filling frame rails with plastic foam

[70 Charger RT]

I seen on Mega Factories recently that Dodge sprays a foam on the inside of the frame rails on their new production Challengers.  I think they do this for noise reduction in part.  I currently have my Charger trunk frame open as I was contemplating spraying (filling) the inside of the frame rail with a spray plastic foam.  Has anyone done this?  Can you forsee any problems as a result?  What type of spray foam should I use if I decide to go ahead with it?  Looking for your advice.

[twodko]

I dunno but the first thing that comes to mind is water retention = frame death.

[tan top]

I dunno but the first thing that comes to mind is water retention = frame death.

      moisture trap !!    rust out  !!  

, oh crikey  if they are doing  that to new challengers ! thinking rotted out in 10 years or less &  unless they have galvernised diped it or something   ,  why do something as silly as that !!    

[Domino]

New has ecoating inside and out. IMO, All it would do on our frames is trap moisture against the unprotected inside and accelerate cancer. 
Besides, some sound deadening membrane inside the qtrs, doors,and floor pans will do much more for acoustics than the frame foam and is much less risky. Try that first, add the foam as a last resort!

[NHCharger]

I agree with the others, the spray foam could be a water magnet. I just installed a new trunk pan in my 68. While the pan was out I sandblasted the inside of the frame rails, painted with some SEM rust inhibitor then coated with some rubberized undercoating.

[71wrenchhead]

why not just use Great Stuff insulation spray 
thats waterproof AND gets EVERYWHERE!!!!!!

[70 Charger RT]

Thanks for the advice.  I think I'll coat it with POR15 and call it a day.

[elitecustombody]

why not just use Great Stuff insulation spray 
thats waterproof AND gets EVERYWHERE!!!!!!

It's not waterproof, it will soak up water if it comes in contact ,but if everything is sealed off and epoxied before application,it shouldn't cause any rust damage

OP, I believe Lord Fusor,3M and SEM makes closed cell foam,which will work just fine without trapping moisture,but the downside to using this product would be the high price per cartridge .Most companies had 30-50% price increase on most materials since January or this year .

I do not know if you knew, but some guys fill frame rails,rockers,pillars with this stuff to increase rigidity on track cars, it actually significantly improve structural rigidity.     

[71wrenchhead]

i thought it was waterproof? in anycase, i was just kidding, i think youll have much better luck with por15 and just taking your time in getting rid of all the rust in the first place

GOODLUCK!

[Silver R/T]

3M makes long spray wands that you can reach inside frame rails with. You can apply any coating inside frame rails through access holes on the bottom of frame rails.

[Calif240]

Eastwood also makes a special coating made for the inside of frame rails. It looks easy to apply and helps with rust prevention/treatment.
http://www.eastwood.com/internal-frame-coating-w-spray-nozzle.html
Looks pretty good for $20. I've had good luck thus far with Eastwood's products.
Hope this helps,
Terry