280Z-LS3 Posted June 26, 2020 Share Posted June 26, 2020 Tearing down my 1975 280Z car to prep for my build. It's getting an LS3 and will most likely use Holley Terminator Max X wiring harness and ECU. The OEM harness is massive, a ton of wire branching out from the passenger kick panel, see pic. I have read some threads of guys with 240Z using EZ and Painless universal body harnesses with some success while others suggest staying ith the OEM body harness. In either case they will be integrated with what ever engine harness I end up using. My issue with the OEM, although it's in great shape, is it's a ton of wire, connector and brackets located in the general area where I'll need room for a roll cage. I hope to fit a small universal heat/defrost and A/C unit under the dash above the passenger foot well. Looking for some guidance from those that have tackled the 1975 and newer EFI 280Z cars. Does it matter what year, the applied principles being the same? Should I attempt to strip the OEM harness of what I don't need to get it to a manageable size or would it be easier to just get a universal harness? Stripping the harness seems a daunting task while converting over to a universal harness not that much easier if at all... Quote Link to comment Share on other sites More sharing options...
CaliforniaSRZ Posted June 27, 2020 Share Posted June 27, 2020 I have an sr swapped 75 280z. I'm in the process of wiring it right now and I decided to scrap my old wiring because it had already been spliced into multiple times by previous owners. To replace it I have a wiring specialties engine harness and a ez wiring 21 circuit harness. It works well for the most part but you do have to trim a lot of it down because they are intended for carbed cars. My only issue with it is that you must mount the fuse box on the drivers side if you dont want to have to lengthen any of the wires. This means running you're looms through the drivers side as opposed to the factory way of running through the passenger side. Quote Link to comment Share on other sites More sharing options...
grannyknot Posted June 27, 2020 Share Posted June 27, 2020 I kept as much of the original wiring harness as I could, pruned out some of the stock wire and integrated the bmw engine harness into the existing. As long as you have gone through the stock harness and cleaned the contacts and grounds you will be fine, it is a good quality harness. The thing I don't like about new wiring harnesses is they cheap out by using the thinness possible gauge wire they can get away with, that might be great for their bottom line but I would rather have a thicker cooler wire any day. Quote Link to comment Share on other sites More sharing options...
tube80z Posted June 28, 2020 Share Posted June 28, 2020 I think the biggest reason for replacing the harness is its age. All those wires and connections are getting very old and who knows what you have for corrosion and any work hardening of the wire. It's a huge PIA to rewire a street car but you can use the existing harness as a guide and remove/add what you do or don't need and go from there. On modern cars you have a much higher amperage in the charging circuits so all that wiring, fusible links, fuse block need to go. And you're already pitching the engine harness for your Holley ECU so there's little left in the front. You'll most likely replace all the gauges so much of the dash wiring will be changed. And you can see it's not that much of a stretch to just replace it all. In the end you'll probably have a more reliable car and in the event something is wrong you'll know where all the skeletons are buried. If it's any consolation that's my plan on my street car project that I hope to start working on in the next year. Painless seem very proud of their products and I think you can find competitors that are less expensive and feature similar materials and workmanship. Hope this helps, Cary Quote Link to comment Share on other sites More sharing options...
280Z-LS3 Posted June 28, 2020 Author Share Posted June 28, 2020 Good advice everyone and leaning toward replacing body harness. Cary makes a convincing argument with good points on age of wiring, what OEM harness was designed to handle and, most convincingly, what as necessity will need to be replaced as I modify and swap engine, gauges, heating and A/C systems. There is not much left to replace after all that is taken into consideration. Even though my car was well taken care of and unmolested throughout it's life, having been carport or garage kept in San Diego area, the electrical connectors are brittle with corrosion present as Cary mentioned. This is concerning then add the specter of work hardened wire breaking in unknown locations is telling me to ditch the OEM harness. Also, my alt is a 140amp from a 2006 Caddy CTS-V so I will have some amps! Only question now is who makes the best quality harness that can be mounted in the passenger kick panel area? Someone mentioned the EZ and/or Painless are designed for American cars locating the fuse box in the driver's kick panel which makes a few wire runs too short for S30. Maybe an extra long option is available from EZ? Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted June 29, 2020 Share Posted June 29, 2020 (edited) I used an EZ 14 circuit harness mounted on the top of the driveshaft tunnel near the firewall. Mine is strictly a race car (no radio, no Heat/AC, no windshield wipers, etc...). I use a modified ford engine wiring harness between the ECM and engine while the EZ harness supplies all of the other body functions (ignition switch, brake lights, tail lights, gauge illumination, etc..) as well as power to the ECM and fuel pump. I like the compact fuse panel and the 175 amp circuit breaker that come with the kit. It definitely made it easy to clean up the wiring. Edited June 29, 2020 by 74_5.0L_Z Quote Link to comment Share on other sites More sharing options...
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