Holes on Firewall? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Big Blue · 09-06-2014, 04:57 PM

Its been a while since I took the truck apart. I am re-placing the wiring (TRIAL) before I prep it for paint. I have two holes on the firewall and I can not for the life of me remember what came out of those spots. The one picture is near the AC unit , the other is on the left side by the booster. WHAT WENT IN THEM???????????. also I have some wire (connectors) that I do not know where they go to. I'll put them on later and see if anyone can help me. I all ready looked into the Elec. Fourm. Thanks , John

MountainGoat1966 · 09-06-2014, 05:02 PM

I believe the one by the A/C unit is where the wires and vacuum line run through for the heater/ a/c controls.
The hole by the brake booster is for the hood release cable.
Both holes have rubber grommets that seal them.

Big Blue · 09-06-2014, 06:55 PM

Thanks Mountaingoat1966, Next question...........Where does the vacuum canister go?????

John

MountainGoat1966 · 09-06-2014, 07:21 PM

Not sure of the cutoff/change year, but both my 83 and 84 have a small spherical vacuum ball that mounts on the A/C box just above where the heater hose fittings are.
I have seen later years use a large ball, mounted on the firewall near the power brake booster.

400/400 · 09-06-2014, 07:39 PM

From your signature it looks like you have an 87 body. I think the hole on the right by the booster is for the throttle cable. My hood release cable on my 80's trucks comes out closer to the driver fender.
On my 85 & 87 the vac canister is on the firewall between the wiper motor & driver fender.

MountainGoat1966 · 09-06-2014, 07:43 PM

Now you guys are gonna make me go outside in the rain to look at my truck to see where the throttle and hood release cables are ....

Big Blue · 09-06-2014, 08:58 PM

Thanks All, I found the canister that went with the truck. It is a BIG BALL one the was mounted on the firewall near the drivers fender and wiper motor. So Mountaingoat1966 and 400/400 are correct on that one. What I noticed is that only ONE HOSE is coming out of the canister. Can you explain this on where does it go to. Thanks Again for all the help, John

MountainGoat1966 · 09-06-2014, 09:14 PM

If you look at the underside, you should find a good sized fitting for the hose going to engine vacuum, and a tiny fitting for the hose that goes into the cab.
The tiny one likes to hide.

Big Blue · 09-06-2014, 09:23 PM

Thanks, You don't Know how much I appreciate this. I'll look later. We are getting rain now. I wished for it so you can go out side and check on things for me.

400/400 · 09-06-2014, 09:29 PM

I think you have the vac ball upside down. On my trucks there's only one port on the vac ball & its pointed up. The hose runs behind the wiper motor mounts, through the plastic sleeve above the booster, and finally splits into the main heater control line near the distributor.

Although I can't verify if that's factory or if it's been changed by a PO.

MountainGoat1966 · 09-06-2014, 09:29 PM

You are very welcome.
We are happy to help others and share what we know from experience.
I live by the motto: If I do somebody a favor and they ask how they can repay me, I simply tell them that someday they will be in a position to help somebody else when it's needed, pass the favor along, and tell them to do the same thing.
I think most of the guys on the forum are pretty much that way when it comes to helping out our brothers and fellow truck owners.
And you didn't need to wish me any rain, we are having a much wetter than normal summer rainy monsoon season here.
I miss a lot of days working on my trucks due to the mud.

MountainGoat1966 · 09-06-2014, 09:33 PM

Quote:

Originally Posted by 400/400

I think you have the vac ball upside down. On my trucks there's only one port on the vac ball & its pointed up. The hose runs behind the wiper motor mounts, through the plastic sleeve above the booster, and finally splits into the main heater control line near the distributor.

That's new to me, but I don't have any experience with big balls. (NO off color comment intended).
All I have worked with are the small ones that mount on the A/C box and have two fittings.
Thanks for teaching me something new.

J Knight · 09-06-2014, 09:38 PM

That hole on the drivers side is for the throttle cable. The hood release cable goes near the fuse block.

400/400 · 09-06-2014, 09:49 PM

Quote:

Originally Posted by Big Blue

Thanks, You don't Know how much I appreciate this. I'll look later. We are getting rain now. I wished for it so you can go out side and check on things for me.

Your welcome. Happy to help.

Here's a pic of the routing on my '85 for your reference.

Big Blue · 09-06-2014, 10:07 PM

Thanks Again, Pictures are worth a thousand words. I will invert the ball later, I'm in the house now. 400 your truck looks like the color my truck Was, like a chocolate brown. When The time is Right and I'm ready to paint, the color I 'm leaning towards is the 2014 Dodge Copperhead Pearl. I know other mfg have the same color type, but the Copperhead Pearl just stands out brighter for me. Again Thanks for all the help, I sure I will have more questions later about other things as I put this thing together after paint.

John

Big Blue · 09-08-2014, 11:51 PM

I wanted to delete the two pictures and post this one but it will not let me edit the post. So I am going to post this one. The holes that are in question are the ones that have a question mark. Thanks Again, John

Greenlee · 09-09-2014, 12:11 AM

The big one on the passenger side is engine harness / computer.

77dwh · 09-09-2014, 01:44 AM

The next to the throttle cable hole is for the dual tank selector wiring

400/400 · 09-09-2014, 05:07 PM

The one next to the fuse block is where the orange kick-down wire comes out and goes to the transmission on my '85 w/ TH400. I don't have that opening on my '87 w/ 700R4.

400/400 · 09-09-2014, 05:12 PM

Speaking of the color. I repainted mine the factory Indian Bronze metallic. It looks good in the sun. You can see a pick in my intro thread here:

http://67-72chevytrucks.com/vboard/s...d.php?t=642157

I think the orange your talking about would look good too.

bdiamond · 09-09-2014, 07:50 PM

On an 82 the ? one is for the ESC computer wiring. I'd buy that its for the TBI wiring on an 87 cab.

Big Blue · 09-09-2014, 08:56 PM

Thanks Everyone, This does not have a computer in it, going the old fashion way. I guess I can plug up some hole then.

Thanks Again for the responses, John

Greenlee · 09-09-2014, 09:41 PM

I added a TBI harness to an 83' cab and the same size hole was already in the exact same spot on both cabs. So I wouldn't fill in the hole until you look at your wire harness.

Chaplain · 10-09-2014, 04:34 PM

...

09-06-2014, 04:57 PM	#1
Big Blue Registered User Join Date: Feb 2005 Location: Northeast--Bethlehem, Pennslyvania Posts: 642	Holes on Firewall? Its been a while since I took the truck apart. I am re-placing the wiring (TRIAL) before I prep it for paint. I have two holes on the firewall and I can not for the life of me remember what came out of those spots. The one picture is near the AC unit , the other is on the left side by the booster. WHAT WENT IN THEM???????????. also I have some wire (connectors) that I do not know where they go to. I'll put them on later and see if anyone can help me. I all ready looked into the Elec. Fourm. Thanks , John Attached Images __________________ Big Blue ( John ) 79 Chevy Pick up.....My Dailey STILL Working on a frame up: 1987 Truck body on a 78 Blazer frame. Need cab blasted to start project. Got the cab BLASTED, Now Prep and Paint. Started to lay SOME BONDO and primer. Done, Ordering paint. Got paint, Stuff painted,Cab,Fenders, Hood more later. 9/7/2015 Got the clear coat on,now time to take one off. Started to put things back (What a nightmare) like the heating and AC stuff,inside wire harness, outside AC unit and booster, still more. May 2016, still working on the inside. Got duck work in,heating and AC. Radio (stock) in dash with after market in console later, Speaker are hooked up, Steering column is in. Getting ready to drop the cab onto the frame, Working on engine now since I have the room. Well here it is 2018, got the engine in and it runs, now I need to get the exhaust system in so I can adjust the lifters, to loud right now. Got the exhaust on now I am waiting for the break parts to come in. Last edited by Big Blue; 09-08-2014 at 11:44 PM.

09-06-2014, 05:02 PM	#2
MountainGoat1966 Registered User Join Date: Jan 2010 Location: northern arizona Posts: 259	Re: Holes on Firewall? I believe the one by the A/C unit is where the wires and vacuum line run through for the heater/ a/c controls. The hole by the brake booster is for the hood release cable. Both holes have rubber grommets that seal them. __________________ "Off the grid and on the seven day weekend plan" "One person cannot know everything, but between all of us, there isn't much we don't know."

09-06-2014, 06:55 PM	#3
Big Blue Registered User Join Date: Feb 2005 Location: Northeast--Bethlehem, Pennslyvania Posts: 642	Re: Holes on Firewall? Thanks Mountaingoat1966, Next question...........Where does the vacuum canister go????? John __________________ Big Blue ( John ) 79 Chevy Pick up.....My Dailey STILL Working on a frame up: 1987 Truck body on a 78 Blazer frame. Need cab blasted to start project. Got the cab BLASTED, Now Prep and Paint. Started to lay SOME BONDO and primer. Done, Ordering paint. Got paint, Stuff painted,Cab,Fenders, Hood more later. 9/7/2015 Got the clear coat on,now time to take one off. Started to put things back (What a nightmare) like the heating and AC stuff,inside wire harness, outside AC unit and booster, still more. May 2016, still working on the inside. Got duck work in,heating and AC. Radio (stock) in dash with after market in console later, Speaker are hooked up, Steering column is in. Getting ready to drop the cab onto the frame, Working on engine now since I have the room. Well here it is 2018, got the engine in and it runs, now I need to get the exhaust system in so I can adjust the lifters, to loud right now. Got the exhaust on now I am waiting for the break parts to come in.

09-06-2014, 07:21 PM	#4
MountainGoat1966 Registered User Join Date: Jan 2010 Location: northern arizona Posts: 259	Re: Holes on Firewall? Not sure of the cutoff/change year, but both my 83 and 84 have a small spherical vacuum ball that mounts on the A/C box just above where the heater hose fittings are. I have seen later years use a large ball, mounted on the firewall near the power brake booster. __________________ "Off the grid and on the seven day weekend plan" "One person cannot know everything, but between all of us, there isn't much we don't know."

09-06-2014, 07:39 PM	#5
400/400 Registered User Join Date: Sep 2014 Location: Central MN Posts: 288	Re: Holes on Firewall? From your signature it looks like you have an 87 body. I think the hole on the right by the booster is for the throttle cable. My hood release cable on my 80's trucks comes out closer to the driver fender. On my 85 & 87 the vac canister is on the firewall between the wiper motor & driver fender. __________________ -400/400 1979 K25 350/SM465/205/44HD/14FF 1985 K20 400/400/208/10/14 1987 V10 TBI350/700R4/208/10/10 '85 Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=643968

09-06-2014, 07:43 PM	#6
MountainGoat1966 Registered User Join Date: Jan 2010 Location: northern arizona Posts: 259	Re: Holes on Firewall? Now you guys are gonna make me go outside in the rain to look at my truck to see where the throttle and hood release cables are .... __________________ "Off the grid and on the seven day weekend plan" "One person cannot know everything, but between all of us, there isn't much we don't know."

09-06-2014, 08:58 PM	#7
Big Blue Registered User Join Date: Feb 2005 Location: Northeast--Bethlehem, Pennslyvania Posts: 642	Re: Holes on Firewall? Thanks All, I found the canister that went with the truck. It is a BIG BALL one the was mounted on the firewall near the drivers fender and wiper motor. So Mountaingoat1966 and 400/400 are correct on that one. What I noticed is that only ONE HOSE is coming out of the canister. Can you explain this on where does it go to. Thanks Again for all the help, John Attached Images __________________ Big Blue ( John ) 79 Chevy Pick up.....My Dailey STILL Working on a frame up: 1987 Truck body on a 78 Blazer frame. Need cab blasted to start project. Got the cab BLASTED, Now Prep and Paint. Started to lay SOME BONDO and primer. Done, Ordering paint. Got paint, Stuff painted,Cab,Fenders, Hood more later. 9/7/2015 Got the clear coat on,now time to take one off. Started to put things back (What a nightmare) like the heating and AC stuff,inside wire harness, outside AC unit and booster, still more. May 2016, still working on the inside. Got duck work in,heating and AC. Radio (stock) in dash with after market in console later, Speaker are hooked up, Steering column is in. Getting ready to drop the cab onto the frame, Working on engine now since I have the room. Well here it is 2018, got the engine in and it runs, now I need to get the exhaust system in so I can adjust the lifters, to loud right now. Got the exhaust on now I am waiting for the break parts to come in.

09-06-2014, 09:14 PM	#8
MountainGoat1966 Registered User Join Date: Jan 2010 Location: northern arizona Posts: 259	Re: Holes on Firewall? If you look at the underside, you should find a good sized fitting for the hose going to engine vacuum, and a tiny fitting for the hose that goes into the cab. The tiny one likes to hide. __________________ "Off the grid and on the seven day weekend plan" "One person cannot know everything, but between all of us, there isn't much we don't know."

09-06-2014, 09:23 PM	#9
Big Blue Registered User Join Date: Feb 2005 Location: Northeast--Bethlehem, Pennslyvania Posts: 642	Re: Holes on Firewall? Thanks, You don't Know how much I appreciate this. I'll look later. We are getting rain now. I wished for it so you can go out side and check on things for me. __________________ Big Blue ( John ) 79 Chevy Pick up.....My Dailey STILL Working on a frame up: 1987 Truck body on a 78 Blazer frame. Need cab blasted to start project. Got the cab BLASTED, Now Prep and Paint. Started to lay SOME BONDO and primer. Done, Ordering paint. Got paint, Stuff painted,Cab,Fenders, Hood more later. 9/7/2015 Got the clear coat on,now time to take one off. Started to put things back (What a nightmare) like the heating and AC stuff,inside wire harness, outside AC unit and booster, still more. May 2016, still working on the inside. Got duck work in,heating and AC. Radio (stock) in dash with after market in console later, Speaker are hooked up, Steering column is in. Getting ready to drop the cab onto the frame, Working on engine now since I have the room. Well here it is 2018, got the engine in and it runs, now I need to get the exhaust system in so I can adjust the lifters, to loud right now. Got the exhaust on now I am waiting for the break parts to come in.

09-06-2014, 09:29 PM	#10
400/400 Registered User Join Date: Sep 2014 Location: Central MN Posts: 288	Re: Holes on Firewall? I think you have the vac ball upside down. On my trucks there's only one port on the vac ball & its pointed up. The hose runs behind the wiper motor mounts, through the plastic sleeve above the booster, and finally splits into the main heater control line near the distributor. Although I can't verify if that's factory or if it's been changed by a PO. __________________ -400/400 1979 K25 350/SM465/205/44HD/14FF 1985 K20 400/400/208/10/14 1987 V10 TBI350/700R4/208/10/10 '85 Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=643968

09-06-2014, 09:29 PM	#11
MountainGoat1966 Registered User Join Date: Jan 2010 Location: northern arizona Posts: 259	Re: Holes on Firewall? You are very welcome. We are happy to help others and share what we know from experience. I live by the motto: If I do somebody a favor and they ask how they can repay me, I simply tell them that someday they will be in a position to help somebody else when it's needed, pass the favor along, and tell them to do the same thing. I think most of the guys on the forum are pretty much that way when it comes to helping out our brothers and fellow truck owners. And you didn't need to wish me any rain, we are having a much wetter than normal summer rainy monsoon season here. I miss a lot of days working on my trucks due to the mud. __________________ "Off the grid and on the seven day weekend plan" "One person cannot know everything, but between all of us, there isn't much we don't know."

09-06-2014, 09:38 PM	#13
J Knight Registered User Join Date: Jun 2011 Location: Baytown TX Posts: 2,219	Re: Holes on Firewall? That hole on the drivers side is for the throttle cable. The hood release cable goes near the fuse block. __________________ John 82 Chevy Silverado 350ci/TH350

09-06-2014, 10:07 PM	#15
Big Blue Registered User Join Date: Feb 2005 Location: Northeast--Bethlehem, Pennslyvania Posts: 642	Re: Holes on Firewall? Thanks Again, Pictures are worth a thousand words. I will invert the ball later, I'm in the house now. 400 your truck looks like the color my truck Was, like a chocolate brown. When The time is Right and I'm ready to paint, the color I 'm leaning towards is the 2014 Dodge Copperhead Pearl. I know other mfg have the same color type, but the Copperhead Pearl just stands out brighter for me. Again Thanks for all the help, I sure I will have more questions later about other things as I put this thing together after paint. John __________________ Big Blue ( John ) 79 Chevy Pick up.....My Dailey STILL Working on a frame up: 1987 Truck body on a 78 Blazer frame. Need cab blasted to start project. Got the cab BLASTED, Now Prep and Paint. Started to lay SOME BONDO and primer. Done, Ordering paint. Got paint, Stuff painted,Cab,Fenders, Hood more later. 9/7/2015 Got the clear coat on,now time to take one off. Started to put things back (What a nightmare) like the heating and AC stuff,inside wire harness, outside AC unit and booster, still more. May 2016, still working on the inside. Got duck work in,heating and AC. Radio (stock) in dash with after market in console later, Speaker are hooked up, Steering column is in. Getting ready to drop the cab onto the frame, Working on engine now since I have the room. Well here it is 2018, got the engine in and it runs, now I need to get the exhaust system in so I can adjust the lifters, to loud right now. Got the exhaust on now I am waiting for the break parts to come in.

09-08-2014, 11:51 PM	#16
Big Blue Registered User Join Date: Feb 2005 Location: Northeast--Bethlehem, Pennslyvania Posts: 642	Re: Holes on Firewall? I wanted to delete the two pictures and post this one but it will not let me edit the post. So I am going to post this one. The holes that are in question are the ones that have a question mark. Thanks Again, John Attached Images __________________ Big Blue ( John ) 79 Chevy Pick up.....My Dailey STILL Working on a frame up: 1987 Truck body on a 78 Blazer frame. Need cab blasted to start project. Got the cab BLASTED, Now Prep and Paint. Started to lay SOME BONDO and primer. Done, Ordering paint. Got paint, Stuff painted,Cab,Fenders, Hood more later. 9/7/2015 Got the clear coat on,now time to take one off. Started to put things back (What a nightmare) like the heating and AC stuff,inside wire harness, outside AC unit and booster, still more. May 2016, still working on the inside. Got duck work in,heating and AC. Radio (stock) in dash with after market in console later, Speaker are hooked up, Steering column is in. Getting ready to drop the cab onto the frame, Working on engine now since I have the room. Well here it is 2018, got the engine in and it runs, now I need to get the exhaust system in so I can adjust the lifters, to loud right now. Got the exhaust on now I am waiting for the break parts to come in.

09-09-2014, 12:11 AM	#17
Greenlee Registered User Join Date: Jun 2004 Location: El Lago, TX Posts: 1,668	Re: Holes on Firewall? The big one on the passenger side is engine harness / computer.



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09-09-2014, 01:44 AM	#18
77dwh Registered User Join Date: Oct 2012 Location: Casey,Ia Posts: 53	Re: Holes on Firewall? The next to the throttle cable hole is for the dual tank selector wiring

09-09-2014, 05:07 PM	#19
400/400 Registered User Join Date: Sep 2014 Location: Central MN Posts: 288	Re: Holes on Firewall? The one next to the fuse block is where the orange kick-down wire comes out and goes to the transmission on my '85 w/ TH400. I don't have that opening on my '87 w/ 700R4. __________________ -400/400 1979 K25 350/SM465/205/44HD/14FF 1985 K20 400/400/208/10/14 1987 V10 TBI350/700R4/208/10/10 '85 Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=643968

09-09-2014, 05:12 PM	#20
400/400 Registered User Join Date: Sep 2014 Location: Central MN Posts: 288	Re: Holes on Firewall? Speaking of the color. I repainted mine the factory Indian Bronze metallic. It looks good in the sun. You can see a pick in my intro thread here: http://67-72chevytrucks.com/vboard/s...d.php?t=642157 I think the orange your talking about would look good too. __________________ -400/400 1979 K25 350/SM465/205/44HD/14FF 1985 K20 400/400/208/10/14 1987 V10 TBI350/700R4/208/10/10 '85 Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=643968

09-09-2014, 07:50 PM	#21
bdiamond Registered User Join Date: Sep 2007 Location: Wichita Falls, Texas Posts: 459	Re: Holes on Firewall? On an 82 the ? one is for the ESC computer wiring. I'd buy that its for the TBI wiring on an 87 cab.

09-09-2014, 08:56 PM	#22
Big Blue Registered User Join Date: Feb 2005 Location: Northeast--Bethlehem, Pennslyvania Posts: 642	Re: Holes on Firewall? Thanks Everyone, This does not have a computer in it, going the old fashion way. I guess I can plug up some hole then. Thanks Again for the responses, John __________________ Big Blue ( John ) 79 Chevy Pick up.....My Dailey STILL Working on a frame up: 1987 Truck body on a 78 Blazer frame. Need cab blasted to start project. Got the cab BLASTED, Now Prep and Paint. Started to lay SOME BONDO and primer. Done, Ordering paint. Got paint, Stuff painted,Cab,Fenders, Hood more later. 9/7/2015 Got the clear coat on,now time to take one off. Started to put things back (What a nightmare) like the heating and AC stuff,inside wire harness, outside AC unit and booster, still more. May 2016, still working on the inside. Got duck work in,heating and AC. Radio (stock) in dash with after market in console later, Speaker are hooked up, Steering column is in. Getting ready to drop the cab onto the frame, Working on engine now since I have the room. Well here it is 2018, got the engine in and it runs, now I need to get the exhaust system in so I can adjust the lifters, to loud right now. Got the exhaust on now I am waiting for the break parts to come in.

09-09-2014, 09:41 PM	#23
Greenlee Registered User Join Date: Jun 2004 Location: El Lago, TX Posts: 1,668	Re: Holes on Firewall? I added a TBI harness to an 83' cab and the same size hole was already in the exact same spot on both cabs. So I wouldn't fill in the hole until you look at your wire harness.

10-09-2014, 04:34 PM	#24
Chaplain Registered User Join Date: Oct 2014 Location: TN Posts: 294	Re: Holes on Firewall? ...

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