Opinion: SWB Under Coat

[Fishcop]

John, did you use SKS or Gravitex? I have purchased UPOL's Raptor bed liner for my Land Cruiser project. How would you compare the Gravitex to all the other stuff?

I used UPOL Gravitex (grey for the external areas and black for interior). The Raptor bed liner is 2 part polyurethane product that can be tinted body colour... not the same stuff though, the Gravitex is one part (solvent suspension) and retains some flexibility. It appears to be very similar to the product Porsche used on later 911 bodies, so probably the same composition as the original Wurth.

[edmayo]

My 67S [9/66 German delivery] does have grey PVC under original paint in the interior rear and in the rear wheel wells.

I'm still trying to figure out why your car has that, I've not seen it on my 67 or any earlier cars I've done ???? Another Porsche mystery !!

[66S]

I also have a front fender I took from a 912 66 or 67 that has the same grey PVC. I thought maybe it was a Karmann thing but I just dont know.

[Silverbullit]

The early cars had a layer of Teroson undercoating directly over bare steel. This is why even on unrestored cars there's a layer of rust UNDER the undercoating-- moisture permeates it over the decades and rusts the steel.

I am almost to this very point with 305811S. In your experience, is this rust enough to warrant pan replacement, or is treatable on an otherwise very sound floor? Thanks all for the tips. Brian

[304065]

Brian, the trouble is that the rust is under the undercoat. Hit it with a hammer and it breaks and flakes off. The strong temptation is to leave the undercoat in place-- the trouble is that it breaks off in use and water penetrates it in use. So if you don't take the whole thing down to bare steel, you're just asking for rust to start somewhere.

As to whether it warrants replacing the pan, the classic rust is usually just a light rime of surface rust, but there is no substitute for getting under the car with an icepick or screwdriver and poking it every 1/4" to see if there is weak metal. There probably is.

[ae354803]

I've been looking and haven't been able to find any information about the color of undercoat on a 67 Porsche body 912. It seems later year LWB have grey undercoating. I've seen images from other restorations like Darryl's (http://www.darrylsgarage.com/912/912rust9.htm) that seem to show black undercoat and even some alleged unmolested 67 and earlier that seem to show black undercoat which aligns with what I've seen on my car.

Is there more information about when the change was made from black to grey if there even was a change?

Andy