305 to 4.3
03-06-2009, 09:52 AM
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305 to 4.3
First off i know why would u put a v6 in where a v8 was...answer it was free. now my question we have done the swap everything is hooked up and will idle fine but as soon as it goes in gear it lobes and wants to stall ,it doesn't stall but wants to ,kinda bogs but there is no black smoke from the exhaust no error codes either. This is the funny thing and probblay is the problem but the original motor was a 1990 305 and the new v6 is a 95 vortec with a tbi we havent sitched the ecm yet but the guy at the parts store said that the ecm came with v6's in that year so we'ed thought we'ed try it. i guess my question is do i have to get the computer from the 95 4.3
03-06-2009, 09:53 AM
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Re: 305 to 4.3
First off i know why would u put a v6 in where a v8 was...answer it was free. now my question we have done the swap everything is hooked up and will idle fine but as soon as it goes in gear it lobes and wants to stall ,it doesn't stall but wants to ,kinda bogs but there is no black smoke from the exhaust no error codes either. This is the funny thing and probblay is the problem but the original motor was a 1990 305 and the new v6 is a 95 vortec with a tbi we havent sitched the ecm yet but the guy at the parts store said that the ecm came with v6's in that year so we'ed thought we'ed try it. i guess my question is do i have to get the computer from the 95 4.3
ps. an ecm comparrison would be nice but can't find one on the net
03-06-2009, 11:17 AM
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Car: 82 Berlinetta/57 Bel Air
Engine: LS1/LQ4
Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Welcome aboard thirdgen.org.
I'm a little surprised it runs at all.
The TBI system is speed density or MAP. It is extremely dependent upon programming assumptions such as engine displacement. You need the ECM tuned to the 4.3, either by reprogramming your current ECM, or getting a 4.3 ECM. However, I have no clue about compatibility between a 3rd gen and the 4.3 ECM - perhaps the TBI forum would be of more help than the Engine Swap forum.
So, I'll move this there.
I'm a little surprised it runs at all.
The TBI system is speed density or MAP. It is extremely dependent upon programming assumptions such as engine displacement. You need the ECM tuned to the 4.3, either by reprogramming your current ECM, or getting a 4.3 ECM. However, I have no clue about compatibility between a 3rd gen and the 4.3 ECM - perhaps the TBI forum would be of more help than the Engine Swap forum.
So, I'll move this there.
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