EFI Conversion - Where to place hole in firewall for harness

[Mopsquad]

Hello All!

I'm deep into this EFI conversion on my Barracuda with a 426 Hemi.  I'm investigating location to place the 1.5" hole to route the harness.  In the attached pic, is a spot (yellow tape) that I have considered.  Easy access and it places itself superiolateral to the bellhousing on the engine side.  A decent position to get the harness length to the appropriate sensor locations.  I do plan to install A/C in the future and I know that the outlets are more on the passenger side of the firewall.

Looking for comments and alternative locations that I can get at and drill the 1.5" hole

[GoodysGotaCuda]

I put mine through the passenger side firewall near the kick panel.


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[1 Wild R/T]

I've always mounted things in the area of the parking brake assembly & used the existing hole with the body plug intended for the manual windshield washer foot pump hoses..... 

[Mopsquad]

I did consider the existing hole near the driver inner fender (maybe the washer hole you were talking about).  The issue would be that I would have to extend a considerable amount of wiring to get to the appropriate sensors.

[shawge]

I put my MS3Pro in the passenger kick panel area and routed the wires through the heater core holes which were left empty from a non-AC to AC aftermarket conversion.  The EFI harness follows the OEM engine harness along the firewall and splits at the back of the engine to the injectors, coils, and sensors on either side of the engine.

If I were reluctant to make new holes in the firewall, I would not hesitate to extend the harness.  Otherwise, I do like the idea of the harness coming out near the rear of the engine.

[Katfish]

I ran everything through the existing hole for 4spd cars, only works if you have an auto.
I was able to get my 518 OD and EFI harness through it.

[Mopsquad]

Thanks fellas.  It is a 4 speed car and the harness looks thicker than yours.

I'm going to lay out the harness and see how much I can push though the firewall at the washer hole plug to get close to the sensors.

[1 Wild R/T]

Ok, just something you might be able to use... I've make up quite a few of these through the years....    I start with a 3.5" length of 1.5" angle iron, i drill two hole on each of the flat sides... Two allow it to be sandwiched to the firewall with the parking brake assembly, the other two I weld nuts to the backside of... Those holes are where the flat plate picks up two of it's mounting points....The third one is the front mounting point of the parking brake..... I replace the bolt with a 2" light of threaded rod, three nuts, one to lock down the parking brake, the other two sandwich the plate....  I have one old EFI mounting plate that was 7"x8" then it bent 90 degrees & had a second area 7"x4"

[RUNCHARGER]

I've welded enough holes up that I refuse to drill any new ones. I usually run stuff through body plugs, however you would probably have to lengthen wires.

[EFI5spdtom]

Hi Mopsquad.  I put mine right where your tape is--it worked fine.  my computer is above the glove box

[YellowThumper]

Mopsquad, if you have not already committed. I can show you what I did. If your car is not already an AC car and you will be adding aftermarket AC. You can remove the old heater and motor. This leaves the huge firewall hole. There is a Dodge van (1990 ish) that uses a firewall plug that works almost perfectly to snap over hole. I am adding MS3X and routes all mine that way. Of course I cannot find pics right now. I will look them up over the weekend and post. Worked out real well.
Here is a blurry screenshot of one I posted on another site to give you an idea of it.

[YellowThumper]

As previously noted it is incredibly simple. Firewall hole is round with exception of one quadrant of it. Three of the plugs 4 snaps already fit the existing hole. I used a thin plate of aluminum and made the correct full diameter hole in it. Used the existing firewall screw holes to bolt it to the inside. Did not use any sealer for it. The plug covers everything. This left the heater hose holes i temporarily sealed with silicone. Eventually I will add Vintage Air with their bulkhead that is hidden in the fender well.
Wiring loom will be wrapped in a black split nylon mesh and sealed at connection with shrink tubing.

Mike

[Katfish]

Nice job, any other specifics on the donor?

[YellowThumper]

Nice job, any other specifics on the donor?

Unfortunately no. When is saw and purchased it, I did not know how perfect it was going to be. Dodge van, guessing late 90s to mid 2000s. It is up high and in your face on firewall. Above master cylinder. I frequent the yards so I will try and remember to re-look for better specific info.

[Mopsquad]

Mopsquad, if you have not already committed. I can show you what I did. If your car is not already an AC car and you will be adding aftermarket AC. You can remove the old heater and motor. This leaves the huge firewall hole. There is a Dodge van (1990 ish) that uses a firewall plug that works almost perfectly to snap over hole. I am adding MS3X and routes all mine that way. Of course I cannot find pics right now. I will look them up over the weekend and post. Worked out real well.
Here is a blurry screenshot of one I posted on another site to give you an idea of it.

I haven't committed to the hole yet as it is still 110* here and garage work is challenging in that heat.

I will be adding aftermarket A/C , probably Classic Auto Air's kit.  I never thought of how the heater box integrates (or is removed).  I will take a good look into your suggestion before any other cutting is on the table.