how far should i sand?

[Bandit72]

i'm getting ready to start on some body work on my car and get ready to start painting, but one thing i was wondering is how far should i sand down? to bare metal? to original paint? the car has all the factory paint/primer plus a layer of primer over the factory stuff and a THICK coat of black that someone sprayed on in the early 90's.

Thanks Ryan Olson

[bill440rt]

If it's possible, I suggest taking everything down to bare metal, applying a metal-prep chemical (mild acid-etch that removes small traces of surface rust), and applying a good epoxy primer, such as from PPG's DP line.
You can start your bodywork from there. The original paint is already 30+ years old. Why would you want to keep that as a base? It might be trouble down the road, & lead to peeling, cracking, etc.

[RogerDodger]

I have always taken mine down to the bare metal. You will find that the original paint will be very difficult to strip and will most likely need to be sanded down. If the bodywork needed is minimal and the paint is in good condition you may cosider leaving it. The most important thing is to expose any previous bodywork or rust and repair it correctly. It depends on what kind of job your looking to do.

[Silver R/T]

take it to the metal

[73rallye440magnum]

Bill- From what I've read in the past, doing the mudwork in bare metal gives a lot better adhesion then over an epoxy primer. (Such as PPG's DPLF line) Can you tell me anything from experience here? The PPG reps told me I'd have BETTER adhesion applying my mudwork over epoxy (of course they'll say that, they're salesmen) I just don't see that making much sense, what can you tell me?

[tan top]

take it to the metal

                

          i have always put bondo over bare metal  , never any problems & once you have finished that panel wipe some etch over it until you are ready to 2 pac primer it , then move on to the next panel , it seems to be the done thing   now-days in for some body guys ,to bondo over epoxy, but to me a old time body & paint guy  .. bondoing over primer is wrong . no matter what the paint reps say in my opinion

[GTX]

take it to the metal

 

          i have always put bondo over bare metal  , never any problems & once you have finished that panel wipe some etch over it until you are ready to 2 pac primer it , then move on to the next panel , it seems to be the done thing   now-days in for some body guys ,to bondo over epoxy, but to me a old time body & paint guy  .. bondoing over primer is wrong . no matter what the paint reps say in my opinion

When I was doing the GTX I found that at some point the rear quarter had been hit and there was bondo over the dent.
WAYYYYY too much bondo!

I took it down to the steel and along the way I found that they had slapped filler right over the original paint in some places and over primer over the original paint in others, too many layers of junk!
The filler was lifting from the surface since it wasn't a good surface to adhere to in the first place so it was a real good thing that I decided to go to the steel.
In some spots I could slip a putty knife between the body and the filler.

Do it once , do it right!