What are these firewall holes? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**chev-obsession** · 01-25-2024, 02:38 AM

I am in the process of patching unnecessary holes on the cowl and firewall of this cab. I’m curious what the purpose of these holes I’ve circled in red.

Additionally, does anyone know the correct diameter hole for the antenna?

ghackett1 · 01-25-2024, 05:56 AM

Windshield wiper and antenna I think.

**mr.mud1** · 01-25-2024, 08:15 AM

yup,wiper and antenna.the antenna hole over on the rt side,has a big grommet on the antenna cable.

**clay68c10** · 01-25-2024, 09:37 AM

That wiper hole is for RH side drive exports.
The one at the base of the A pillar is for the antenna per the assy manual. I just added that one on my cab this summer.
Not sure about the one inside the cowl. It could be anything.

jumpsoffrock · 01-25-2024, 10:35 AM

2nd pick with two red circles: Left red circle is wiper related; Right red circle is not antenna, because I believe that hole is NOT circled by you, and is located to the left of the left-red-circle....you can see the original antenna hole. I think the right red circle is owner made.

3rd pic with one red circle: not factory, done by owner or rot.

**LockDoc** · 01-25-2024, 12:39 PM

-
From the Factory Assembly Manual.
.

**NGN** · 01-25-2024, 01:14 PM

Just taking a guess but that hole to the right of the wiper arm base also circle red,,, that is set back on to the firewall, is it possibly there for a clip used from the inside cab firewall to hold the padded insulation, sorry for the lack of better words, but something like a round push in clip that goes through the padded insulation through firewall to hold the padded insulation up against the inside cab firewall. It's been a while since I installed mine but I seem to remember it like that. Not a home to check.

**dmb** · 01-25-2024, 02:15 PM

I think we would drill an inch and 1/8 hole for the antenna base, the boss never ordered a plain truck with a radio'
David

**chev-obsession** · 01-26-2024, 01:34 AM

Thank you for all of the responses. Leon, thanks for a clip from the factory assembly manual!

What I’ve learned:

-The antenna hole is home made and not in the factory location.
- The factory installed wiper mounts for right hand drive (export) vehicles.
-The hole on the far right is unknown and likely added by the previous owner for whatever reason.

01-25-2024, 02:38 AM	#1
chev-obsession Registered User Join Date: Jul 2008 Location: kennewick, WA Posts: 1,513	What are these firewall holes? I am in the process of patching unnecessary holes on the cowl and firewall of this cab. I’m curious what the purpose of these holes I’ve circled in red. Additionally, does anyone know the correct diameter hole for the antenna? Attached Images __________________ 1965 c/10 swb 1969 c/10 lwb

01-25-2024, 05:56 AM	#2
ghackett1 68 C10 Longbed Join Date: Sep 2006 Location: Naples, Florida Posts: 519	Re: What are these firewall holes? Windshield wiper and antenna I think.

01-25-2024, 08:15 AM	#3
mr.mud1 Registered User Join Date: Dec 2020 Location: Joggins Nova Scotia Posts: 1,597	Re: What are these firewall holes? yup,wiper and antenna.the antenna hole over on the rt side,has a big grommet on the antenna cable.

01-25-2024, 09:37 AM	#4
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,996	Re: What are these firewall holes? That wiper hole is for RH side drive exports. The one at the base of the A pillar is for the antenna per the assy manual. I just added that one on my cab this summer. Not sure about the one inside the cowl. It could be anything. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ Last edited by clay68c10; 01-25-2024 at 10:52 AM.

01-25-2024, 10:35 AM	#5
jumpsoffrock Registered User Join Date: Apr 2014 Location: California Posts: 978	Re: What are these firewall holes? 2nd pick with two red circles: Left red circle is wiper related; Right red circle is not antenna, because I believe that hole is NOT circled by you, and is located to the left of the left-red-circle....you can see the original antenna hole. I think the right red circle is owner made. 3rd pic with one red circle: not factory, done by owner or rot.

01-25-2024, 12:39 PM	#6
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,846	Re: What are these firewall holes? - From the Factory Assembly Manual. . Attached Images __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

01-25-2024, 01:14 PM	#7
NGN Registered User Join Date: Nov 2001 Location: Old Bridge,NJ Posts: 838	Re: What are these firewall holes? Just taking a guess but that hole to the right of the wiper arm base also circle red,,, that is set back on to the firewall, is it possibly there for a clip used from the inside cab firewall to hold the padded insulation, sorry for the lack of better words, but something like a round push in clip that goes through the padded insulation through firewall to hold the padded insulation up against the inside cab firewall. It's been a while since I installed mine but I seem to remember it like that. Not a home to check.

01-25-2024, 02:15 PM	#8
dmb Active Member Join Date: Sep 2023 Location: randolph va Posts: 165	Re: What are these firewall holes? I think we would drill an inch and 1/8 hole for the antenna base, the boss never ordered a plain truck with a radio' David

01-26-2024, 01:34 AM	#9
chev-obsession Registered User Join Date: Jul 2008 Location: kennewick, WA Posts: 1,513	Re: What are these firewall holes? Thank you for all of the responses. Leon, thanks for a clip from the factory assembly manual! What I’ve learned: -The antenna hole is home made and not in the factory location. - The factory installed wiper mounts for right hand drive (export) vehicles. -The hole on the far right is unknown and likely added by the previous owner for whatever reason. __________________ 1965 c/10 swb 1969 c/10 lwb



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