Seam sealing, primer and undercoat

[Shel Hart]

Structural work is done and very proud of our year anniversary of beginning this. Floors in, seat mounts in, pedals, foot board mounts, diagonal brace and battery box in place and look exceptional. The folks at restoration design were super helpful with exact pics and detailed dimensions and zims great for new tunnel cables, transaxle mount, etc. Now to determine seams, primer and undercoat. Questions:
1. Seam sealer brand? Apply on bare metal? Thickness to replicate factory?
2. Epoxy primer - Black for interior cabin and undercarriage and then color match trunk and engine compartment? What did factory do?
3. Undercoat- best brand? Thickness? Don't have anything to hide but also would prefer a little added protection.

As a data point, I'm restoring car to original ivory color and red leatherette interior. Trying to keep as original as possible. Thanks for any suggestions and wisdom!

[Ned Gorski]

shelhart
with the cabin and the underside hood and trunk
i applied an etching primer primer the week prior to starting the sealing and epoxy. i wanted a 100% coating on the bare metal .. i brushed it into every crack and seam, then sprayed and or brushed everything with the epoxy primer .. I then used a 3m seam sealer then sprayed wurths ssk. 6 coats on the underside 3 under the hood and 3 in the engine compartment. I used about 10 or 12 cans.. The trick is to spray the wurths soon after you apply the epoxy and seam seal... you want to get the under coat (wurths) down before the epoxy is fully cured. Just try and complete it all in one day..The sks sets up after a day but takes about 3 weeks to fully cure... and get really hard... great product goes on nice and is easy to clean up . I was told if your epoxy fully cures prior to spraying the under coat you need to rough it up because its so hard the undercoat will not stick well. hope this makes sense

[Dennis ODonnell]

Slight hijack: Earlier A cars like mine have mica or something in the original asphalt undercoat, Wurth is nice but looks like plastic. Anyone have a mix/ topcoat or additive to mimic the original '50s material appearance?

[Steve Harrison]

I know exactly what you mean Dennis,...I scraped tons of that stuff off myself.
I hope it was micah, and not asbestos, haha. I saved a little bit of it for future testing, but maybe I don't want to know.

I got a tip from Lowell Sivey, an old school restorer in Ohio,...Roofing Tar!
They make a type with a fiber reinforcing additive. The fiber stuff gives it that real lumpy "pre A" look that the original undercoating had. You have to thin it down with thinner to get it to spray through the Eastwood undercoating gun, and even then I had to 'poke' the wand occasionaly. And let me tell ya,..it is hands down, bar none, easily, the messiest PITA job I have ever done on a car. I had tar all over myself, in my hair, back, etc. It also took a long time (think weeks, not days) to dry and settle down, and then I painted over it with black paint, brushed. It looks like a fair approximation to the original, but maybe not as thickly put down. Some of the factory stuff on my car was downright thick, and in sagging sheets in places. I think they were trying to get it to do some sound deadening as well as water barrier, it was on that thick.

The later cars like the one here under restoration I don't think had undercoating as thick, but I don't know the later cars all that well.

[Steve Harrison]

Oh yes, and I second the 3m seam sealer.

And, as far as first coat from bare metal, what I did was use a metal prep wash recommended by PPG and went over that with their epoxy sealer. (DPLF)
From there you build your primer coats (k36) and finally, color.

But you will find that there are as many different regimine's for body/paint work as there are folks who do it. Just about all will have merrit. You'll have to ask a bunch of people, distill their answers, and come up with a plan that works for you. Your paint store will also have some advice, just be sure to tell them you're not looking for the cheap way out, but rather for the system with the best longevity, etc.

[Matthew Devereux]

Your choice for bare metal is self etching primer or epoxy primer (at least when I last talked to the auto body supply store). All welded joints were coated in copper based weld through primer. I use self etching primer on smaller pieces like tin and wheels. I used a General Paint industrial metal paint for the underside and then a spray on rubberized undercoating on top of that. Is it like the factory? Probably not but it should last forever. Slathering tar based undercoating on bare metal seams might be correct but I wouldn't do it

[Dennis ODonnell]

Thanks, Steve. I'm using black PPG epoxy primer and am thinking of a very dark grey, flat finish top coat with some sort of mica added. Think I'll pass on the tar baby stuff.

[Steve Harrison]

Ha Ha, yes, it was kinda like the tar baby approach let me tell ya.
I am interested in how your coat goes with the mica added. You will most likely have to experiment with both the thickness and equipment. Spraying anything with 'lumps' in it is a challenge, they pack up, don't stay in suspension, floculate, etc.... I'm sure there is equipment to do it, heck, Porsche did it originally right? But without that big ole' specifically engineered commercial gun, it will likely take some experimentation. Screening the pieces for size and uniformity before adding them might help. Do post with how the process goes and how it turns out, yes?

[Alan Lay]

You will be getting to the point where everything is clean and more fun to work on.

Here are a few photos of before and after of my coupe going back to ivory and red.

Good luck,
Alan