4.3 TBI to 350 TBI swap

[Schurkey]

new mounts from Rock Auto are under $10.

Yeah, but they're garbage. The steel shell is half the thickness for easier stamping of the thin sheet metal. And if they can't get that right, I wouldn't trust the rubber insert, either.

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[FrankieD61]

I dont know if the 4.3 uses the same fuel pressure spring either.


I dont know exactly what you mean by a diner truck but if its not a GMT 400 they may not set the proper location forwards and back to let the tranny line up correctly. Also new mounts from Rock Auto are under $10.

Sorry, that was a typo I meant to say "donor" truck. I have motor mounts from that truck.

 

[FrankieD61]

I think, right now, the computer is my biggest concern. And, honestly, is going to be my biggest challenge..

 

[TagAllen]

The computer is very easy to pull out if you find a truck. Also the wire harness pulls out of the fire wall once unplugged its held in with 2 7mm screws. You can still buy the ecm on Rockauto for around $82 to $122 pluss a core charge since you probably dont have a core. The chip you can purchase on ebay. Getting the wire harness out of the donor truck may or may not be hard depending on if it is bolted to the bellhousing bolts.

 

[PlayingWithTBI]

At minimum, you'll need to install the 5.7L injectors. I think the air passages are the same size, but not absolutely certain.

4.3, 5.0, and 5.7 are all 42mm.

I dont know if the 4.3 uses the same fuel pressure spring either.

It does, all of the SBC injectors are rated at 13 PSI nominal. 7.4L are all 13PSI too except for 94 - 95 which are 30 PSI.

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[FrankieD61]

The computer is very easy to pull out if you find a truck. Also the wire harness pulls out of the fire wall once unplugged its held in with 2 7mm screws. You can still buy the ecm on Rockauto for around $82 to $122 pluss a core charge since you probably dont have a core. The chip you can purchase on ebay. Getting the wire harness out of the donor truck may or may not be hard depending on if it is bolted to the bellhousing bolts.

Will I need to change the harness If I change out the computer? I'd like to just be able to change out the PROM chip and be done. If I have to change the whole computer that is fine. I just hope I can find the correct computer/prom combo. If not, I will send mine out and get a custom tune put on it. Like PlayingWithTBI suggested, I can also tune it myself.

 

[PlayingWithTBI]

Will I need to change the harness If I change out the computer? I'd like to just be able to change out the PROM chip and be done.

Here's a link which has a bunch of ECMs by service # and other info including wiring diagrams. You s/b able to match yours up to a replacement or at least, re-pin some of the wires in the connectors.

www.gearhead-efi.com/Fuel-Injection/forumdisplay.php?20-GM-ECM-Bins-TunerPro-Definition-Files-Wiring-Diagrams-Tuner-Info

 

[FrankieD61]

Here's a link which has a bunch of ECMs by service # and other info including wiring diagrams. You s/b able to match yours up to a replacement or at least, re-pin some of the wires in the connectors.

www.gearhead-efi.com/Fuel-Injection/forumdisplay.php?20-GM-ECM-Bins-TunerPro-Definition-Files-Wiring-Diagrams-Tuner-Info

How many pins will I have to touch? Is that a complex task?

 

[FrankieD61]

Will the 1227747 work for my setup?

As a reminder my setup is a 5.7l, Manuel 5 speed, 3.73 gears.

 

[PlayingWithTBI]

How many pins will I have to touch? Is that a complex task?

IDK, figure out what ECM you have now and look at the wiring diagram for it in the link I posted. Then look at the wiring diagram for the replacement ECM.

Will the 1227747 work for my setup?

As a reminder my setup is a 5.7l, Manuel 5 speed, 3.73 gears.

Yes, you need to look for a 7747 with the corresponding chip (PROM) for your set up. They're also in the link I posted under 1227747