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Ventilation holes

I just noticed that the slots above my rear window are open with nothing behind them. Isn't there supposed to be some foam behind them? When I was sitting in my car, it sounded like I was outside. I could here very clearly from the rear of the car. That is how I discovered the open slots.
Old 06-23-2010, 08:37 PM
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yup - foam
Old 06-23-2010, 08:50 PM
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There is a foam there but on most of our cars it has deteriorated/crumbled over the years.
No need to worry, water very rarely gets in there.

If you ever need to replace the headliner, that's when you want to put in new foam.
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Old 06-23-2010, 08:51 PM
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Thanks guys, that's what I thought. Is it possible to get back there through the zipper for the sunroof? Also,I just noticed that I typed here instead of hear. Don't want people thinking I'm some uneducated moron. I am an educated moron.
Old 06-23-2010, 09:29 PM
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The zipper is for accessing the back up mechanism for opening and closing your sun roof (in case the electric mechanism fails)

I don't think you'll have enough room to replace the foam from there, but I could be wrong.


(you can edit previous posts to remove typos... I do it all the time )
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Last edited by Geronimo '74; 06-25-2010 at 11:59 PM..
Old 06-23-2010, 09:46 PM
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I don't recall anyone trying via the zipper, but try a search - there are prev. threads on this & somebody might have posted what they did.

The other question is what type of foam to use - maybe it is open cell foam...
Old 06-23-2010, 10:34 PM
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There have been previous threads on this topic, and the foam - as I understood it - serves two functions. One is to keep water out, and the other is noise attenuation. Therefore, the type of foam is important. I would like to replace my missing foam, too, and don't know what the proper original foam was. I don't recall an acceptable foam being mentioned in older threads, but maybe I missed it. I'm mostly interested in reducing noise.
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Old 06-24-2010, 08:02 AM
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best thing to do would be to look up the p/n in the PET

then either get that... OR see if some more modern material has better function than the stock foam
Old 06-24-2010, 11:07 AM
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I agree with open cell foam. Air is supposed to be extracted through the slots via the holes in the headliner.
Old 06-24-2010, 11:43 AM
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agree open cell also - but which one...
Old 06-24-2010, 12:22 PM
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I'll take a high-res pic of the foam. It's a gray open-cell foam with holes about the size of a pinhole. I think figuring out the access and dimensions of that space pose the biggest challenge. An upholstery shop should be able to get the foam for you.
Old 06-24-2010, 12:38 PM
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Is this the same foam rubber you are talking about that is glued to the inside of the roof as sound deadener? Or something else. I don't remember any foam covering the holes when I did the headliner on my 71, many years ago.

Does someone have a picture of how it is supposed to look?

Are non sunroof cars different?

When did they stop using the perforated headliners?
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Old 06-24-2010, 01:45 PM
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Here are pics of the foam.

I've changed my opinion on the foam. I now think this is much ado about nothing. The foam is probably not needed at all. It's just acts as a baffle. It won't attenuate much noise either.

The noise attenuation occurs inside the roof, where there is more foam, backed with cardboard. If you don't have a roof full of foam glued to cardboard, this is why you hear noise.

The outside foam is only about an inch wide, by about a quarter inch thick, running the width of the roof vent cavity. There is a sheet metal backstop. The air is extracted via a horizontal vent that is above this backstop. Therefore outward airflow is pulled out and down through the vent slots. The foam was probably installed by pushing it through one of the vents, and then hooking it and pulling it through the cavity and then pushing it into place.



Old 06-25-2010, 10:01 AM
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thanks for those pics rusnack!

Trackrash - did your '71 have foam glued to the roof?
Old 06-25-2010, 11:15 AM
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Quote:
Trackrash - did your '71 have foam glued to the roof?
Yes, BUT, some one had DELETED the sun roof on my car before I owned it. So I have no idea what it should have had.
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Old 06-25-2010, 07:28 PM
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That looks like the cheap "air filter" foam that they used to use on velocity stacks and other cheap speed equipment. It doesn't do much filtering of air for an engine compared to any reasonable standard but obviously it is great for this.
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Old 06-25-2010, 07:43 PM
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thinking more about this, some sound attenuating ear plugs are made of foam (denser than in the above pic tho), so I expect there is indeed some noise reduction.

how many dB and at what frequency... who knows
Old 06-25-2010, 08:27 PM
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I suspect the foam is there to prevent bugs from walking on in. Also, if you are driving with the windows slightly cracked open, there might be a vacuum at the rear area of the roof, which would suck stuff into the roof vents.

The safety ear plugs are similar to the ones that they sell at the racetracks. It's a closed cell foam similar to neoprene.

Last edited by rusnak; 06-25-2010 at 08:49 PM..
Old 06-25-2010, 08:47 PM
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