L31 motor swap computer question

[RidingDirty98]

if i had a 305 5.0 and i wanted to swap to a 350 5.7 what needs to be done with the computer? would pulling a computer out of a truck that came with a 350 be plug and play?

[redvett01]

Originally Posted by RidingDirty98

if i had a 305 5.0 and i wanted to swap to a 350 5.7 what needs to be done with the computer? would pulling a computer out of a truck that came with a 350 be plug and play?

Yes as long as the donor has the same specs. trans,diff ratio etc. and don't forget if you switch you will have to do a passlock relearn. If you don't have the correct cals in the 350 PCM use the 350 PCM and have it flashed or a custom tune. But by all means use the 350 PCM for your 350ci as the knock module in the PCM is different.

[Randy_W]

I you just want stock 350 performance, it'll run fine on the 305 tuning.

[Pauly]

Just be careful as you are running a supercharger. Running a 350 on a 305 tune wouldnt cause problems naturally aspirated, but with the supercharger any lean issues can cause trouble very quickly.

The Vortec 305 trucks run a smaller single cat exhaust where the Vortec 350 in the 1/2 tons runs a dual cat exhaust with 1 7/9" headpipes that connect the manifolds to the cats. The 3/4 ton and l;arger L31 350 applicatons use a larger 2 1/4-2 3/4" headpipes with even larger cats.

The Vortec 305 uses 3 precat and 1 post cat O2 sensor while the L31 Vortec 350 uses 2 precat and 2 post cat O2 sensors. because of this a Vortec 350 tune may cause issues.

Since you are running a Whipple, I suggest you get an in person tune. the auxillary injectors do provide protection against lean conditions.

peace
Pauly

[redvett01]

Yes running lean and with less timing.

[Randy_W]

Sorry, didn't notice the booster, I would custom tune with a s/c for sure.

[RidingDirty98]

Originally Posted by Pauly

Just be careful as you are running a supercharger. Running a 350 on a 305 tune wouldnt cause problems naturally aspirated, but with the supercharger any lean issues can cause trouble very quickly.

The Vortec 305 trucks run a smaller single cat exhaust where the Vortec 350 in the 1/2 tons runs a dual cat exhaust with 1 7/9" headpipes that connect the manifolds to the cats. The 3/4 ton and l;arger L31 350 applicatons use a larger 2 1/4-2 3/4" headpipes with even larger cats.

The Vortec 305 uses 3 precat and 1 post cat O2 sensor while the L31 Vortec 350 uses 2 precat and 2 post cat O2 sensors. because of this a Vortec 350 tune may cause issues.

Since you are running a Whipple, I suggest you get an in person tune. the auxillary injectors do provide protection against lean conditions.

peace
Pauly

pauly,

so you suggest i stick with the 305 computer and get a custom tune right? i was planning on getting a dyno tune after the swap and gettin full custom 2 1/2 or 3" exhaust piping dual cats and x pipe. would that work alright?.... but how do i fix the o2 sensor placements from the 350 to 305? also what about the 305 and 350 having different knock modules...i didnt know they were different

[RidingDirty98]

also if i remember right i onlt have 2 pre cat sensors and 1 post cat...

[redvett01]

Originally Posted by RidingDirty98

pauly,

so you suggest i stick with the 305 computer and get a custom tune right? i was planning on getting a dyno tune after the swap and gettin full custom 2 1/2 or 3" exhaust piping dual cats and x pipe. would that work alright?.... but how do i fix the o2 sensor placements from the 350 to 305? also what about the 305 and 350 having different knock modules...i didnt know they were different

On e the cover of the modules there are diamond shaped covers with screws just exchange them.

[RidingDirty98]

Originally Posted by redvett01

On e the cover of the modules there are diamond shaped covers with screws just exchange them.

ok thats easy enough but what about this deal with the o2 sensors? is there any way i can fix that problem using the 350 computer? i would also have a problem with the geal ratios being different from the trucks...i have 342's and the donor truck have 373's...and i dont think this matters but the donor truck is a 97 and i have a 98....anyone see any problems with that?