Anyone here swap a 4.3 out to a 5.7?

[Russell]

Hey guys!

Has anyone here done a 4.3 -> 5.7 swap? Less the obvious flywheel / clutch stuff, and exhaust, is there anything else that I may be missing?

May be putting a TBI 350 into a 96 GMC 1/2 ton that currently has a TBI 4.3.

Thanks!

Russ

[pcmcobra]

check out www.ls1truck.com
tons of guys have done those swaps. I too am planning a late model efi swap into my tired 86 305.

[vern350]

i'm swaping an 89 350 TBI for my 4.3 in my 88 next month. Frame mounts must be changed and are a hassle from what i found out. Fan shroud is different. Computer must be changed.... can't think of anything else at the moment.

[greg0380]

I swapped my 85 4.3 for a 305, so its basically the same thingas a 350. I needed new engine stands, the V6 ones are a totally different animal. I had to drill one new whole in the frame to mount the V8 stands. It puts the back of the engine in the same spot as the V6 so I didn't have to move the tranny. Fan shroud is different, upper and lower radiator hose as well.

I used the V6 flywheel (two piece rear seal) and clutch. Haven't any vibrations or problems.

I think you know enough about the computer and stuff to know the things your will need there.

[Russell]

Originally Posted by greg0380

I swapped my 85 4.3 for a 305, so its basically the same thingas a 350. I needed new engine stands, the V6 ones are a totally different animal. I had to drill one new whole in the frame to mount the V8 stands. It puts the back of the engine in the same spot as the V6 so I didn't have to move the tranny. Fan shroud is different, upper and lower radiator hose as well.

I used the V6 flywheel (two piece rear seal) and clutch. Haven't any vibrations or problems.

I think you know enough about the computer and stuff to know the things your will need there.

Yeah, the EFI will be the easy part...

Unfortunately, it sounds like swapping a 350 in is a bit more work than I thought if I have to replace the engine crossmember...

I'll probally just leave the V6 in there if I buy the truck.

[gldevall]

I did it in my 86. You don't have to change the crossmember. You just have to change the motor mount towers. Just about everything will change over except for the obvious, intake and exhaust. It is real easy swap. I did it in three days and that was having to wait for the motor mount towers and day of cleaning.

[edman87]

yea, what gldevall said. Motor mounts different, fan shroud different, prom different and thats about it other than motor. easy swap. Why do you have a tbi 4.3 in a 96? Is that a canada thing? Is it factory?

[edman87]

to gldevall: you wouldn't be kin to a monte devall from over there would you?

[Russell]

Originally Posted by edman87

yea, what gldevall said. Motor mounts different, fan shroud different, prom different and thats about it other than motor. easy swap. Why do you have a tbi 4.3 in a 96? Is that a canada thing? Is it factory?

Nah, just uninformed, LOL

Its actually a Vortec 4.3 with an NV3500. I'll be looking for a Vortec 350 to bolt in. I know that the 4.3 and 5.7 share most of their electronics. Just need to change a few key components that should be on the donor engine, and put a prom in to switch it over.

The rest of the stuff should be easy to find, and put in

I've got a neighbour who has a 98 that I think he is about to get rid of, might be able to pick up the Vortec 5.7 from him...

[edman87]

so you are installing a vortec 350 into a vortec 4.3 truck? It is basically the same except the wiring/ computer part- way more involved. What I was asking is how you had a tbi motor in a 96 truck? To go from a 4.3 vortec to a 350 vortec, there is quite a bit of difference in the wiring I do believe, and the computer is totally different unless you can get a dealership to program it. I would actually like to know what the differences are. Doesn't the vortec 4.3 only have 2 oxy sensors? The 350 has 4. Can't just change a prom, whole comp is different. If you could get the entire truck, it shouldn't be too hard though.

[Russell]

Originally Posted by edman87

so you are installing a vortec 350 into a vortec 4.3 truck? It is basically the same except the wiring/ computer part- way more involved. What I was asking is how you had a tbi motor in a 96 truck? To go from a 4.3 vortec to a 350 vortec, there is quite a bit of difference in the wiring I do believe, and the computer is totally different unless you can get a dealership to program it. I would actually like to know what the differences are. Doesn't the vortec 4.3 only have 2 oxy sensors? The 350 has 4. Can't just change a prom, whole comp is different. If you could get the entire truck, it shouldn't be too hard though.

The connectors on the engine should be pretty similar, though I imagine a different PCM, and a fair bit of re-pinning could be required. Truth is, can't be any worse than any of the brand new engines, and people still swap them around all the time

I probally wouldn't do any swapping for quite some time yet, becuase I simply have no time to do so, and the V6 runs just fine, but it is something to research for a while

[edman87]

Good luck with it. It shouldn't be very bad, fairly easy if you have the donor truck sitting there.

[lurch115]

the radiators would be a good idea to swap out as the one for the 350 should be bigger

[Russell]

Well, I wound up picking this 96 up, and to tell the truth, I'm pretty impressed with the lil' V6. Its definitely not a V8, you can tell that when you pull out to pass someone, but it gets you around pretty well, esspecially around town.

I'm gonna leave it be, unless I wind up doing a 5.3 swap someday