This ......

[clampjockey]

i recently swapped out a 350 for a rebuilt 305; the engine builder told me if i had any problems getting it to run right after the swap to change the cpu chip before calling him. he said problems were more likely to occur going from a 305 to a 350 (like you did) because they don't allow enough fuel thru. he said it always seems to be just stock chips that act up and that if you buy an aftermarket one it doesn't matter if you get one for a 305 or 350. either should work.

[jhaymes2002]

i swapped from a 4.3 liter to 305, and then from 305 to rebuilt 350. all you have to change is your chip, but if you want all of your power you have to change your throttle body.

[rpreston]

Not neccesary to change entire TBI if going from 305 to 350, just the injectors (along with the CPU chip). The knock sensor in the 350 DOES has a different P/N than the 305. Whether there is any actual difference in them, I don't know.

[profox02]

thx for all the info,..after filling up with super gasoline and regaping sparkplugs and retiming...it runs alot better..thx