What are the vents for???
Thread Starter
Intermediate
Joined: Mar 2017
Posts: 38
Likes: 1
What are the vents for???
The two vents about a foot forward of the gas tank filler door, are they functional or just for show? ...I would assume they have drains underneath so washing and water would not be a problem? ..Thanks guys
Team Owner
Joined: Sep 2006
Posts: 31,315
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From: Westminster Maryland
Hi gto,
Depending on the year of the car and whether it's a coupe or convertible, it will have drains.
The vents in the rear deck are the outlets for the Astro Ventilation System.
All cars have them, but they were part of a function system on cars without a/c.
The vents were opened and closed by using the Hot/Cold wheel on the heater defroster controller.
Regards,
Alan
Depending on the year of the car and whether it's a coupe or convertible, it will have drains.
The vents in the rear deck are the outlets for the Astro Ventilation System.
All cars have them, but they were part of a function system on cars without a/c.
The vents were opened and closed by using the Hot/Cold wheel on the heater defroster controller.
Regards,
Alan
Last edited by Alan 71; Mar 28, 2017 at 08:11 AM.
Race Director
Joined: Oct 2000
Posts: 12,698
Likes: 3,153
From: Shamong, NJ
They're part of the Astro-Ventilation system used on cars without air conditioning.
Astro-Ventilation was a flow through ventilation system GM was using on Corvettes, and other GM cars in the late 60's and early 70's. It used the blower to draw air in through the cowl vents, circulate it through the interior, and vent it through the grills in the rear deck. Cars with Astro-Ventilation have flappers in the rear storage compartment, that control the flow of air through the deck grills.
It was meant to replace vent windows, which GM began eliminating from their cars in 68. GM dropped the grills and the system, in 76.
On cars with AC, they're block off.
Astro-Ventilation was a flow through ventilation system GM was using on Corvettes, and other GM cars in the late 60's and early 70's. It used the blower to draw air in through the cowl vents, circulate it through the interior, and vent it through the grills in the rear deck. Cars with Astro-Ventilation have flappers in the rear storage compartment, that control the flow of air through the deck grills.
It was meant to replace vent windows, which GM began eliminating from their cars in 68. GM dropped the grills and the system, in 76.
On cars with AC, they're block off.
Team Owner
Joined: Sep 2006
Posts: 31,315
Likes: 4,417
From: Westminster Maryland
Hi gto,
It WAS a pretty nifty idea at the time!
The problem was that it was a 'passive' system…. there was no fan to pull fresh air into the car, and no fan to push the air out of the car at the vents.
How much air was moved through the car depended on the speed of the car.
The system and it's ducting was completely separate from the heater defroster system of the car which of course did have a fan.
Regards,
Alan
It WAS a pretty nifty idea at the time!
The problem was that it was a 'passive' system…. there was no fan to pull fresh air into the car, and no fan to push the air out of the car at the vents.
How much air was moved through the car depended on the speed of the car.
The system and it's ducting was completely separate from the heater defroster system of the car which of course did have a fan.
Regards,
Alan
Last edited by Alan 71; Mar 28, 2017 at 08:45 AM.
Team Owner
Joined: Mar 2002
Posts: 44,698
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From: Huntsville AL
Interesting, I just picked up a original 71 factory AC project car and I think the Pass side window says Astro-Ventilation on it. I will recheck that tonight.
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Burning Brakes
Joined: Apr 2012
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From: Bowmanville Ontario
My A/C car has them blocked off and there is no drain. Not sure if a PO removed the drains but it's a pain when you wash the car. I have to use a leaf blower to get the water out.
Racer
Joined: Aug 2013
Posts: 339
Likes: 54
From: Fayetteville NC
74Ken, It's not that difficult to replace the rubber tubes that leads out to your rear wheel wells. The hardest part is drilling out the 3 rivets on each side. I replaced the rivets with small 1/4-20 screws with locking nuts in case I have to replace the tubes again. 
http://www.zip-corvette.com/68-76-co...rain-tube.html
http://www.zip-corvette.com/68-76-cp...n-shields.html
http://www.zip-corvette.com/68-76-co...rain-tube.html
http://www.zip-corvette.com/68-76-cp...n-shields.html
Team Owner
Joined: Sep 2006
Posts: 31,315
Likes: 4,417
From: Westminster Maryland
Hi Ken,
As E D posted it's a bit of a challenge.
But, the main part of the work is done in the wheel well not in the interior.
Once the rubber tube is installed it's just a clamp that needs to be tightened to attach it to the plenum.
You won't know what's needed until you take a look. Something is blocking the plenum drain holes currently or the water in the plenums would be running into your rear compartment.
Regards,
Alan
As E D posted it's a bit of a challenge.
But, the main part of the work is done in the wheel well not in the interior.
Once the rubber tube is installed it's just a clamp that needs to be tightened to attach it to the plenum.
You won't know what's needed until you take a look. Something is blocking the plenum drain holes currently or the water in the plenums would be running into your rear compartment.
Regards,
Alan
Last edited by Alan 71; Mar 29, 2017 at 02:50 PM.
Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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Skip that task!
Hi Ken,
My 74 coupe, born May 1st, came with A/C and the rear vents are blocked off.
Here's a photo from the outside.
Here's from the inside.
The grilles are held in the molded part of the body with four screws.
Pete.
My 74 coupe, born May 1st, came with A/C and the rear vents are blocked off.
Here's a photo from the outside.
Here's from the inside.
The grilles are held in the molded part of the body with four screws.
Pete.
Team Owner
Joined: Mar 2002
Posts: 44,698
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From: Huntsville AL
Team Owner
Joined: Sep 2006
Posts: 31,315
Likes: 4,417
From: Westminster Maryland
Hi ST,
Only cars without a/c had the vacuum operated 'flapper doors'.
I've always thought that cars with a/c had the plenums, but used the block-off plate as shown here. Note the crayon a/c.
Regards,
Alan
Photo from Rick D.
Only cars without a/c had the vacuum operated 'flapper doors'.
I've always thought that cars with a/c had the plenums, but used the block-off plate as shown here. Note the crayon a/c.
Regards,
Alan
Photo from Rick D.
Last edited by Alan 71; Mar 29, 2017 at 03:16 PM.