305 to 350 vortec on 98 ecsb

[silverado98]

I am planning on buying a 350 vortec out 99 tahoe for $300 but im not sure yet. I am trying to find out exactly what i need to have swap successful and running good. I hear people say got to have a computer from the 350 vortec to read everything well and it will preform like a 350 should, and also the rear end i have on my truck is 3.42 ratio so also that would be ok as well or do i have to go get the 3.73 rear. Well
so please let me out a little and exactly what i need to do.

 

[df2x4]

You're going to need to either swap to a PCM from a truck with a 350 (and all the other options IDENTICAL to your truck), or get yours tuned by someone like Black Bear Performance. Everything else should be fine.

 

[SKFengineer]

If you use the PCM from the donor truck then confirm the Tahoe had 3.42 gears. If it didn't you'll need to adjust the PCM for the rear diff ratio difference between your truck and the donor PCM.

As far as the need to change away from the 3.42 gears that is sort of a personal choice. What I mean is you have to ask yourself what you want to do with your truck. I have 3.42 gears and it is a great all around gear but if you want to tow a heavy trailer or drag race you may want to consider 3.73's or more. Again you have to think about your end game. ( btw, I'm guessing your not drag racing since your just using the stock 350 but I figured I would note it for others. )

 

[silverado98]

If you use the PCM from the donor truck then confirm the Tahoe had 3.42 gears. If it didn't you'll need to adjust the PCM for the rear diff ratio difference between your truck and the donor PCM.

As far as the need to change away from the 3.42 gears that is sort of a personal choice. What I mean is you have to ask yourself what you want to do with your truck. I have 3.42 gears and it is a great all around gear but if you want to tow a heavy trailer or drag race you may want to consider 3.73's or more. Again you have to think about your end game. ( btw, I'm guessing your not drag racing since your just using the stock 350 but I figured I would note it for others. )

So i csn use mines and just have it tuned the then and also what bout all the sensors and injectors do i have to change them as well. if i send my pcm from my truck to get tuned

 

[df2x4]

Might need different injectors, I'm not sure. Everything else should plug right in.

 

[robert614]

it will all plugin you just need a pcm from a truck with a 350 that has same gear and trans

 

[streetperf]

Might need different injectors, I'm not sure. Everything else should plug right in.

The atomizers are the same for 305/350 on vortec L31's. If $$$$ allow they make a actual injector harness assembly with real injectors to replace the factory atomizers. I believe the assembly can be ordered from amazon, or Rock auto. I believe standard igniton parts is the manufacturer.