What's This Hole For?

[BHTH]

I tried this on the Blazer board with no luck. I can't imagine it is something specific to Blazers so I'll try here, too. I've got a 1978 K5 Blazer with the Cheyenne package (non-AC), there is a hole in the firewall almost directly in line with the transmission dipstick tube. It is a factory hole with a grommet (just to the right of the ground strap). It's to the right of the floor vents inside the cab. What's it for?

[SunSoaked]

I seriously doubt that hole is "factory." With that said, it could be for anything. Are you the sole owner of the vehicle?

[BHTH]

Originally Posted by SunSoaked

I seriously doubt that hole is "factory." With that said, it could be for anything. Are you the sole owner of the vehicle?

Technically I'm the fourth, but really only the second. I can tell what holes were added for CB, PA, horns and lights. The hole in the firewall liner is too nice around the grommet in the cab. It's got to be factory. I thought maybe a manual choke (did any have that?), but the entry seems too low and the routing to anywhere else would be awkward. I was also wondering about the fan wires if the truck had AC.

[Desert_Eagle02]

I have a 1978 GMC pickup, I will check and see if mine has the hole. Mine is non AC though.

[Desert_Eagle02]

I just checked my truck. Mine has the hole in the liner just like yours, but not through the firewall.

[BHTH]

Originally Posted by Desert_Eagle02

I just checked my truck. Mine has the hole in the liner just like yours, but not through the firewall.

Thanks for looking. Do you know if your liner is the original? Just thinking out loud that maybe it was something that was before or after 78. I think this might confirm factory.

[Desert_Eagle02]

Pretty sure it's original, but I don't know for certain as I'm not the original owner. I'm curious as to what it would be used for. Maybe an option on the truck would use it for something?

[BHTH]

Originally Posted by Desert_Eagle02

Pretty sure it's original, but I don't know for certain as I'm not the original owner. I'm curious as to what it would be used for. Maybe an option on the truck would use it for something?

The only other thing I was wondering about was cruise control, but I don't even know if it was around in 78 on the trucks.

[Man With A Gun]

My 77 had Cruise. Non resume GM Cruisemaster.

Any other Pics of the drivers side front 1/4 panel? Looking for any evidence of cruise control equipment.

[BHTH]

Originally Posted by Man With A Gun

My 77 had Cruise. Non resume GM Cruisemaster.

Any other Pics of the drivers side front 1/4 panel? Looking for any evidence of cruise control equipment.

Glovebox sticker doesn't show any cruise option.

[BHTH]

A friend at work is speculating it is for a vacuum line for the AC trucks for the output selector for the dampers. Can anybody confirm this? I remember a vacuum harness that plugged into the selector on my 86, but don't recall a vacuum line down there.

[RotaryRocketeer]

Vacuum operated damper control is definitely a feature of these trucks, but I can't say whether or not it comes through the firewall in that exact spot.

[Dead Parrot]

I looked at my 75 C10 with AC. No hole in liner at that spot. The vacuum line enters the cab just above the bundle of wires at the left edge of your first pic.

Can't see why they would bring the vacuum line below the climate housing as most of the lines for the vacuum pots are ran on the top.

Wild guess: maybe some kind of factory option hole for a CB coax?