Where to route wires through firewall to interior?

[Coelacanth]

I've installed an electric boost gauge near the stock MAP sensor on my car and I'm wondering where the best, easiest places are to route the electrical wires through the firewall so I can get at them from the inside under the dash? I could minimize the length of wiring needed if it could go through the passenger side of the firewall, if possible.

I'll also be installing a fuel pressure transducer on the driver's side of the engine, those wires will also need to route through the firewall, ideally on the driver's side.

 

[Boxcars]

I don't know that there is a way fin on the passenger side. All my wiring on these cars were routed through a hole I drilled with a step drill just to the left of the vacuum booster (when looking from the front of the car).

 

[Turbo6inKY]

There's a hole below the heater box on the passenger side. On the interior side, it's near the ECM. You can push the grommet through to the interior side to make room for more wires. You'll have to fish them through from the interior with a coat hanger wire or something, because the hole isn't accessible from the engine bay side.

 

[Coelacanth]

Thanks guys! If I decided to drill my own hole and add a grommet, is there an optimal location to make fishing the wires through easiest to get at, from the inside? Boxcars might've answered that already...

 

[Boxcars]

Somewhere between the booster and the accelerator pedal cable. You'll probably have to use a fish wire of some kind because it's tough to see because the hole will be up high under the dash. You could just straighten out a wire clothes hanger, or something like that. Found this picture, you can see a few wires going into the firewall.

https://ibb.co/cN9y7v

 

[earlbrown]

There's a hole below the heater box on the passenger side. On the interior side, it's near the ECM. You can push the grommet through to the interior side to make room for more wires. You'll have to fish them through from the interior with a coat hanger wire or something, because the hole isn't accessible from the engine bay side.

Just be real careful here since that's where the HVAC vacuum lines run through. If you knock on of them loose on the engine side, you pretty much will have to remove the engine to fix it.

 

[Coelacanth]

Somewhere between the booster and the accelerator pedal cable. You'll probably have to use a fish wire of some kind because it's tough to see because the hole will be up high under the dash. You could just straighten out a wire clothes hanger, or something like that. Found this picture, you can see a few wires going into the firewall.

https://ibb.co/cN9y7v

Thanks everyone...this is great, I'll probably go this route too. When I install the fuel pressure transducer for the pressure gauge, I'll use the same location for those wires, too.