I’ve cleaned up the underside of my 66 convertible project (late 12/65 SJ build) to uncover as much as possible the factory colors, markings, sealants, etc., and have a few questions. Should I attempt to save the middle area, the drip patterns, sealant, where possible? Can the original primer be scuffed, prepped, and repainted with a light coat of PPG epoxy primer? Or should I just blast the whole underside?
First nice set of floor pans - sure plenty here will be envious at see these and how much work your going to save by starting with a solid original car
1- If you can make sure you have all the grease and gunk removed from the corners, cracks and surfaces the original finish can be feathered at any damaged locations, some of the sealers (like the front inner seat belt anchor locations - because of the production period) then scuff the original surfaces.
2- I would remove the pinch to rocker sealant before you do this and redo it after and make sure there is no surface rust in the corners or under some disturbed sound deadener outer surface. Also any spread on sealer that was originally applied after the red oxide. Your car has an unusual extra seam sealed by a line of chalking at the front edge of the rear shock mount/bracket to the floor. Haven't seen that before.
3- Also the surfaces just in front of the rear cross member will need more work since they got allot less primer sealer originally.
4- Rework the trunk drops
5- Check for extra holes and patch. Looks like there might be on in the drivers side front floor section
6- Deal with the surface rust in the rear wheel well at the center seam
7- Would also reproduce the galvanized surface of the dolly areas and make some dolly mark stand-ins to reproduce the factory circles you see now in the final product.
8- Touch up any damaged sound deadener in the wheel wells before hand - the brush technique with the Sludge will work very well in these situations IME. Then after the red oxide coat go back over the rear wheel well sound deadener and overspray on the floor and frame rail with some spray able, paintable undercoating so that it looks like it's on top of the red oxide. Then just finish with exterior color paint and over spray - then follow with the pinch weld black out
In this way you can preserve all or most of the factory drips and characteristics.
It looks like I’ll at least need to blast at least from the upper shock mount rearward and the firewall forward to get a clean surface. But the middle turned out pretty decent, except for that gaping hole that needs a panel welded in. And can the existing wheel well material just be cleaned, prepped, and repainted? Also, the same question for sealant (sound deadener) on the tunnel area where the floor pan meets the firewall.
Any tips or suggestions would be appreciated.
Yes you have plan. The section of sealer at the front of the tunnel (firewall to tunnel) is something the plant did from time to time where the panel gap was large and the spray sealant was used to fill in the gap. Remember to tint the firewall forward red oxide color slightly different from the firewall forward to reproduce the factory look. Does not have to be a dramatic difference
Hope this helps