SuperNova
Lieutenant
- Joined
- Mar 16, 2007
- Messages
- 1,455
Re: Question for Chevy V8 Engine gurus
I did this same conversion on a '93 chevy pickup and we had to replace the EPROM chip and the injectors. The flow rate on the injectors is different and during the first minute of running the ECM uses a open loop base map which is calibrated for the 305-not enough fuel for the 350- once it hits closed loop the O2 sensors do their job and modify the fuel delivery to accomodate the larger displacement engine. Even when you swap in the EPROM chip, it is calibrated for the 350 sized injectors and you will still have the same problem, maybe a bit less, but it will still be there. Even in closed loop the smaller injectors force the fuel trim to add fuel so the engine runs stochiometric(14.7-1) which will give you less room for the ECm to adjust fuel for different atmospheric conditions. Also, at some point the injectors won't flow quite enough fuel (think heavy load or steep grade), the engine will lean knock, you won't hear it, but the knock sensor will--it'll retard the timing and you'll be complaining about poor power and poor fuel mileage. The trans will be up and downshifting to keep the engine in power and wear itself out--so on and so on. We took some time to figure it all out, too. And we talked to the "experts" all of whom were wrong. But who knows, maybe it'll be different for you.
--
Stan
I did this same conversion on a '93 chevy pickup and we had to replace the EPROM chip and the injectors. The flow rate on the injectors is different and during the first minute of running the ECM uses a open loop base map which is calibrated for the 305-not enough fuel for the 350- once it hits closed loop the O2 sensors do their job and modify the fuel delivery to accomodate the larger displacement engine. Even when you swap in the EPROM chip, it is calibrated for the 350 sized injectors and you will still have the same problem, maybe a bit less, but it will still be there. Even in closed loop the smaller injectors force the fuel trim to add fuel so the engine runs stochiometric(14.7-1) which will give you less room for the ECm to adjust fuel for different atmospheric conditions. Also, at some point the injectors won't flow quite enough fuel (think heavy load or steep grade), the engine will lean knock, you won't hear it, but the knock sensor will--it'll retard the timing and you'll be complaining about poor power and poor fuel mileage. The trans will be up and downshifting to keep the engine in power and wear itself out--so on and so on. We took some time to figure it all out, too. And we talked to the "experts" all of whom were wrong. But who knows, maybe it'll be different for you.
--
Stan
