Thanks.
Fritz, do you know if they had the car stripped of all paint when they did the job in 1985? Did you strip it to bare metal commpletely this time?
I had some older pictures of the car taken during that restoration (in 1985) and it appears that it was taken to bare metal, other than the hard top (more about that later). We had to do major body work (replaced bottom side of both rear fenders and the entire bottom and inner support across the rear (below the deck lid). We took eveything down to bare metal on that part of the car, including the rear quarter panels. The rocker panels needed some repair at the ends, so these were taken to bare metall as well.
The other areas (previously painted with lacquer in 1985) were sanded down close to bare metal, but since the hood, deck lid and doors were aluminum, and since the existing lacquer paint was intact, we went
easy on those parts (sandblasting of an aluminum part is out of the question, due to possible warpage; and paint remover is messy stuff, so we avoid that). All that was left were the front fenders, and i am not sure how far our body man went on those - I was not present and he is out of town this week. He did say that there were no damage or rotted areas in that area of the car, and if so, know that he would have let me know and would have made major repairs (he uses real lead over welded repair panels). If no prior repairs, I imagine that these front fenders were not taken to bare metal, but I leave matters such as these to our painter, based on his years of experience.
I know that we use epoxy gray primer (mixing in a hardener). After spraying the primer, the car is block sanded for days to be sure of no high or low areas and then primed again, sanded again, etc. Our body man then sprays a very light coat of black primer over the gray primer and sands again. The two colors show up any high or low spots and if any, they are corrected. Then the final sealing coat of epoxy primer, which is thinned down. After that dries, the base coats are applied, followed by many coats of clear coat. Then this finish is sanded with finer and finer sandpaper, and buffed to a mirror-like finish.
The finish on this car is probably better than original. You will have to decide the look that you want. Since my wife's car is not being judged, we went for a high shine.
The hard top gave us some trouble in that we did not want to remove the headliner to remove the two chrome strips, so carefully masked them. After painting, we had some minor problems along the edge of the chrome strips, so ended taking almost all of the surface down to bare metal, sarting all over on that part of the project. At that time, saw the original white finish under the silver paint job from 1985). Too much paint caused rough edges next to the chrome strips. Luckily the top was sanded, primed and painted while on our bench, so sanding again and repainting a second time was not a big deal. Attached are a few more pictures.
My recommendation agrees with that of your painter, but depends on how much paint is on the car, what kind of paint, and if any previous repairs - Unless you feel certain of what is under the existing finish, I would go by your painters advice, as you don't know what you might find. (Be careful with the aluminum hood, deck lid and doors, as they can easily be warped). Since your painter recommended taking the car to bare metal, he probably has his reasons. Every car is different. We once stripped down a 1939 LaSalle that had the original brown etching primer that defied paint stripper. Rather than sandblasting it off, we opted to leave this primer in place as a base and then sanded it smooth, applied more primer and then lacquer paint, and it came out perfect. Some of the old factory primers served a purpose and sometimes the best plan is to leave that surface intact. (This does not apply to any paints applied later over the original primer - better to remove that paint, especially if enamel). Most lacquers, and some of the urethane paints used today will lift enamel. That is probably why your painter specifically asked if the paint was enamel. Another thing to consider is the age of the existing paint - if recently repainted and you don't know what type of paint was used, better to get it all off. In our case, since car was taken to bare metal and then painted in lacquer almost 30 years ago, we felt that complete removal was not necessary, except in areas that needed repaired.
On the 280 SL, removing the side chrome strips on the doors can create a headache, as the screw holes can be enlarged during the removal and replacement process (aluminum is weak as compared to metal). There was another thread about this on our forum recently that covered this nicely. Good luck on all of this - sounds like you are doing it right and advance planning saves a lot of headaches later.
Fritz