Folks are always asking about this, so here are some basics & part numbers.
- On the SMC fiberglass (hoods & roof panels), always use a product specifically made for SMC, such as "Vette Panel Adhesive/Filler". I use "Fiberglass Evercoat" part #870. As the name implies, you can use it for filler or for bonding SMC panels - as well as other fiberglass panels. Always grind out the damage (or surface to be bonded) with 24 grit discs. Fill & rough-in using 40 grit, finish with 80 & then 180 (always use some type of block to get the flat surface/contour).
- On the bumpers (which are "RIM"), SEM part #39708 works well. It should also work well on "RRIM" panels - the door skins, fenders, & 1/4 panels. When repairing damage, SLOWLY grind the back of the damage with 24 grit discs. If you grind too fast, you'll melt the material & close the pores & nothing will stick. Chop up some fiberglass mat with scissors into 1/4" strands & mix with the repair material, fill to 1/8" thick at the repair, at least 1" beyond the damage. Once that dries, "V" out the front of the damage/tear with a small grinder using a 24 grit disc. Fill that with the same material; 'glass strands not required but will add strength. Grind/sand/finish down to a final grit of 180 & prime.
- If you need to strip old paint off (only necessary if the car has been painted since it left the factory), you can use chemicals if you're very careful. "Aircraft Stripper" is the best brand name for strong stripper. You can use this on the SMC panels, but be careful not to get any on bare panels/exposed SMC (& follow all instructions). It can also be used on the RRIM, if you're VERY careful not to get any on the bare panel (exposed plastic). "Bumper Stripper" (comes in a spray can) can be used on the RIM (bumpers) & the RRIM panels. You still have to avoid letting it soak into any bare spots. The paint store I use carries the "Bulldog" brand of bumper stripper - product #EUP367.
You only need to use chemicals to save time if the paint is too thick to sand off "eaisly".
- If the paint is not too thick or it still has factory paint (or after you use a chemical stripper), sand it with 180 dry on a DA. Factory paint only needs to be sanded smooth, feathering any edges that go through (or where clear or color is flaking). Hand sand everything you can't get to with the DA, using 180 dry or 320 wet. An alternative if you don't have a DA sander is 180 dry or 320 wet by hand, but it'll take a long time to do the whole car (wet sanding is faster).
- Rough in repairs (fillers) with 40 grit; finish repairs with 80 grit & then smooth somewhat with 180 grit. Don't smooth so much as to dip out the surface below level.
- Cover the entire car with PPG epoxy primer. I use the DP50LF, with DP401LF catalyst. The 401 catalyst is recommended for flexible parts (read the tech sheet it has an induction period). You can use 402 catalyst on everything except the bumpers (no induction period). OR: epoxy prime just the damage/repair areas in order to help the high-build stick (in the next step), & prime the whole car after blocking that out.
- On any filled/repair areas prime with high-build over the epoxy (if your repairs are a little rough). Brand depends on your local paint store. Any good brand-name catalyst-hardened high-build should be fine. You can shoot that over the PPG epoxy within 20 minutes, or wait a couple days. After that, sand the epoxy with 180 wet before shooting the high-build. You can shoot the high-build over the entire panel, if it's wavy & needs blocking to flatten it out. But DON'T build up the high-build very thick on any flexible parts. Block the high-build primer with 180 wet using a paint paddle (on "flat" surfaces) & a dense sponge pad (on the more curved surfaces). I use 3M pads #5526 & Mirror-Glaze pads # E-7200. Use a "guide coat" of flat black spray paint LIGHTLY dusted on the area to show up the imperfections when sanding.
- If you have imperfections that the primer doesn't fill (ie you can still see the guide coat in them after blocking), scratch them out with 80 grit & fill with a good catalyst-hardened putty/glaze; I use "Fiberglass Evercoat" part #416. Final finish that with 180 wet. Always use a paint paddle or sponge pad (or similar block).
- If you have the rest of the car smooth, re-prime just the area of the repairs with the PPG epoxy primer. (Or if you've only epoxy primed the damage, now prime the whole car.) Final sand the whole car with 400 wet & shoot your base/clear. If you REALLY have the car smooth before priming, you can shoot over the epoxy primer after 20 minutes without sanding.
- Type of paint will depend mostly on your budget & local paint store. If you want the best, use top-of-the line PPG (Ditzler) or Sikkens. Be prepared for sticker shock. A good cheaper paint is Dupont Nason. Always use base/clear for the best looking, longest lasting paintjob.
- For buffing, I usually sand the clear starting with 1000 wet (again on paddles & sponge pads) to get it flat. After that, sand with 2000 wet on a sponge pad. Alternatives vary with the brands of clear: Sometimes you can just sand it with 1500 dry on a DA & buff. Buff with a white sponge pad (I use 3M Perfect-It #5723) on a buffer using 3M Perfect-It compound #6085 or #6062. On harder clears (or if you haven't sanded out all of the 1000 grit scratches), you may need a higher-cut compound #5936. Final polish with black sponge pads 3M #5725 using a good "machine glaze" (I use 3M #5996 & other similar alternatives) or "Foam Pad Polish".
NOTE: Most sandpapers are pretty much the same as far as grit, except for some cheaper brands which you have to be careful with (1000 wet may leave 800 scratches). Best to buy 3M brand, but to save money ask your supplier about the quality of the sandpaper he stocks.
* Most all aftermarket fiberglass parts will need to be epoxy primed & high-build primed to block them out smooth, then of course a final coat of epoxy to seal it.
* Adding the final coat of epoxy as a sealer also helps with adhesion of the paint. If the surface is smooth, you can start shooting paint over the epoxy without sanding as soon as 20 minutes. If it's not quite smooth (or if you want it really slick) you can wet sand the epoxy primer with 400 before painting.
* I do NOT suggest bonding any parts such as fiberglass to the RIM or RRIM panels. They have vastly different expansion rates & will most likely crack out. You MAY get away with bonding pieces of the same materials together, but the flexible shtuff is still iffy. If you try it, use the above product specifically for that material. ** Slight addendum... I'm making fiberglass fender vents & they seem to work well bonded to the back of the fenders with the SEM part #39708, if you grind the surfaces with a 24 grit disc. I still don't recommend you bond large parts to the plastic panels.
** New info: For the semi-flat black parts (engine vents) SEM (brand name) makes a "Hot Rod black" kit HR010 that has everything but the sandpaper & primer.
***More info: For maximum adhesion on hard plastic parts (like side moldings & interior trim) you need to use a primer specifically made for plastic. I use PPG part #DPX 801 . A light coat (it's very thin) will actually soften the plastic so the paint will melt in. With that any good brand name semi-flat or satin black will stick. "Trim black" & "Bumper Coating" are usually made in a semi-flat formula & should look great. Always try a test panel if you're trying to match another piece.
HTH,
~ Paul
aka "Tha Driver"
