Underbody Cleanup/Rustproof

[69fourspd]

Here is my question - any ideas are always useful.  I am cleaning up the underside of my 69 Charger, and looks to be pretty clean.  The factory undercoating is still on all floor pans and is in decent shape.  It looks like the previous owners stripped most of the frame undercoating.  I was thinking of cleaning off all of the frame and hitting it with Por 15.  I don't want to strip the pans since they have made it 37 years and have been protected well from the undercoating.  If I Por 15 the frame, and cover the POR 15 with Shutz, should I just clean off the old undercoating and apply schutz to thin areas and bring into the frame for a uniform look? What would be a good cleaner to use on the undercoating to prep the surface for schutz? Has anyone done this and is it recommended for rust prevention?

I have read this post http://www.dodgecharger.com/forum/index.php/topic,10801.0.html and I would say that I have not encountered any loose coating underneath.

[resq302]

Well, if you want to be politically correct, the factory never (to my knowledge) undercoated the entire car.  They only undercoated the wheel wells.  Usually, back in the day, dealerships would undercoat the car at an additional charge or throw it in at no cost as a dealer "freebie" to make the sale.

Again, if I am wrong someone correct me.   My wife does all the time!

[The Ghoul]

its going to be though to hurt the por-15 when it cures, so Id guess just prep the way the manufacturer suggests..
Por wants you to rough up the surface before painting, I dont know if that goes for undercoating as well.

[firefighter3931]

POR-15 needs a rusty surface to adhere to or it will peel and flake off. If you take it down to bare metel the best thing to do is soak it down with water and let it flash rust. I know that sounds a bit crazy but that's the only way it works...trust me i've tried it.

I used a product called ZERORUST on the underbelly of my 68 RT and i'm very pleased with the results. It has a semi gloss finish and applies well with a spray gun. You can paint over any surface as long as it is clean and dry....bare metel as well. I was in the same boat as you and did remove all the factory undercoating and resprayed it with the Zerorust product. I'm gonna spray some 3m rubberized undercoating in the wheel wells for rock protection and sound deadening.

I like using the POR product on suspension stuff : axle housings, leaf springs, shock mounts, brake drums, backing plates etc...But the surface has to be properly prepped for good results. 

Ron