PDA

View Full Version : Firewall Prep



Tom Bovay
04-20-2015, 05:33 PM
I'm new to the whole bodywork thing so I thought I could cut my teeth by starting with the firewall and inner fenders. I really don't know what I'm doing so any advice this forum would be much appreciated.

I have started by degreasing everything and then used a brass wire wheel to take as much of the rust off as I could and get it down to bare metal. The wire wheel was going really slow so I switched over to an 80 grit sanding disc on my angle grinder. This worked very quickly to take it down to bare metal but I was worried that it was taking too much off and thinning the metal. I did a small section and then decided I would ask some questions before I went any further. Does anyone have any recommendations on sanding material and techniques?

I also have several small dents in the firewall and wasn't sure how difficult it would be to fix.

4343

JT56
04-21-2015, 05:16 AM
Welcome to the site Tom, glad your here. On mine I welded up the holes, then used a grinder then applied the Evercoat below and sanded to a feather finish. 3M has some similar products too. I'm no expert, but I believe the dents are shallow enough you can use the Evercoat on them. First clean them up real good mechanically (wire brush/sanding), then clean off with Prep All, apply Evercoat, sand, Prep All then sandable primer, Prep All then ready for paint.

http://www.evercoat.com/imgs/products/100425_LMetal-Glaze-ULTRA-pumptainer.jpg

chevynut
04-21-2015, 08:52 AM
It all depends on how much of a quality job you want to do. Obviously there are a lot of shortcuts you could take, and it all depends on your budget and resources (tools, etc.) that you have.

For a quality job, the first thing I would do is weld up any holes you don't want, grind the welds smooth, and fix the dents using hammer and dolly. For larger holes, use sheetmetal plugs and weld them in. Be careful not to stretch the metal while hammering and get it as close to smooth and as straight as you can before using any fillers.

Next you need to make sure you have ALL of the rust off before you apply anything over the metal. If you have compressed air, I recommend sandblasting the entire firewall with fine sand or having someone else do it. I use a cheap Harbor Freight pressure blaster with medium silica sand and it works great. Soda blasting won't take rust off. Be sure to also use some good oil and wax remover or even acetone before putting anything on. You want it to be clean and oil-free.

Once the metal is all clean, you can do whatever filling you want with a good polyester filler(Like Evercoat Rage, or others), then sand the filler and feather the edges out. Next prep the metal with a metal prep solution like Evercoat's "Metal Ready" or PPG's metal prep DX579. After drying, apply some good epoxy primer to the entire firewall.

Some guys recommend epoxy before any filler, but that's been a subject of a lot of debate. I think either way works fine, the only downside is if you apply epoxy first you will have to apply it again because you'll sand it off at the edges of your filler.

Once the firewall is in epoxy, I recommend a product called Slicksand by Evercoat. It's basically a sprayable polyester filler and high build primer. This will cover the epoxy in case it has a re-coat window, and allow you to further smooth out some defects. You can apply several coats of Slicksand if needed, depending on how straight you want things. The nice thing about Slicksand is that it applies easily and uniformly, it's very easy to sand (after about 24 hours) and it's pretty cheap. Finally, once you're satisfied with the smoothness, apply your final primer/surfacer that will go on just before your paint.

This sounds like a lot of work, and it is. But imo it's the best way to do it. Again, you can cut a lot of corners, use cheaper materials, but the job is only as good as you make it.

I just finished doing this on my firewall. I had replaced it some time ago with a custom one I built and metal-prepped and epoxied it with PPG DPLF. I had to sand it to scuff the epoxy and remove it completely in some areas so I could do some metal shrinking where I had some warpage. Then I had to apply another coat of epoxy, apply the slicksand a couple of times sanding it between coats, and finally got it into the final primer a couple days ago.

chevynut
04-21-2015, 08:55 AM
Welcome to the site! Don't be afraid to ask more questions too. We've all been there. ;)

JT56
04-21-2015, 09:08 AM
Cant stress cleaning/prep. Particularly in the engine bay. This is where most of the oil/fluids are at and unless its removed it will react to the new paint and/or come back. Keep us posted and we like pics too

chevynut
04-23-2015, 07:39 PM
Tom, I was curious what you ended up doing. Here's my firewall prepped the way I described.

4349