I currently have my 70 body off the frame and am ready to begin cleaning up the underbody of the car. What lengths do I have to go to before I paint and what paint is best to use. Do I just need to scrape off the loose stuff and coat with POR. Please share what you all have used.

Thanks

Ryan,,,This may not be the answer your lookin for but this is the best way to do the bottom of you car. Sand, blast, scrape, or whatever it takes to get it to a point where it has little or no paint left on it. Then prime it with etching primer, and top coat with black enamel with a 60% gloss.. Heres mine before the top coat...
http://www.chevelles.com/showroom/data/500/68body.jpg

Mine too!!

i would like to do something to the underside of my 69 chevelle also. there is surface rust under the whole bottom of the car. i dont want to take the body off.what to do????????????????????????????????????????/

i would like to do something to the underside of my 69 chevelle also. there is surface rust under the whole bottom of the car. i dont want to take the body off.what to do????????????????????????????????????????/
Do the same as described above. Just do it with the car up on jack stands. You will have to work around the exhaust, cross member etc. It may take a while, but you want it to look good, right??. You will be happy with the results.. :D :D

what is the best way to get my car on it's side to paint the bottom? the car sitting on jack stands now and I have it almost ready to be painted. I have a little bit of rust repair yet to do then ready for paint. I have the car striped of every thing that is bolted or screwed in place. I know the best thing would be for a rotisie but now that I aready did all the hard work without it, would be pointless.

I don't recommend this but you can do the same thing I did with my 70 Monte. I sprayed it on my back, definitely not fun, but it was much easier than the cleaning/sandblast/rust repair part. It turned out very nice but I'll never do it again. I'm going to use a rotisserie on the Chevelle. I painted it using a 2-gallon pressure pot so I didn’t have to stop for refills and it also helped not having the quart cup in the way. Just make sure you have adequate ventilation, lighting, respirator, safety glasses, coveralls, etc. You can see pics of my Monte undercarriage in the TC showroom in the non-Chevelle related section. Good luck, and most importantly, be safe!

you said you sprayed it on your back. do you mean that you sprayed(what?) over the rust.??

When I did the Camaro last winter, I did everything on my back. 3m stripping wheels in a die grinder will take off just about anything in a heart beat, went through a dozen of em. wire cop brushed for the nooks and crannies. Then 2 coats of por 15 and 2 coats of chassis black, all brushed on. What a nasty job!

Just got through with mine. What a crappy job that was! I did it on a rotisserie, which made it much less crappy, but it still was. Used diesel fuel to soften the undercoating. Patched a couple holes, sanded with 150, again with 220. Blew it all off and wiped it down with lacquer thinner. Used self-etching, non-sanding epoxy sealer, then painted everything Astro Blue.

you said you sprayed it on your back. do you mean that you sprayed(what?) over the rust.??

My car is on jack stands with everything removed from the body, pretty much just a body shell bolted to the frame. I built a plastic booth around the car, and carefully covered everything on my car and garage that I did want sand in. I started by scraping off all the rubber undercoating and grime that I could, and then sandblasted the bottom and frame. Once I was satisfied, I cut out and repaired the rust areas, prepped and sprayed 2 coats of por 15 and 2 coats of chassis black.
If you just have surface rust, (not thick scale with holes) then por 15 (por=paint over rust) will be fine. It designed for seasoned metal, just follow the instructions carefully and don't get that stuff on you!