Hi,

I have a 74 coupe and I need to have the correct vent mechanisms installed for the non a/c cars. The rear deck is from a car that came with air conditioning and they are blocked off from the factory.

Does anyone know the best way to open them up to install the proper factory vent system for the non a/c car. Did GM use two different rear decks when building the cars and the ones that came with a/c just never had the fiberglass cut away, or did all the rear decks come with the holes cut out and then a filler plate used and glued in.

If it is just a filler plate I maybe able to remove them without too much problem.

Any help would be great

 

Maybe I'm missing something, but isn't the rear deck the same for A/C and non-A/C cars? In the case of the A/C car, it does not have the "flapper" mechanism and vacuum servo; it has the vent openings to the interior covered with a plate. The non-A/C car has the "flapper" hardware installed over those openings.

Also, there is a difference in the "flapper" design between the coupe and the convertible, so you will need to find one from a coupe.

I think you just need to remove the block-off cover plate and install the "flapper"...plus run the vacuum line to the actuator.

 

Id suggest leaving it closed. Doesn't do anything for providing air flow IMO.

 

Cars equipped with AC do not have an operational rear vent system.

 

I know this... I need to open the vent holes to install the flapper mechanism as its a non a/c car. The rear deck is from an a/c car so they are currently blocked. As someone stated earlier there may just be a plate blocking the holes and is sealed in there due to several paint jobs etc. After leaving the assembly plant 36 years ago.

 

As I stated earlier, there are gaskets and block-off plates screwed to the vent openings in the interior of the car [under the rear deck in the storage area]. After you find the correct hardware, just remove the block-off plates and attach the flapper hardware plus run the vacuum line to the actuator. I don't know what else there is to say about this.

 

See this thread to see how I restored mine..

http://forums.corvetteforum.com/c3-g...-pictures.html

 

Purchase the '74 assembly instruction manual (AIM). Follow the diagrams for non-AC cars, put your parts list together, and begin the hunt for the parts.

 

74 was a crossover year for the vents. Some cars had the vents cut out a/c or non a/c on the rear deck and some did not.

If the vents on the rear deck have not been cut out I would just leave well enough alone. But it you must cut them out make sure the tray was installed under the deck vents. There is a tray under these vents that the blockoff plate went on or on non a/c car it had the astro vent. flappers installed.

By all means make sure the tray is under the area of the vents if it's not and you cut the holes on top you will have a huge water problem.

Here is a picture of the underside of a rear deck showing the tray I am talking about. Sorry for the small pic.

 

I didn't know that there were C3's made with the holes not cut in the rear deck (outer skin). If that is the case with your car, I would say it's not really worth the effort to reinstall that whole system. But, you could, if that's really what you want to do. It is imperative that the drainage system be completely sealed and capable of diverting any water to the rear wheelwells. Heck, if the deck isn't cut out and the drainage trough isn't there, I doubt that the openings are cut in the wheelwells, either.

 

Yea on the 74 parts car I had the upper vent holes were not cut out but it had the grills in place.
And then I hoped to salvage the a/c block off plates for my 72 and the tray was gone all together. I can't remember about the holes in the fender wells being there or not.
It was a 74 with a/c but I have seen a few other post here about non a/c cars having the grills but no holes cut out on the rear deck so I would guess that the tray was missing from those cars also.

 

First I would like to thank everyone for their help and input on this. Anyway I just got home from work and took a look at my 74 coupe along with my brother who also has a 74 coupe (with A/C) and happened to have his car over my house. My car needs to be correct for a NON A/C car and is getting restored back to factory specs with this. The rear deck vents are not blocked off with a metal plate and the tray is not under the vents inside the storage area. There is just fiberglass that was never cut away with the metal vents over them. BOTH CARS ARE LIKE THIS..... I am no sure if my rear deck is correct for a NON A/C car. The question is did GM just give up on the vents mid year on both A/C and NON A/C cars. My car was built 3/74 and my brothers was 9/74 (both late in the production year). I know the AIM book says "this and that" but it may not be correct here if the car was a late production run. I really dont care if the vents work or not as long as its the way it would have come from GM as a NON A/C car. In fact if its the case that at the end of the year they abandoned these, that would probably be the best and easiest.

After they decided to have the vents not cut out at all I really couldnt see GM having two different whole rear decks sitting there, some with the holes cut and some without depending on a/c or non a/c. Seems like this would have been more work, taken up more space, and would have been more time consuming then just using the block off plates like they did at the start of the production year.

Anyway, can anyone verify a factory 1974 coupe NON A/C with these vents not cut out at all and delivered this way??? It seems very easy to verify one with A/C.... but I needa a NON A/C car this way...


thanks again

 

My 75 convertible with a/c has the rear deck vents, the fiberglass cut out under them, no tray, but diverters glued to the tank side of the tub, and the two vent holes on the interior tube were sealed with metal plates gasketed and rivited closed. Does not have the logo on the side windows.
All original very early 75.