Thread: 350 to 305 swap running rich

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ok well to make a long story shot this has been driving me up a wall. I got a 94 chevy with tbi i i had a 350 in it but sadly it spun a bearing so i had a 30 over stroked 305 sitting around with 20k miles on it so i decided to swap it i had to change the heads and intake manifold to take my tbi so im running it with 350 heads i changed out the injectors and the chip over to 305 specs and the damn thing is running rich as hell and smokeing away deffinitly fuel not oil or coolant ran compression tests on all systems coolant and block no changes on anything so i know theres no leaks but i still cant find the problem if anyone can help out please let me know thanx

Scan the codes first to give you a base from where to start. Then see if that will give you an idea. Two major things that control fuel as the thing runs are, MAP sensor and O2 sensor. Tps is not as sensitive and since you didn't adjust that during the swap, I wouldn't be concerned. Besides it doesn't make the fuel rich in this condition. A poor ground to the block can make the system go into closed loop which can cause this thing to belch fuel emissions. Check the codes first and see what it says. DId you use actual 305 computer for this? or keep the 350 computer and change chips? The two computers are flashed for each application and will cause the thing the do goofy things by rechipping it alone.

i used the stock computer so the comp is still from the 350 i was told it is ok to use the old comp just needed to change out the chip i had checked the egr that seems to be working fine ill throw it on the computer today and see what happens i know timing is off been haveing problems finding the vac advance wire but i know its close to the mark thanx ill post with what ever codes it shows in a bit

While your there working on it, Double check the little things like Block grounding and proper vacuum source to MAP sensor and little things like that. It could even be a solution of putting the 350 stuff back in the ECM. A good reference point to start if this problem persists.