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1966 chevelle malibu that im putting a lq4/4l80e into.
Where and what wires are you guys tieing into to integrate the ls harness into the car? Im talking about the ignition feed, battery pos feed, etc.
I tried searching google for a diagram of the bulkhead wiring but for some reason wasnt finding anything.
I have read that some people running the factory dash coolant temp gauge have installed a resistor in line with the wiring crom the sending unit so the gauge doesnt read quite so high in its sweep due to the increased running temp of a ls engine vs a old school sbc. Does anyone know what resistor will put the gauge roughly in the center or so at 200*?
I'm not quite sure I understand your question about the harness. If your asking which wires then I would say none would be tied into an existing wire. Your ignition should go directly to your ignition switch, power directly to your battery and so on. My battery is in the trunk on mine so I got battery power from the starter hot terminal.
As far as the coolant gauge you will more then likely have to mess around with some values until you get it where you would like to see it. I would start with a 100-150 ohm and give it a try. Here's a chart for values vs. temp.
Thank you for the chart. That will give me aomething to reference.
As far as wiring ahat ive done on other swaps is use the existing wiring coming out of the bulkhead fitting on the firewall. Like for example on the 85 jeep cj7 i put the 5.3l into i found what wire out of the bulkhead went to the coil on the factory engine which was a ignition hot wire, i then hooked up my ignition feed on my ls harness to that wire to power up the ls engine stuff. I also figured out what wire going into the bulkhead from the firewall side to the ignition switch was the battery positive feed wire to power the ignition switch and made sure it was connected to batt + on the starter positive terminal.
The wiring was a total mess on the jeep so i had to go about it this way. Main thing im looking for on this chevelle is which wire is ign hot when the key is turned on coming out of the bulkhead connector.
I know what you are talking about and read about it years ago but didn't book mark it. You are looking for what wire stays hot while cranking right? The LS swap is looking for that as an input to the PCM right? but not something that is on the bulkhead side maybe? I remember something like brown and purple at the base of the column but can't be sure.
It's best to tap your ignition wire at the ignition switch or at the back of the original fuseblock before the fuse. This is the only way to have it correctly fused. If you tap into an existing ignition wire at the bulkhead that goes out to the engine bay- that wire is already fused for a certain max load. If you tap all the LS ignition feeds into it then you are seriously overloading that factory circuit. (Can blow fuses or worse- heat up the wires and start a fire).And if you still have the original fuseblock in the car, you are aware that they are not great for adding extra loads. Of course it will work the other way, but you may blow fuses if the load is too high. Many car fires are caused by improper wiring/fusing. Best to do it safely and properly.
Sorry forgot to mention all of my ignition stuff is on a relay and im just going to use the feed from the ignition switch/bulkhead to trigger the relay.
Does anyone have a diagram of the wiring coming out of the bulkhead?
For the ignition source on my 66 GTO I used the original location where the ignition coil wire was, I de-pinned the wire from the bulkhead as it is a cloth covered resistor wire and installed a regular 16 gauge wire there and connected the ignition wire from the stand alone harness to it.
11-17-2015, 09:56 AM
Chevelle swap wiring and gauge questions 
