Firewall Holes

[Mjminino]

Obviously I see which one is for the steering and i know which one is for the heater, but what are all the other holes used for?

[jonzcustomshop]

ok: red: heater bolts, and lower right as you look at it, heater fan wire grommet.
green: engine harness
orange: choke& accessories
maroon: rear wiring harness
lavender: throttle assembly
violet: clutch rod
light blue: brake and clutch pedal assembly bolt holes
white: main wiring harness
that should cover most: some of the smaller holes are bolt holes, and firewall pad holes, also there are attachment holes to route the wiring...

** I missed 2, is yours a 66? the hole next to the clutch rod hole is for the reverse light wire, and the square hole under the steering column is for the emergency brake cable.

[Mjminino]

It's a 64. This is super helpful, thabk you very much. This is how I acquired the truck lol

[3/4ton Randy]

Yes, that is super helpful. My truck came disassembled and I am just starting the wiring. Thanks!

[KVB]

Ditto on the super helpful. Thanks

[aerotruk63]

Oh your good, Jon!

[racecougar]

I made this up a while back for threads just like this one. This was what each hole was used for on our '65 C10.

[jonzcustomshop]

Originally Posted by racecougar

I made this up a while back for threads just like this one. This was what each hole was used for on our '65 C10.

ha! even better than mine, after looking at this I see where my mistakes were...
we should submit this thread to the faq!

[ray_mcavoy]

Originally Posted by racecougar

I made this up a while back for threads just like this one. This was what each hole was used for on our '65 C10.

Excellent diagram!!

A few things I noticed that are different on some trucks:
(1) I think the hole labeled choke cable was only used with inline-6 engines. Dad's '66 (with a 283) has a firewall insulation retainer filling that hole.
(2) The V8 choke cable goes through the same hole as the oil pressure line (using a multi-hole grommet).
(3) When equipped with a factory tach, the wire leading to the coil also goes out through the same hole as the oil pressure line.


And while we're on the subject of firewall holes, does anyone know the factory location for the 3-speed overdrive lockout cable? Did GM run it through a pre-existing hole (such as along with the speedometer cable) or did this option have it's own hole drilled somewhere else in the firewall?

[frankslagoon]

Originally Posted by ray_mcavoy

Excellent diagram!!

A few things I noticed that are different on some trucks:
(1) I think the hole labeled choke cable was only used with inline-6 engines. Dad's '66 (with a 283) has a firewall insulation retainer filling that hole.
(2) The V8 choke cable goes through the same hole as the oil pressure line (using a multi-hole grommet).
(3) When equipped with a factory tach, the wire leading to the coil also goes out through the same hole as the oil pressure line.


And while we're on the subject of firewall holes, does anyone know the factory location for the 3-speed overdrive lockout cable? Did GM run it through a pre-existing hole (such as along with the speedometer cable) or did this option have it's own hole drilled somewhere else in the firewall?

I ran my O/D cable down the speedo cable hole but maybe someone has a truck that came stock with O/D.

[Mjminino]

[forestb]

has anyone made one of these for a 63?

[Micmac]

You guys never cease to amaze me! I downloaded for future reference.

[LVPhotos]

Bringing this one back. Filling holes and want to know if the blue hole has a grommet as all my stuff runs through it. Relized the two hole grommet is choke and oil or Throttle cable. Yellow is throttle arm and mount hole. Green is rear wire harness. Orange is unused and filled.

[racecougar]

Originally Posted by LVPhotos

Bringing this one back. Filling holes and want to know if the blue hole has a grommet as all my stuff runs through it. Relized the two hole grommet is choke and oil or Throttle cable. Yellow is throttle arm and mount hole. Green is rear wire harness. Orange is unused and filled.

The hole with the blue arrow pointing to it looks to me like it could have been added by a previous owner.

[Mjminino]

That's what I was thinking.

[LVPhotos]

I just filled it. I figured I can make a smaller hole with grommet. Not that many would know I filled a ton of holes anyways. Welding away today.

[frankslagoon]

my 63 doesn't have a "blue hole" either.

[Mjminino]

Rock on then