1jz harness, extend or reroute?

[Arrest_me_red]

So i was getting all set up to extend my harness and just wanted to double check the extension length of 18" and i saw that there was a way to re route the harness to go through an enlarged speedo hole.

Is this true? im surprised i just now found out about this, i've been researching 1jz's for quite a few months now!

If this is a legit mod then can i have a little more detail? thanks!

 

[nctexan]

If I was going to go back and do it over, I would have taken my time and extended my harness to run it through the US harness hole in the firewall. I drilled a hole through the firewall. Allthough much quicker, I now have a hole in my firewall right next to my legs, which is a risk in itself in the event of engine fire, not to mention a path for normal engine heat to dump into the cabin. Plus you have to find a place for the ECU in an already crowded area (mine is squeezed in under my radio), which is not ideal. When I go single I will weld up the hole, and extend the harness. So if I were you I'd just take the time to extend it now, especially if you are already prepared to do so.

 

[lewis15498]

If you are good with wires, extend it, its definitely the better route. If you think you are gonna screw it up, It may be better to have someone else do it or to cut a hole. That said I cringe at cutting holes, and if you do, try to find a gasket or a plug to fill the hole.

 

[Arrest_me_red]

Thank you very much for your input! I will go ahead and extend the harness, 18" correct? now with the body connectors, i should cut the ones off my 7m harness right?

 

[te72]

I can vouch for the ability to put it through an enlarged speedo hole (man that just *sounds* dirty...), HOWEVER... if you ever have to replace your speedometer cable, good luck. That's all I can say. It is NOT fun trying to fish that cable through when your whole harness is stuffed in there too. If I were doing it again (which I will be before too terribly much longer with any luck), I would recommend making an alternate hole. Try to find a gasket/boot that fits the harness and the hole you intend to put in the firewall. Plus you may need something to put in the stock harness hole. Oh, and contrary to popular belief, you CAN put the 1j ecu in the SAME place as the 7m ecu. The trick? Use the 7m's ecu brackets, just swap them over. Easy as pie...

 

[Gt40881j]

Ive done 5-6 swaps and have always just cut a 3" hole right by the throttle cable, run the harness over the a/c behind the climate control, and then the wires will reach to where the stock ecu goes, you just have to flip the ecu around and it plugs right in, you still have to extend the dash harness, but the main engine harness stays intact and ive never had a wiring issue. you have to cut the tape of the stock rubber grommet and slide it down the harness a bit and shove it in the new hole you just made. no heat, water, anything comes through that hole, and you now have a very convenient place to run any other wires and sensors to your engine bay(through the original harness hole)

 

[JonoTurbo]

I've also done a few swaps and I originally ran the harness in a hole cut below the speedo cable area. Even with the grommet on there, the heat came right through. It wasn't very much fun in the summer with no ac and a heat jet on your legs.

However, I did finish up a swap that someone else had started where the harness was routed in a much better way but still not extended. They cut a hole below the heater valve in the part of the firewall that angles outward and ran the harness above the hvac equipment. I was able to mount the ECU in the stock location, facing the correct direction. The body wiring still had to be extended slightly though.

 

[tlo86]

ive always extended it.. the best advice i was given was to use the best wire possible (and i started doing new wire from the plugs themselves to extend it) and i made a connector at the firewall in factory location for easy removal . takes much longer but it works well

 

[hvyman]

I cut the hole. Looks 10x cleaner. I have a rubber part around the harness so nothing hits the wires.
I only used a 2.25 in hole so the plugs and wires barely fit.
No problems with heat or smell.

I'd never run it in the bay again. Less heat to the wires looks better without don't. Have to extend potentially causing head aches down the road if something is half assed.