Which "engine section" firewall hole for painless?

[techlaf]

Painless instructions show my '75 setup with 3 firewall holes: passenger side hole, driver side hole, and engine section hole. But my '75 has two circular holes at engine section, a bigger hole on the bottom and a smaller hole just above it.

Which hole should the painless wiring section labeled "engine section" go through?

Plus, what's up with these grommets? Their instructions don't jive with what's provided. They provide 5 grommets, but only two are the same and I have no idea which one goes where except the smallest one that appears to only fit in the smaller of my two "engine section" firewall holes.

And do I really have to cut them? Factory ones weren't cut.

 

[DirtDonk]

Sounds like you answered your own question about which hole. If the supplied grommet is more closely fitted to the smaller hole, then I'd have to say that's the one it goes in.
Make a cover for the other one, and away you go.

And yes, aftermarket grommets often have to be cut. The factory supplier is set up in such a way as to practically mold theirs on to the wires when making it. Unless they're actually stretching the soft rubber and slipping the wrapped harness through it, I think the tape would be prone to peeling up as wires were "extruded" through.
The only alternative to cutting is to feed each bundle through the grommet hole. If they're all un-terminated, that shouldn't be too much trouble. If they are though, you'd have to pull some of the connectors off and, towards the end, it would probably be a 1-wire-at-a-time kind of thing, and might still be a bit hard to do.
I guess it depends on how closely they're sized to the harness, but I think that's your only alternative. And if there are any large connectors on that junction, they'd likely have to come off first.

Cutting seems counter-intuitive, but it works. During final installation, orient the cut to the bottom, use a little silicone sealer in the joint, and you should be good.

That's just generic info though, since I haven't installed the Painless kit (yet) myself, so haven't had to go through this. Hopefully someone who has will have an answer. Some of the others don't even like the Centech grommets, and take them off and replace them with old scrounged factory grommets instead. Which also have to be cut, by the way.

In the meantime, back to the top!

Paul

 

[techlaf]

Thanks for the advice. Yes, I think the small hole is the way to go since all the wires from that section will fit in that hole. There are a lot of pre-terminated connections so cutting the grommet and silicone seems like the best way.

I'm planning on installing RJM's EFI harness after I get all the bugs worked out of this new harness. Does the EFI harness also run through the passenger side hole?

 

[DirtDonk]

Nope. It's too big by far. Most of the harness is under the hood of course, but the largest section, along with the main connector for the ECU is usually through the firewall in it's own hold. I think the common practice is to cut an oval hole and use a factory grommet.
Or did your EFI harness come with it's own grommet?

Paul

 

[DirtDonk]

Something else I thought I'd mention in the way of a "think ahead" type of thing.
If you're using a new harness, and an EFI setup, are you upgrading to a newer, higher powered alternator? If so, then your main alternator charging wire in the Painless harness is no longer used. Should be the large Black w/yellow, or just plain Black wire.
In that case, you might even want to pull it from it's engine section and terminate it somewhere either under the dash, or to a terminal block under the hood, for later use in powering some high-power accessories. Things like an air-compressor, or high-zoot stereo come to mind. Bottom line is that it no longer needs to lay out over the engine, or even come to the front of the compartment.
I forget if Painless runs it out the middle grommet, or over on the passenger side like stock (probably), but keep in mind what you might want to do with it before you finalize all your details.

In that vein, the RJM harness includes circuits for the water temp and oil pressure gauges. Those two, along with the harnesses' "KEYED-ON" circuit, are tied into that center hole we're talking about.
The EFI harness gets it's "KEYED-ON" signal from that wire, and it gets it's "START" signal from a small Violet wire over at the relay panel that usually hooks to the starter relay's "S" terminal.

Just some things to keep in mine when you're laying it all out.

Paul

 

[techlaf]

I am putting in a 3G alternator and those are the kind of helpful hints I need. My painless harness install is going a lot slower than I thought it would, but I'll get there. Thanks again.