DIY Firewall Feed Through

DIY Firewall Feed Through

Postby Lumpy [OP] » December 4th 2011, 8:59pm

I needed some multi conductor cable fed through the firewall for signal lines to some
underhood relays.

Here's what I did -


Found a convenient (yeah right!) spot to drill a 9/16 inch diam hole through the firewall.
This spot was just outboard from the hole that the hood release cable goes through.

Drilled, deburred, filed the hole and edges, then fed through a heavy piece of
rubber hose about 24 inches long. Wet paper towel below the hole to catch metal
filings and anything else that might want to fall into the alternator.

I drilled first with a 3/32" drill to verify the hole on both sides, and to get a pilot hole in place.
Then finished enlarging it with a Uni bit. Takes just seconds to drill with one of those big Uni's.
I use them for everything. Buy the cheap ones at Harbor Freight, 3 sized set for $9.

Hole and hose outlined in yellow.

Image


The OD of the hose is just slightly smaller than the hole.

Image


Here's where it comes through to the inside of the cabin. Outlined in yellow.

Image


Once on the inside, I wrapped a few turns of copper wire around the hose. The copper is
not tight, not cinching the hose. It's pretty loose. I just want to make a "bump" in the hose
that I can fill with RTV.

Image


Here's the cable I fed through it. 6 - 22ga conductors. It's not going to carry any appreciable current.
Just signal wires for relays. Don't need big wires, just several wires.

Image


Covered the copper "bulge" with RTV then pulled the hose from the engine side
so that the RTV covered bulge snugged up against the INSIDE of the firewall.
Then squirted RTV around the OUTSIDE of the feed through.

Difficult to see the outside seal here, lots of wires and hoses in the way.
I've outlined the hose and seal in yellow.

Image


Here it is completed from the engine side. Wires aren't yet in use. It's temporarily
tied up with some zip ties against some other cables and hoses. When I'm ready to
finish the install, I'll simply snip the zip ties and route the cable where I want it.
It's a few feet oversize so I can route it to anywhere I might need a wire from
dash to engine compartment.

Image


Here's the completed dash side. AC register and switch panel is temporarily
removed, gone to the OD green paint booth. The multi conductor cable is
outlined in yellow. It's a few feet "too long" on this side as well so I can
route this side of it to wherever I might want.

Image


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Re: DIY Firewall Feed Through

Postby Jasen » December 4th 2011, 9:45pm

Nice. But what I wanna know is, who do you talk to on all those radios'
I'm a Journeyman woodworker,
Every projects a journey man.

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Ultra gauge

Being a mad scientist IS NOT as easy as it look's on TV



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Re: DIY Firewall Feed Through

Postby RECox286 » December 4th 2011, 9:58pm

I have been putting off drilling a penetration in the firewall so I can replumb the two very small plastic vacuum pipes (which of course are crumbled from age) that go thru the

firewall with the electrical bundle. I think you may have found the only available 1 square inch that would be suitable, Ha. Good show, Gov. My ego is boosted !

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Set a man on fire and he will be warm the rest of his life.

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Re: DIY Firewall Feed Through

Postby Black89cs » December 4th 2011, 11:35pm

Nice. For my amp cable I found a flat spot right by the shifter cable to drill through. It's invisible inside the van and almost easy to miss in the engine bay since it's below the brake booster.
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Re: DIY Firewall Feed Through

Postby Lumpy [OP] » December 5th 2011, 2:21am

Black89cs wrote:
Nice. For my amp cable I found a flat spot right by the shifter cable to drill through. It's invisible inside the van and almost easy to miss in the engine bay since it's below the brake booster.



I already used that space up for cables for those radios.. :rofl:


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Re: DIY Firewall Feed Through

Postby Black89cs » December 5th 2011, 2:30am

hahaha I see. The thing that wasn't fun for me is once I got everything wired up I found out the amp had some serious issues, so now I've got a nice AWG4 cable run to the back with nothing to hook to it, so I've got it disabled for now.
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Re: DIY Firewall Feed Through

Postby 4barrel » December 20th 2011, 5:37pm

Thats using your dipstick!
Yes The hardest part now days is finding a "spot" that can drill both sides. I just bought a small cheapo right angle air drill. this thing is like a mini die grinder. Can't wait to try it out!

The big trick I used to do when intalling stereos and heated seats, Was this. Take a length of soild brake line about 18-24" long, leave the bubble flare on one end & cut the tube on a angle making a little point. /\ Now you can use this tube to puncture stock rubber gromets like near the colum of most vehicles. If you push through from opposite side you are working from. Then slide the wire into & through the tube. Then go and pull the tube back out. this will leave the wire in the rubber.
This works Very well with smaller wires like 12-18ga. Tubes I.D is the biggest wire you can do.

No pics handy but picture it looking like the HOSE with wires in it. The hose being the solid tube. But instead of drilling into metal> it gets "pushed" though existing rubber.
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Re: DIY Firewall Feed Through

Postby Lumpy [OP] » December 21st 2011, 4:36am

4barrel wrote:
... I just bought a small cheapo right angle air drill. this thing is like a mini die grinder. Can't wait to try it out!


I bought one of those $20 right angle air drills at HF. Takes a pretty hefty compressor,
which I don't have. I took it back.

Very clever idea about the sharpened brake line push through the grommet trick... :thumbup:


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Re: DIY Firewall Feed Through

Postby 4barrel » December 21st 2011, 7:02am

Ya I just got my compressor home and wired ( took about 6 months) A Big one :D lol so really itching to to giver a work out, but think my pressure switch has gone piff''. Get it fixed soon enough.

Also I paint my "cheater rod" bright red or next time I have this florecent green. Then you will see it in even low light.
Never had any problems but as always use some discression when poking in there, don't hit any air bag or abs crap!
Had One guy pop a air bag in shop one day when I was younger. He had seat reclined and was upside down-ish under colum/dash think he hit the tube with his super sharp "snap on" test light. BOOM !!!!!He p*ssed himself in the car LOL Don't blame him HAHA I was shaking all day, scared hell outta me.
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