GTO1966

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

Alan 71

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

gbvette62

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.

GTO1966

wow. thanks guys for the indepth answer. I didn't know if the vents were just "for show". Pretty advanced for its time.

Alan 71

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

Don Rickles

And all this time I thought they were for collecting mice?

Mr D.

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.

Alan 71

Hi,
Cars with a/c still had the Astro Ventilation script on each side window.
Regards,
Alan

Scrrem

I'm still learning about my 69 too, thanks for asking this
Rich

74Ken

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.

Alan 71

Hi 74,
If your car is a 74 coupe it originally had the rubber tube drains in the plenums that led to near the top each wheel well.
Regards,
Alan

74Ken

Hmmm, will have to look at reinstalling those. They are not there right now for sure.

Thanks again Alan

ENCSDOUG

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

74Ken

Oi, I can feel a cramped job coming up. not a lot of room back there and I am done pulling my seats out now that everything else is fixed back there.

Alan 71

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

Peterbuilt

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.

Mr D.

Now you had to say that, I think I only have it on the Pass side. Forgot to check last night.

See Three

So the cars that had AC just didn't have the system to open and close the vents?

Alan 71

Hi,
I'm so confused as to what cars had what and when.
Every time I think I understand it I realize I don't.
Regards,
Alan

Alan 71

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.