1995 454 TBI swap to 1990 350 TBI questions

Aug 2, 2006
59
0
0
NY zip 12538
#1
Yes I know a backwards swap to a smaller engine! This is for a truck that will be used only to plow my driveway. 1995 K3500 single rear pickup with a dead 454. I have removed the 454 and want to install a 1990 350 TBI engine I am pulling from another truck. Since I have the 4L80E trans in the 95 I have to stick with the 95 PCM and wiring, so options are to either make an adapter to put the larger base 454 TBI unit on the 350 manifold or modify the IAC and TPS wiring to allow the 454 harness to hook to the 350 TBI unit.
For those who may have done this does it work better to use the 454 TBI unit on the 350 to keep the PCM programming correct for the injector size, or use the 454 PCM to run the 350 TBI unit?
I think it would be quicker to modify the 454 harness and use the 350 TBI, but I have a couple questions that maybe someone can handle. If I use the 350 TBI unit will the injectors handle the higher fuel pressure of the 1995 pump, or should I switch out the pump to the 1990? Would the higher pressure make the 350 injectors run pig rich? Since the PCM will be expecting the larger injectors I am wondering how it will work driving the smaller 350 units.
Does anyone have schematics for the 1990 and 1995 IAC and TPS sensors so I could modify my harness?
Or does it make more sense to make the 454 TBI fit the 350 engine and do no wiring mods?
Again I am not worried about gas mileage or getting a chip burned, it just has to run well enough to plow snow and not be loading up with fuel.
Thanks for any help!
 

drptop70ss

New member
Aug 2, 2006
59
0
0
NY zip 12538
#2
Re: 1995 454 TBI swap to 1990 350 TBI questions

Wow nobody messes with TBI anymore?
350 is now installed in place of the dead 454, just have to wire up the TPS and IAC wiring to the different style connectors.
 

drptop70ss

New member
Aug 2, 2006
59
0
0
NY zip 12538
#3
Re: 1995 454 TBI swap to 1990 350 TBI questions

Fired the truck up this afternoon, started right up and idled fine. For anyone doing the swap this is 1990 350 TBI with the 350 TBI unit being run by a 1995 454 TBI computer. IAC and TPS connectors are different between the 454 and 350 so the 454 connector ends were cut off and the 350 connectors wired in. Wires are all the same color between the two trucks so I just matched up the colors. I did not run it long since I still have to do exhaust work but there looks to be no issue with the 454 computer running the engine.