*HELP* 72 Corvette Vacuum System
Thread Starter
Racer
Joined: Jun 2009
Posts: 316
Likes: 10
From: Beavercreek Oh
*HELP* 72 Corvette Vacuum System
I have a 72 a/c 350 Auto coupe. I am having some issues with routing the vacuum hoses for the headlight/wiper door/heater box. I have several diagrams but none of them indicate where the vacuum hoses are routed and at what location they go through the firewall. I am making progress by looking at photos online but I am just stumped at this point. There are two, aprox 1.5" holes to the pass side of the wiper motor area on the firewall. Please see my photos below. Can anyone tell me what runs through the empty hole? I have the a/c harness running through the one hole that is occupied. I have purchased a 3 hole grommet (Corvette Central part#303043) but this grommet is to small for this hole. Is this the correct grommet for this hole? Is there a metal plate that covers this hole and the grommet is inserted into it which may allow the grommet to fit? Two of my vacuum heater box hoses are two short as well; one of them is the hose with a green line that is laying on the air cleaner. It should run to the fresh air door in the cowl area. I currently have this vacuum hose running through the tach grommet on the drivers side of the firewall. Not sure if that is correct... Please advise
Team Owner
Joined: Sep 2006
Posts: 31,283
Likes: 4,373
From: Westminster Maryland
Hi B,
That firewall hole is on a/c cars only.
It's shown in the A/C section of the AIM. It's on UPC C60, Sheets E1 and E3. The A/C wiring harness passes through that hole in a grommet with a single opening.
The harness is Item #1 on sheet E3, and is shown from the interior side of the firewall.
The harness is also shown from the engine compartment side on sheet E1 but isn't noted as a separate Item.
In your pictures the wiring harness is running through the wrong hole.
The hole where you have the wiring harness is where the vacuum hoses should enter the interior. It's appears to be 3 hole grommet. 1 hole for the vacuum supply to the console a/c controller. 1 hole for the hose that after it passes through the grommet has a T that leads to the controller and the vacuum actuator for recirculating air. 1 hole for the white hose that runs from the console controller to the hot water valve.
I believe the reason your hoses are too short is because of the mix-up as to what firewall hole they run through.
Only the AIM or the Chassis Service Manual will show this level of detail.
Do you have either?
Regards,
Alan
That firewall hole is on a/c cars only.
It's shown in the A/C section of the AIM. It's on UPC C60, Sheets E1 and E3. The A/C wiring harness passes through that hole in a grommet with a single opening.
The harness is Item #1 on sheet E3, and is shown from the interior side of the firewall.
The harness is also shown from the engine compartment side on sheet E1 but isn't noted as a separate Item.
In your pictures the wiring harness is running through the wrong hole.
The hole where you have the wiring harness is where the vacuum hoses should enter the interior. It's appears to be 3 hole grommet. 1 hole for the vacuum supply to the console a/c controller. 1 hole for the hose that after it passes through the grommet has a T that leads to the controller and the vacuum actuator for recirculating air. 1 hole for the white hose that runs from the console controller to the hot water valve.
I believe the reason your hoses are too short is because of the mix-up as to what firewall hole they run through.
Only the AIM or the Chassis Service Manual will show this level of detail.
Do you have either?
Regards,
Alan
Team Owner
Joined: Jun 2000
Posts: 38,923
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From: Southbound
Cruise-In II Veteran
I agree with Alan: the assembly instruction manual (AIM) would be a big help for you. It shows everything you're talking about, including installing the wiper motor and the theft alarm hood switch.
Last edited by Easy Mike; Feb 19, 2014 at 08:55 AM.
Thread Starter
Racer
Joined: Jun 2009
Posts: 316
Likes: 10
From: Beavercreek Oh
Hi Gentleman!
I only have a Corvette 1972 Assembly Manual. Its not the best. Several diagrams of what the hoses go to but none that show how they are routed and the location at which they pass through the firewall. I have looked through it several times and cannot find this information. Where can I obtain this AIM? I was thinking that my issue was that I have the hoses routed incorrectly. My only concern is that the 3 hole grommet that I currently have is too small for the hole in the firewall. I was wondering if there was some sort of plate or adapter that would go in its place and the grommet would snap into the adapter. Are there any pictures out there that would give me an idea of what this is supposed to look like? I usually go to local cruise-ins to verify this sort of stuff but its still a little to cold here in Ohio at the moment.
I only have a Corvette 1972 Assembly Manual. Its not the best. Several diagrams of what the hoses go to but none that show how they are routed and the location at which they pass through the firewall. I have looked through it several times and cannot find this information. Where can I obtain this AIM? I was thinking that my issue was that I have the hoses routed incorrectly. My only concern is that the 3 hole grommet that I currently have is too small for the hole in the firewall. I was wondering if there was some sort of plate or adapter that would go in its place and the grommet would snap into the adapter. Are there any pictures out there that would give me an idea of what this is supposed to look like? I usually go to local cruise-ins to verify this sort of stuff but its still a little to cold here in Ohio at the moment.
Team Owner
Joined: Sep 2006
Posts: 31,283
Likes: 4,373
From: Westminster Maryland
Hi BZ,
The AIM is the Assembly Manual.
I think you'll find the information on the pages I listed which are in the back of the manual in the Option Section.
UPC C60, Sheets E1 and E3.
The grommet you have may be too small because you're trying to put it in the wrong hole in the firewall.
Maybe?
Regards,
Alan
Is this the 3 hole grommet you have? It's the one pretty boy Mike mentions below! It's the one that's ALL the way to the right in your last picture.
The AIM is the Assembly Manual.
I think you'll find the information on the pages I listed which are in the back of the manual in the Option Section.
UPC C60, Sheets E1 and E3.
The grommet you have may be too small because you're trying to put it in the wrong hole in the firewall.
Maybe?
Regards,
Alan
Is this the 3 hole grommet you have? It's the one pretty boy Mike mentions below! It's the one that's ALL the way to the right in your last picture.
Last edited by Alan 71; Feb 19, 2014 at 04:31 PM.
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
At the front of the AIM there is a page showing holes which were drilled through the firewall at the plant. These include holes for the optional automatic transmission and the optional factory AC, including a diagram of how the heat/defrost hole was enlarged for the AC core.
Further in the AIM there is a C60 optional AC section showing the AC installation and the use of the hole in your pic.
I can check these for you in my 72 AIM, but will not be able to do it until later this evening.
If memory serves, all cars got the three hole grommet on the driver's side of the firewall for override vacuum hoses and oil pressure line.
Alan types three minutes faster than I do...but I'm prettier than he is.
Thread Starter
Racer
Joined: Jun 2009
Posts: 316
Likes: 10
From: Beavercreek Oh
Is this the 3 hole grommet you have? It's the one pretty boy Mike mentions below! It's the one that's ALL the way to the right in your last picture.
[/QUOTE]
Yes. That is the correct grommet that I have. I hope it is the correct size. I will pull the a/c harness out tonight and put it in the correct hole and re-evaluate the grommet.
[/QUOTE]Yes. That is the correct grommet that I have. I hope it is the correct size. I will pull the a/c harness out tonight and put it in the correct hole and re-evaluate the grommet.
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Thread Starter
Racer
Joined: Jun 2009
Posts: 316
Likes: 10
From: Beavercreek Oh
I have switched the harness from the drivers side hole to the passenger side hole in the firewall. The grommet that I have is still currently too small. Do I have the incorrect grommet? The outside diameter of my grommet is very close the the hole size in the firewall. Any recommendations in regards to this? I have also attached some pictures here so you can see what the grommet looks like in the hole as well as some photos of where my project is at the moment. I just painted it and have been working on re-assembly
Team Owner
Joined: Sep 2006
Posts: 31,283
Likes: 4,373
From: Westminster Maryland
Hi B,
Car looks NICE!
Dr. Rebuild is usually the best source for grommets.
His catalogue diagrams show a 2 hole grommet for 72 cars (a 3 hole grommet for early 71 cars) but there's no indication that he sells them.
He's not easy to deal with (to say the least) but if you're desperate is it worth a call?
Regards,
Alan
(be sure to put your 'big boy' pants on first!)
Car looks NICE!
Dr. Rebuild is usually the best source for grommets.
His catalogue diagrams show a 2 hole grommet for 72 cars (a 3 hole grommet for early 71 cars) but there's no indication that he sells them.
He's not easy to deal with (to say the least) but if you're desperate is it worth a call?
Regards,
Alan
(be sure to put your 'big boy' pants on first!)
Last edited by Alan 71; Feb 20, 2014 at 10:16 AM.
Platinum Supporting Vendor
Joined: Feb 2004
Posts: 1,771
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From: Sawyer MI
The 3 hole grommet we sell, 303043, will fit into a hole 1 1/8 inch in diameter. The actual hole size is 1 9/16.
Our 302307 grommet would work in this application. Shown below.
Our 302307 grommet would work in this application. Shown below.