"Engine Swap"... Vortec 4.3L V6 to Vortec 5.7L V8

severedchris

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I have seen this write up for the TBI 95 and previous models on other forums, but not for the Vortec (96-98 truck) (99 in SUV Models). I want this thread to be a sharing grounds (if you will) for people who have done this swap to share information. Please If you have done this swap post up any knowledge or findings that you have here, so that the information is readily available to people wanting to do this swap.
 

severedchris

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I am almost finished with my swap and these are my findings so far:

1. You will need a set of V8 motor mounts...save your ones from the V6 they are worth some$$$$$
You can re-use your old nuts and bolts, the holes for the V8 mounts are already pre drilled from factory in the frame just further foward.

2. You will need a radiator from a V8 truck...they are larger and include the engine and tranny oil coolers
You will need rubber insulators and brackets from a V8 truck in order to mount the larger V8 radiator in the V6 model pickup or SUV
If you can get the Transmission cooler lines from the V8 truck I would get those as well the V6 lines will work but are bent for the smaller radiator
the proper ones would make for a cleaner install.

3. All of your front running gear I.E. Alternator, A/C Compressor and Brackets will work on the V8.

4. You will need the throttle cable and Cruise Control Module and Cable from the V8 model
The V6 cables will work but will not clamp back onto the factory brackets b/c they are shorter, the cables from the V8 make for a cleaner install.

5. The starter for both the V6 and V8 models are the same.

6. You will need the Engine Bay Wiring harness and the ECU from a V8 truck that is the same year model as your V6 truck.
Others will work but Once again the correct harness will make things simple...If anyone has any wiring diagrams for the Vortec models please post them.

7. You will need the fuel lines from the V8 truck the V6 lines are too short...it is best to replace the two O-Rings at the junction on the back of
the motor if you undo the lines there.

8. You will need the Gauge Cluster from a V8 truck otherwise your RPM reading will not be correct as the V6 Gauge Cluster is Calibrated differently.
Your V6 cluster will work but your RPM reading will be slighltly incorrect.

This is all of the info that I have hunted down and gathered while doing my swap......If you have done this and have additional information or
you have any knowledge on differences between models/submodels please add your info here so that this will be readily available for people
doing this swap in the future as well as pics from your Vortec V6 to V8 Swaps!!!...I will be posting pics asap.





7.
 

RPMGraphics

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i have the diagrams for the c100 connector that goes into the firewall

98 diagrams
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96 diagrams
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you should also check out www.lt1swap.com
 

MOBS

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I'll look into the fabrication needed for the "4.3 to 4.3" swap....I know it requires placing the V6 injectors into the plenum of the 4.3 V8(L99). It's not the easiest engine to find, but they're VERY high revving and fun little engines.
 

severedchris

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thanks Ray!!!!...if anyone has info keep it comin!!!!....Also I have a problem I put a 96 model v8 in my truck (which is a 97) all of my guages read exept my rpm gauge I used the computer and wiring harness from the 96...anyone have an answer for this????


Also in order to get my oil pressure gauge and voltage gauges to work I had to cut the plug off of the harness that came in on the passenger side of my 97 and splice it onto the 96 harness.....plugs were the same but the 97 was a female and the 96 is a male...the inside plug on my truck is also male.
 
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RPMGraphics

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you need to check your old harness & see if it matches the 98 diagram or the 96. easiest way to tell is look at the E8 wire, if it's white 98, black it's 96.
i've been told 96 & 97 are the same & i've been told 97-98 are the same. i'm thinking 97 & 98 are the same.
 

b_faulk75

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Nice to see this thread, i am getting ready to swap a 98 5.7 into my 97 4.3 manual trans truck. I have already rebuilt the engine, just need a cam to finish it up, then bolt the heads on. Still need headers and a clutch kit. Then should be pretty much set, i purchased the whole truck with the v8 in it and took everything i thought i would need, but didnt get the wiring harness or fuel lines, i was thinking all i would need for the harness was to add the wires for the extra injectors. also didnt think the fuel lines were different. Oh well, will post some pics of the swap as it happens. By the way, first post!!!
 
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