How do you run wires through the firewall?

 

It depends on what I can find that already exists and it's location. The factory used a lot of large grommets, and sometimes you can find room in them, or they are so large, you can take them out and cut another access hole beside whatever it's being used for.

If none will do, I will take and cut a decent sized hole to match the od of the rubber vacuum hose I am using, and then run the wires through vacuum hose to protect them in the sheetmetal.

 

I got a great tool off the Mac tool Truck it is a punch with a hole down the center to run the wires thru. I think I saw the same tool on the Snap on truck last month

 

I use a unibit to drill hole then use a push in grommet so the wires dont touch metal . Then when im done with the wiring i seal the grommet with silicone...Lew