Car Stereos: power cable through the firewall, self tapping screw, wiring loom

Question
I have a 94 toyota corolla 5 speed manual, and i was wondering where i should run my 1/0 gauge cable through the firewall.

Answer
Hi Calvin,

Unfortunately, I'd need to have that car in front of me to find a good firewall access.  I haven't worked on enough 90's Corollas to remember how they're laid out.

In general, if I'm looking for a way through the firewall, I find out where the factory cables and wiring runs through.  If you can find the main wiring loom between the engine compartment and the cabin, your wire may be able to share the access point.  Another thing you can look for is the hood release cable; you won't be able to fit your wire through that opening, but there may be a flat spot next to it where you can drill.

With 1/0 gauge wire, it's very likely that you'll need to drill a hole in the firewall.  If you find a likely spot, be sure to check both sides for clearance.  Test the area by using a short self-tapping screw to make a hole.  (Using a screw instead of a drill bit reduces the chance that you'll damage something on the other side when the drill bit breaks through).  Then look for the hole on the opposite side of the firewall.  If the location looks clear, you can enlarge the hole using a step bit (Uni-bit).  

If all else fails, you can run the wire underneath the vehicle.  Just be sure to use some sort of protective loom around the wire, and secure it to the under-side of the vehicle using cable clamps or zip ties.  Make sure to avoid any moving parts, and don't skimp on the clamps; you don't want any slack hanging down under the car.

I hope this helps.  Good luck!

Brian