SBC conversion wiring. What Jeep wiring to keep?

DT5150 · 05-12-2009, 07:54 AM

i'm in the final stages of planning the sbc swap but i have some wiring questions. I've searched and read tons of posts and found some of the info i was looking for, but not all. i know this has been done a million times so there's gotta be some answers out there.. i just can't find em.

here's the drive train..

tbi 350
THM350
Dana 300

i'll be installing a tbi 350 using the stock gm ecm and an aftermarket engine wiring harness from affordable fuel injection. so i've got the motor side of things covered. my question pertains to the stock jeep wiring i need to keep. things like ignition, gauge (dash) lights, 4wd light, e-brake light etc. anything else need to stay?

i bought new mechanical gauges, oil, temp, new "stock looking" tach to work with the 8 cyl. motor, and a new voltage gauge to match them. obviously the stock oil and temp connections wouldn't be utilized since i'm going to mechanical gauges, but i do want to retain the lights for them. so i imagine i'll need to keep all the wiring for them and just use the light wire and cap off the rest?

if anyone has knowledge of which wires these are and their whereabouts in the loom, or where they connect to the back of the fuse panel, that would be most helpful. any info or pics are greatly appreciated.

DT5150 · 05-13-2009, 07:51 AM

bump.......

**BioTex** · 05-13-2009, 08:17 AM

I'm installing a 4.3L V6 into my 1950 Willys currently.
After looking at the cost of an aftermarket wiring harness, I decided to pull one from a junkyard. I found a donor, and starting at the firewall connector, I simply pulled everthing in one harness including the computer and all sensors. Paid $150 for everything.

You can cut off the firewall connector, and remove the protective sleeve from the harness, and with a diagram easily downloaded from the web, you can identify all the connectors.

ECM controlled Components

1. Fuel Injectors
2. Idle Air Control (IAC)
3. Fuel Pump Relay
4. Transmisssion Converter Clutch Connecter (for automatics)
5. Electronic Spark Timing (EST)
6. Remote Ignition Coil
7. Electronic Spark Control Module (ESC)
8. Oil Pressure Switch
9. Exhaust Gas Recirculation Vacuum Solenoid

ECM Sensors

1. Manifold Absolute Pressure (MAP)
2. Oxygen Sensor
3. Throttle Position Sensor
4. Coolant Temperature Sensor
5. Vehicle Speed Sensor
6. Knock Sensor

Keep in mind these are specific to my application, which is off an 89 Blazer.
The wiring harnesses are the same vor V6 or V8, difference being the chip in the computer.

Once I identified all connectors, I removed the extras that went to things like A/C relays and whatever. I was left with a harness with maybe 3 or 4 wires that needed 12V on seperate fuses.

It is terribly intimidating at first, but I have never done it before, and I figured it out after a few hours of study. You replace the wire loom with new, and plug all the connectors in, supply power and that should be it.

There is a ton of info about this on other forums devoted to SBC's

Hope this helps.

DT5150 · 05-13-2009, 09:09 AM

thanks, but i think you misunderstood. i'm looking for which jeep wires to keep, not which chevy wires to add.

**BioTex** · 05-13-2009, 10:06 AM

See what happens when I wake up late and log on before at least 5 cups?

I did grossly misread! Sorry.

You could look at the Firewall connection diagram that John labeled, and see what wires go where. It might be close to yours, enough to get started at least.

DT5150 · 05-13-2009, 11:00 AM

now that's helpful

thanks man!

now go back to bed...

**BioTex** · 05-13-2009, 01:45 PM

I used that diagram extensively when I did my swap. It was a lfesaver. I only found 2 mistakes in it. One is the horn wire was not labeled, and can't remember the other, but it is not critical. Did you already purchase a harness?

DT5150 · 05-13-2009, 02:35 PM

nope, not yet. just about to though..

green_jeep · 07-29-2009, 11:50 PM

That diagram is a good piece of info!!!!! answers a cpl questions i have for my swap too
thanks

LIFTANDTIRES · 10-09-2009, 04:37 PM

Bro You Are A Life Saver!

LIFTANDTIRES · 10-09-2009, 04:45 PM

qUESTION NOT RELATED TO WIRING BUT SBC RELATED. I put in the aftermarket radiator. I have one Heater core hose coming off the block of the motor. the other rant to the old radiator. the aftermarket radiator didnt have the outlet for it.. any Ideas or what did you do?

LIFTANDTIRES · 11-27-2009, 10:07 PM

What Did You Do For The Alternator?

Duble-it · 01-03-2010, 05:08 PM

So as far as the rest of the wires in the engine bay that aren't used after the swap? Do you cut and cap em or spool them up and leave them alone ?

DT5150 · 01-04-2010, 09:30 AM

i yanked out the old engine harness, computer and ecm. about the only thing i left in place was the "chassis" harness.. and that diagram did help immensely.

**Redmanchew** · 01-04-2010, 05:11 PM

i really didn't have a lot of extra wires.... after going through the diagram and determining what each wire was i.e. 12 hot, 12 crank, ground, acc on, oil psi, temp,etc.. i managed to reuse most of them. by reuse i mean new wire, new crimp/solder on the bulkhead fitting but in the same spot.
some of the extras like the tach and a 12v hot wires (orange) for the "under hood light" i sealed up and left in the loom in case i decide to need them in the future.