Cavity Foam? Options

[bkrantz]

I have removed all the rigid foam from inside the rear trunk lid trailing edge rib, in order to repair rust. I would like to replace the foam since it adds rigidity and connects the rib (which hosts the trunk latch mount) to the outer skin. Any recommendations on materials and process?

[bbrock]

I'm still torn about the foam - especially the deep cavity by the tail lights. I can see how it promotes rust after it fails (not unlike undercoat) but worry about leaving those tail section open to fill with mud.

Although this article is written for more modern vehicles in mind, it still might be helpful.

https://www.bodyshopbusiness.com/auto-foam-...-misunderstood/

[horizontally-opposed]

I'm still torn about the foam - especially the deep cavity by the tail lights. I can see how it promotes rust after it fails (not unlike undercoat) but worry about leaving those tail section open to fill with mud.

Although this article is written for more modern vehicles in mind, it still might be helpful.

https://www.bodyshopbusiness.com/auto-foam-...-misunderstood/

Had same thought about cavity filler (rubber and the foam) at the back of the rear fenders, but would rather have some wet muck that dries into fine dust in those corners than put foam covered by rubber (or whatever that stuff was...), which definitely promoted rust in my car.

Suspect there's a fine dust/grit up there now from the few times I've driven my 914 in the rain since we repainted it, and am not worried about it. I'm guessing the Germans were worried about a salty slurry of snow and ice getting in there and staying wet through the winter back when 914s were used as daily cars.

Not sure what to say about the trunk lid cavity foam. Can see the point about rigidity. Wonder if there isn't something better now? Maybe not foam, but some sort of spray-in rubber?

[bbrock]

I'm still torn about the foam - especially the deep cavity by the tail lights. I can see how it promotes rust after it fails (not unlike undercoat) but worry about leaving those tail section open to fill with mud.

Although this article is written for more modern vehicles in mind, it still might be helpful.

https://www.bodyshopbusiness.com/auto-foam-...-misunderstood/

Had same thought about cavity filler (rubber and the foam) at the back of the rear fenders, but would rather have some wet muck that dries into fine dust in those corners than put foam covered by rubber (or whatever that stuff was...), which definitely promoted rust in my car.

Suspect there's a fine dust/grit up there now from the few times I've driven my 914 in the rain since we repainted it, and am not worried about it. I'm guessing the Germans were worried about a salty slurry of snow and ice getting in there and staying wet through the winter back when 914s were used as daily cars.

Not sure what to say about the trunk lid cavity foam. Can see the point about rigidity. Wonder if there isn't something better now? Maybe not foam, but some sort of spray-in rubber?

I have 3 miles of dirt road between my garage and the nearest pavement, so there's that to think about. (IMG:style_emoticons/default/unsure.gif)