So when I got my 66 Starfire in 1998, the previous owner (or someone) had stuffed the spaces between the trunk skin and trunk lid support with open cell foam.

I always wondered why: looked like cr*p, just kind of low rent, if you know what I mean.

Fast forward 10 years to me sorting out two 10" subwoofers in my 1966 98. I finally get the amps & speakers worked out and the trunk rattles like a son-of-a-gun. Just awful.

So I go to the foam store and get some grey open cell packing foam for like $10.00. Yes. Ten bucks. Okay, maybe plus tax...

Then I cut the 16X16X2" chunk into strips and stuffed the foam up into the spaces between the trunk skin & support structure.

Wow. Sounded like a new car. No rattles. Or at least greatly reduced.

For $10.00. Gotta love that.

Can't wait to put the foam between my door panels & the metal doors and see what that will do.... I bought a roll of 1/8" closed cell foam for $50, will cut to fit soon and see if that helps reduce noise in my old car...

cheers
cf

 

 

That is cool. Be careful about driving your car in the rain or on wet roads though. If the foam is up against the fender skin and gets wet it will hold the water and cause rust like nobody's business. Then again, if it is just a weekend warrior you should be ok.

 

I'm not in that habit just yet, but it's a really good suggestion.

With 2 small kids, I have just enough time to get the project work done at a much slower pace than I used to. I don't usually make enough time to document it all, which I should.

Also agree on the water + foam = rust equation. That's why I put it in the underside of the trunk lid and nowhere else. I've never had a rust problem there. In 25 years. It's a CA car, weekender, sees maybe 3,000 miles a year. Less lately.

An open question in my mind is whether closed cell foam makes a difference in water absorption. I think it will since they use it for camping mattresses. What's clear is that open cell foam is basically a sponge...

cf

 

post up some pics

 

Generally speaking, Closed cell foam is going to be pretty much waterproof and/or air-tight. Its very effective as a contact seal between two surfaces. (ie weather stripping) Depending on the type of foam it can be a decent thermal insulator. Not great for acoustic insulation usually but probably better than nothing. Though it can "squish" most times its physically more stiff than compared to Open cell.

Open Cell foam on the other hand is literally what they make synthetic sponges out of. Its usually very soft. It can readily soak up liquids and allows air to pass through the cell structure. Lots of uses, cushions, padding, impact absorbtion. Also a decent thermal insulator, and better at absorbing acoustics than closed cell.

Some times its tough to tell the difference. A quick simple way to test which variety a piece foam might be, is to try to blow air into the foam with your mouth. If it lets the air pass its open cell foam, if it seals your mouth its closed cell.

Just a few gems of knowledge I've picked up along the way, thought i would share.

 

You can also get open cell foam with a skin .... so the outside doesnt look porous but the interior is.

I designed some foam products many years ago. I have seen poured foam do some crazy things. In the old days its was also very very very dangerous. Sniffers at the molders measured in parts per billion !