4.3 swap to a 5.7

[diesel-doc]

Just new to this forum and I am wondering if anyone has info regarding a swap from a 4.3 to a 5.7 in a 1996 chevy truck.
Iam going to rebuild a 700r4 and use a 385 new chevy engine from the dealer here in town.
Will the tach and speedo work or what will I have to change .Looking for a complete truck for parts, so I will have a computer (ECM) if needed,I hope this is the way to go any info will be good
thank you

[vncj96]

Summit or jegs will have complete kits for swapping everything, its a very common switch and there are alot of companies that offer full kits for the swap

[bill190]

Basically the electronics for everything in modern vehicles is electrically "integrated" with everything else on the vehicle to "work as a team".

Before doing this, you should fully understand the electrical/electronic portions of everything on the vehicle.

So first of all, you have the larger engine and the parts truck.

The big question is if the parts truck uses this same exact engine? (And you are just getting a new engine.)

And basically you could plop that new engine into the parts truck and everything would work like factory?

I ask because the engine computers and sensors are designed for specific engines, fuel systems, throttle bodies, etc. The specific engine goes along with the electrical sensors, wiring harness, and engine computer.

And is the fuel system, throttle body, exhaust system, etc. the same with both engines? Is the parts truck the same year truck as your truck?

Because fuel systems may be different. Fuel pressure/volume, pressure regulator. As well as electrical controls/sensors for these.

And exhaust can be different so far as oxygen sensors go.

But anyway say you could plop the new engine into the parts truck and it would run like factory....

Then perhaps you could transfer this new engine, its electrical sensors, wiring harness, and engine computer to your vehicle and basically the engine would run.

But THEN you would need to learn how that engine/computer integrates with other things on the vehicle.

Like A/C, large electrical loads - The engine computer will increase idle if the A/C is turned on or if there is a large electrical load like rear window defrost, headlights, etc. Sometimes these are wired to the engine computer. Other times the engine computer monitors voltage and will increase idle to keep the voltage up.

So anyway if the donor vehicle is the same year, then good chance the electrical harnesses would be wired the same and the engine computers would operate in the same manner. But you would need to check to make sure!

If a different year, there would be a good chance they changed something and connectors could be different, computers could be different. Wiring to the computer could be different. Might use the same connectors for a harness but certain wires are switched, etc.

Then the transmission has back and forth connections to the engine computer...
Vehicle speed sensor from the transmission
Solenoids on the transmission controlled by the engine computer
Switches and sensors on the transmission which input information to the engine computer
Transmission fluid pressure sensor which inputs information to the engine computer
Transmission fluid temperature which inputs information to the engine computer

Then the vehicle speed signal provided by the transmission to the engine computer would also be provided by the engine computer to...
Speedometer/odometer
Brakes
Radio (increases factory radio volume with speed of vehicle)
Transfer case module if 4x4
Cruise control

Then there might be an electronic adapter for the VSS between the transmission and the engine computer if automatic transmission with 4x4, but not if manual transmission and 2 wheel drive.

OK, then you want to switch the transmissions...
In some cases if the engine computer detects a problem with a sensor, it will go into "default operating mode" or "limp home mode". And this is *specific* for each year/model! They add stuff/change stuff as the years go by.

For example on my 92, the engine computer sets all the spark plug timing. But if the engine computer detects a serious problem with a sensor related to timing, it will turn on the check engine light and in some cases "turn off" computer controlled engine timing. This is called "bypass mode" and control of the timing is handed over to the base timing on the electronic spark module.

So the question is, if the engine computer did not see the correct inputs from the transmission, would it turn on the check engine light and go into some sort of "limp home mode"?

Then there is likely programming or settings in the engine computer for the specific transmission installed. Can this be changed to the new transmission?

Will the new transmission have the same electrical inputs/outputs to the engine computer?

Will the new transmission need to have the engine computer control it? Will the existing settings in the engine computer work or will this need to be changed?

Now if you plop all this into your truck and there are problems, how would you know what the problem was?

- What I would do is first install the new engine in the parts truck and see if everything works ok.

-Then swap the engine and engine computer to your truck and see if that works ok with the existing transmission.

-Then get a guarantee from where you are buying the new transmission that this can be installed in your truck along with complete instructions on how to install it. This should include dealing with the engine computer electrical connections to the transmission and engine computer transmission related software/settings.

So far as learning how all this stuff works and getting wiring diagrams, you would need a GM Factory Service Manual set for your vehicle. And this would cover the parts truck if it was the same model and year. But if the parts truck was a different year and there were changes, then you would need another Factory Service Manual set for that year.

Here is an example of what all an engine computer does...
(Not your engine computer.)
http://www.nwstp.com/chips/P4_docs/Turbo_P4_Doc.pdf

[2ToNe04]

nice info, bill.

[bill190]

nice info, bill.

Thank you!

[vncj96]

Check this out

http://www.gmtruckclub.com/forum/showthread.php?t=14576

[diesel-doc]

great information ,Thaks again ,
I will be putting a 700 r 4 and anew 385 Chevy stroker crate engine drop in engine in my 2 wheel drive truck.I will not be needind O2 sensors as i will be using headers.I will need the dash gauges to function and this will be the extent of the computer driven portion of the truck .
Thanks again,
Marlon

[2ToNe04]

sounds like a good plan diesel doc, keep us updated.

[5speedsilverado]

just so you know the 385 isn't the 5.7, the 5.7 is a 350

[vncj96]

No, but the 350 bored and stroked is a 383/5, i.e. torque monster!!