GATOR454

I finally got the Corvette I've been waiting for for nearly 30 years. So I am new to Corvette ownership and this forum. The corvette that I got is a nearly unmolested '74 454 coupe that was in storage for years and only has 67,000 miles on it.

The only thing that appears to be missing is the Astro Ventilation plenum. The underside of the vents were closed off with a painted piece of aluminum.

My question is, Does it work well enough to go through the trouble to track down the pieces and reinstall the system?

I was also thinking of fabricating a custom plenum and attaching a computer base fan that would be run off of a photocell mounted on the back deck to ventilate the interior when it is parked in the sun.

Martin72

Does the car have a/c....if so, the vents are blocked...

bcliff

Does the car have a/c? If so, the plates in the back are original, astro ventilation was not operative with a/c.

GATOR454

Yes, it has A/C. Does that mean it didn't come with one? If so, why did they print Astro Ventilation on the windows?

bcliff

GM probably just had all side windows with the astro ventilation script on them even though A/C cars do not actually have it.

Martin72

You would think that they would have installed the parts on all the cars....and have the vents open on an a/c car when the control was set to vent...but noooo.....only on non a/c cars.

tjl5709

Can they be converted?

Wrencher

There are some vacuum parts and/or cables involved, so it would be a challenge to incorporate on an A/C car. I'm considering some sort of door arrangement that would be operated manually.

I tested the whole idea by removing the two plates and found a couple of problems that may only apply to convertibles. First, you need lots of air volume out of the vents to create enough positive pressure in the cabin to overcome the high pressure area right behind the top. Second, all the seals on the top have to be PERFECT to allow the cabin to pressurize.

Basically on mine, it just sucks in warm air (we're talking hot right now) once I start moving. On a coupe, the area behind the rear glass might be low pressure and it would work better. I used small streamers hanging down over the openings to check airflow in or out.

Hans

trw

Put in a removable rear window and your ventilation problems are gone.

Great mod.

Terry

GATOR454

Thanks for the info.

When I first bought the car I was scrathing my head trying to figure out how it could possibly work and figured it must have been removed. Thanks for enlightening me.

Last night I told my Wife that the car has lied to me twice now. The first is a running battle as to whether or not the door is actually a jar or not (bad switch) and now that it has Astro Ventilation when it never did.

She said "That settles it the car is a Male." I told her that I disagreed and ran away as fast as posible since it would be an argument that I couldn't possibly win. :banghead:

Thanks again
David

marinfarms

how do I find out if my 1974 with A/C have astro ventilation?

Did they not come with it if they had A/C?

marinfarms

I forgot to mention it is a coupe

Thanks for your help

mr303

Astro vents are open when the heater control is in the C position and closed when it is in the H position, they are vacuum operated.

marinfarms

thanks for that. How can I tell if I have the astro ventilation?

Brcmpbl

If you have AC, you don't have Astro Ventilation. It's that simple.

Also, I think this thread is 13 years old.

Haggisbash

If you have an air con car there is no Astro Ventilation other than it says you have on the windows! I have an AC car with most of the AC missing so I took the blanking plate off the vents and leave them open.
I like the computer fan idea to exhaust more air from the cabin but I'm considering using the vent fans they use to get air into race car cabins and put them where the kick panel doors would have been in a non a/c car. Refitting all of missing air con to my car is beyond my budget at least for the time being.

marinfarms

Thank you.
That is exactly what I needed to know. I looked every where on the internet and could not find this info.
Thanks again

Easy Mike

Astro-Ventilation is nothing more than a trade name for GMs fresh air vent system for early C3s. All 68-75s had Astro-Ventilation. AC cars had Astro-Ventilation but used different ducting for cool air handling which non-AC cars did not use. Door glasses have Astro-Ventilation scripts.

marinfarms

Thanks Easy Mike, that helps a lot. I need to replace the driver side window on my 74 with AC. should I get the window with or with out
the Astro-Ventilation. I saw an article that said they installed all
the 74's with windows that had the Astro-Ventilation script on them.

I have to say that this forum has been great for info that is
otherwise hard to find.

Thanks to Everyone

Brcmpbl

Depends what you want, really.

If you want the car to appear as it did from the factory, get the Astro script on the glass. All cars did have the script in 1974, you're correct.

If I was replacing the door glass on my 1970 with AC, I would get the glass with the Astro script, but I like that kind of thing.