Body Shell Refurbishment Advice Needed

[T_Dub]

Taking opinions here while I have time to make up my mind. I have a lot of work to do to this shell, no doubt. One of the things I've been considering is completely stripping the shell to near bare metal, including popping off the sunroof cassette so I can get at the join between it and the roof skin.

I have a couple reasons for this:

• I have quite a bit of work to do on the underside, I'm going to replace the front floors wholesale just to get back to good metal.

• The factory undercoating is very old. Can it withstand another 30 years?

• The sunroof cassette and the roof skin has rust where the two meet. How long before it penetrates the roof, even if I prep it as best I can?

• This is be a lifelong car, the repair work should last 40 years. It will be in a heated garage for the rest of its life, and not driven at all from Nov-April. That said, if its outside at all it will get salt spray and water hitting it often.

Basically looking for your experience here.

• How hard is the stock undercoating to remove? Tips and tricks?

• Has anybody seen rust under "good" undercoating?

If I bite the bullet and do this, I will take the bottom of the car to bare steel after the rust is fixed, prime, and coat with Raptor/Gravitex coating, up to the line on the rocker. Great thing about this stuff is it takes colour well, so the colour will go down to the bottom of the rocker. Then the car proper will be seam sealed and professionally painted inside and out. Then all the cavities will be waxed with whatever I think is best at the time, and plugged properly.

Pics of the car in the projects section for reference:

viewtopic.php?f=112&t=279898

[flybynite]

Factory underseal: pig to get off no two ways about it. Needs a "twisted" wire brush angle grinder, heat, scraper, ear plugs under ear defenders lots of time, even more swearing. Only other way is to dip it as most blasters will not touch it and those that will likely to warp your panels.

I doubt you will find corrosion under good underseal, but telling what is good is the problem. There is often rust lurking between the body and brackets spot welded on.

If there is rust around the sunroof, now is the time to do it if this is a keeper. Done now it will last the life of the car. Have a look at this on what is a sound M3

viewtopic.php?f=112&t=266832&start=105

I will be doing that to both of mine, one is rusty, the other one isn't so much.

On a proper resto most people use the 2-pack 3M bag (08800) system and paint it. More expensive than Gravitex but more like the original. I like gravitex but it can go hard and brittle.

Good luck with it

[T_Dub]

Thanks so much for that. I've been told a bunch that it's not worth prying out the sunroof tray. I think the problem is that most people in North America don't experience the weather that we do. Newfoundland is much more comparable to coastal northern Scotland than most other places in NA.

[T_Dub]

I've been counseled by some to look at acid dipping the entire shell. I have to say it's appealing, if it was local I'd be all in. But I would need to bring the car to Toronto, 3000km away.

Still, I'm considering it.

[MikeBM299]

With regards to the underseal I'm currently contemplating on what I will be using for my resto too. I currently have my eyes on this Wurth Product: https://eshop.wurth.co.uk/Product-categ ... en/GB/GBP/

Looks wise I think it's very close to the factory one and does not cost as much as the 3m does while offering good protection too. On the plus side it can be painted beige to replicate the original.

Does anyone have any experience with it?

[flybynite]

I've been counseled by some to look at acid dipping the entire shell. I have to say it's appealing, if it was local I'd be all in. But I would need to bring the car to Toronto, 3000km away.
Still, I'm considering it.

Whilst it may seem like a good solution there are problems with acid dipping.

1. The biggest problem is acid weeping from joints into your new paintwork. The shell has to be thoroughly cleaned afterwards and even then there are no guarantees. Some body shops will not touch a dipped shell because of this.

2. It can leave bare metal in places you cannot get a covering on. An e-coat is the best way but again no guarantees.

3. Ideally it should be a 2 stage process, dip it to show the problems, then dip the repaired shell again to clean it before priming or e-coating. Not ideal if you are 300km away.

There is a different way that uses heat to burn off the paint but there are reports of panels distorting and it is really expensive, but so is proper dipping, cleaning and e-coat.

Looking at your shell, I think it is not so bad and the work in hunting down the rust, grinding it, treating it and etch prime is still less than re- seam sealing an entire shell but it is never an easy call.

[T_Dub]

Looking at your shell, I think it is not so bad and the work in hunting down the rust, grinding it, treating it and etch prime is still less than re- seam sealing an entire shell but it is never an easy call.

This is the kind of experience in looking for. I think Barry's process on the M3 is what I need to do. The sunroof tray needs to come off to ensure I don't get rust through the roof, but on the underside I think I can fix most things and re-coat.

Looking inside some of the frame rails, it's really cool to see the pristine metal and Cosmoline. Probably best to leave that alone like you say.

[T_Dub]

While we're here, whats the general consensus on deleting the "jacking pads"? I think I'll coat them well enough that they'll last this time, but if they really arent necessary I'll save the expense/hassle. Better to keep original in case of future sale?

[JungleGus]

I am not sure how helpful this is, but have a look at some of the Retropower bodywork videos on YouTube - they have some really good processes to ensure logenvity (zinc spraying, etc.).

As for acid dipping, I believe the general consensus is that it's very very difficult to get right, and the risk of it coming through later or being left in places you can't see is high.

Jacking pads - ideally re-building them. But if you're putting this much effort into a keeper - I wouldn't worry about re-sale.

Very best of luck! Bodywork is not fun nor cheap to do right

[DanThe]

There are several bodyshops round here that will not get involved with acid dipped shells, they all have horror stories of classic cars that have gone wrong.
Blasting is the way to go in my opinion

[T_Dub]

Thanks folks!

I have definitely watched retro power, and would love to have that kind of job done.

Follow up question would be, how to get the underside of the car blasted properly? Something like a paint stripper to get the majority off, and then blast it?

If blasting the underside is not going to happen, I think using Barry's M3 as a guide would be my plan.