Info wanted on V6 to V8 swap please

[RollingTerd]

So I have a 96 K1500 4.3 right. Due to the fact you can't find motor mounts for this particular truck, I was thinking of putting a 5.7 vortec in it. I have searched the forum some and come up empty handed. Certainly this swap has been done before right? I mean not a carbed 350 but vortec version. Any thoughts, guidance, or other wise input would be appreciated. Thanks in advance.

 

[kennythewelder]

There are several post on here about that swap. Here is the mist recent.
https://www.gmt400.com/threads/350-swap-questions.45963/

 

[RollingTerd]

Ok sorry. Guess I missed it.

 

[RollingTerd]

While there is good information in that thread, it's not the direction I'm wanting to go. Don't take this the wrong way, but in my thinking throwing a carburated ANYTHING in a vehicle is pretty straight forward. I'm more interested in going from a 4.3 vortec to a 5.7 vortec. I'm planning on having the complete engine harness and ecu. I guess the first question that comes to mind is will 350 exhaust manifolds bolt to the 4.3 y pipe? I have my doubts but then again I was hoping some one has done this and could shed some light. I'm sure there is more to it then remove and replace.

 

[kennythewelder]

It should. A 4.3 is a 350 - 2 cylinders. Are you going TBI to TBI or Vortec to Vortec. This would be easier than going TBI to Vortec or vise versa. The TBI 350s had a Y pipe exhaust I think. Not sure about the sizes though.

 

[RollingTerd]

Vortex for vortec

 

[skylark]

What tranny do you have? If you have a auto then you have a mild stall converter by reusing your V6 converter. With a stick you need a V8 flywheel because they are balanced differently. Are you opposed to doing an LS swap instead? At a minimum you'll need the V8 frame side engine mountsand radiator shroud. I would upgrade to a 34" radiator and electric fans but that is me. I'm 50% certain that the exhaust is different (I don't recall how the exhaust drops on the the cpfi 4.3. Obviously you'll need a complete vortec 350. I would use a 98+ due to tuning options within the pcm. Honestly I would use an 0411 computer. Theoretically you could add the extra wires and for the injectors and run a V8 computer on your current harness, you may have to extend some of the wiring that runs up to the crankshaft sensor, ac and alternator.

 

[RollingTerd]

I want to do the least amount of modding as possible. The original plan was to replace the 4.3 that slug a rod. But like I mentioned earlier mounts wound that up. This truck is an old farm truck I'm trying to get going for a friend. With that being said I'm not realy interested in mods or performance, just want to get this truck back on the road the quickest way possible.

 

[RollingTerd]

4l60E is the tranny sorry left that out.

 

[ala.frosty]

If you're going to the trouble of swapping in a V8, I'd suggest making it a gen 3 LM7 (drive-by-cable '00 - '02). To go from 4.3 to 5.7, you need to change the computer and wiring harness anyway, so jump up to a cheaper, more modern and more fuel efficient engine in the process. The 4L60E in your truck will work with the 5.3 just fine. There's a whole facebook group dedicated to exactly this swap.