Topic: Unibody Restoration: cut & weld before or after media blasting???

[Angela]

I'm looking for advice, tips and recommendations concerning my next project which requires significant metal work. Unlike my previous project which has zero rust, this car (70 Mach 1, not to be confused with the one I posted for sale late last year) has significant rust. It's not a basket-case by any means, but it's going to require much of the following to be replaced:
(a) Floor pans (both front sections beneath driver and front passenger feet area are gone. Driver's side firewall area of the pan is good; passenger side is very thin up to about the area of the heater core. There is one small hole about the size of a quarter in the driver's side behind the front seat, near the rocker. Rocker panels are solid)
(b) Trunk floor (there are holes in the trunk floor above both frame rails, yet the rails look good. There are also several holes in the flange around the fuel tank. The rest of the trunk floor seems solid)
(c) Firewall (see description in "a"... most of the firewall is solid, but there will be some metal needed that I don't think comes with the replacement floor pans)
(d) Door hinge area on driver's side (1/2" dia hole near top door hinge and the rust is spreading towards the pillar. I think a small section of this area will need work)
(e) Driver's side quarter panel (someone added mud flaps and they appear to have trapped debris and moisture, causing what I believe will be a small hole on the driver's side once the paint is stripped. The rest of both quarters appear solid inside and out. I think this area in question could be patched)
(f) Two, 2 SQIN sections of the tail light panel (there is rust-through at one hole around the tail light buckets, one on each side. I doubt this warrants a complete new panel, but it will require patching)

My questions are:
(1) Should I have the car media blasted FIRST, *then* start cutting out the floor pans, etc? -OR- cut out the rusted areas first, then have the body blasted?
(2) The floor pan is pretty bad, but other than that, everything noted above could probably be saved through the use of patch-panels vs replacing entire panels. I would prefer to retain as much of the original car as possible, but is it better in the long run to remove entire panels instead of piecemeal replacement?
(3) I could have sworn I recently saw a Mustang Monthly article concerning someone making a one-piece firewall-to-trunk floor panel... I cannot find the article anymore... has anyone seen this and if so, might you be able to post a link to the source?
(4) Where's the best place to buy replacement panels, especially given they're all going to be truck freight?

Also, if anyone knows of media blasting shops in the southeast MN, northern IA or southwestern WI areas, please let me know. I haven't yet been able to locate anyone in my area doing this type of work. I fear that if I hire a "regular" sandblaster, they're warp the remaining good sheet metal.
 

[TLea]

always media blast first. It will reveal other areas you don't see

[DM_1964]

always media blast first. It will reveal other areas you don't see

+ 1
Perhaps mark the panels you definately know you're going to replace (like the floor pans) so they are not blasted, that will keep your cost down...

[ruppstang]

+ 1 on blasting first. I took the floor out first then had it blasted so we could clean up area's other wise hidden. We used a new process of blasting with water and recycled glass. With the water there is no chance of warping the metal. It does require more work in clean up.

[TLea]

Regarding the floor/firewall pan. I've never used them but have judged several cars that were missing a lot of little details on firewall because it was repop
Not sure why you would have to replace firewall

[Angela]

Thanks for the advice everyone! OK, I'll focus on media blasting before doing much of any metal work. However, I do like the idea of cutting out known-bad areas before the media blasting, as "DM_1964" suggested, since that will allow the media to clean metal hidden behind.

Concerning Tlea's comment about why it would be needed to replace the firewall... it's not necessarily the firewall that is rusted, rather the very bottom of the firewall as it transitions to the floor pan. The floor pans I see for sale don't extend high enough up into the firewall, hence I believe I'll need to also buy a firewall and cut out and use the very bottom portion of it.

This is the 2nd time I've heard of the crushed glass & water blasting. I cannot find anyone in my area that provides that service. Is the sharp glass media a safety hazard when the blasting is completed? I know that no matter how hard one tries, it's impossible to get all of the media out of the car after blasting. I've always been afraid of glass as a blasting media but perhaps that's irrational on my part?

I used to see CJ Pony at a couple of the swap meets I attended annually and could order large truck-freight items such as floor pans and pick them up at the show to save shipping costs. CJ no longer attends these swap meets. I'm not aware of any other ways to save a bit of money when buying large items like this. I suspect it's going to cost close to a couple grand just in replacement panels, not including shipping.

[CharlesTurner]

It would be a much better job to replace only what needs to be replaced.  Do not get caught up in the mentality of changing out complete sheet metal sections, you'll lose a ton of original detail doing that.  Patchwork costs more at the body shop, but when going for authenticity, the extra cost will yield a much better car in the end.

Perfect example is the battery apron.  Most body shops will want to replace the whole piece when only the area below the battery is what's rusted.  It's tough to get a new panel to fit and spot welds appearing authentic.  Much better to cut out the rusted part and weld in a patch, preserving as much original metal as possible.

[drummingrocks]

Concerning Tlea's comment about why it would be needed to replace the firewall... it's not necessarily the firewall that is rusted, rather the very bottom of the firewall as it transitions to the floor pan. The floor pans I see for sale don't extend high enough up into the firewall, hence I believe I'll need to also buy a firewall and cut out and use the very bottom portion of it.

Angela, the section you're wanting is available separately.  It's called a "Toe Board," though I've also heard it referred to as a "Transition Pan."  Check on p.239 of the 2015 NPD catalog, part numbers 126-1ARH and 126-1ALH, $27.45 per side.   I had to section in those panels on both sides on my '69 Mach, and was pretty pleased with the overall fit (for a repro sheetmetal part, especially).

[nham3407]

Here is a link to the water & media based blasting. They offer listings of providers in your area.

http://www.dustlessblasting.com/

[DM_1964]

It would be a much better job to replace only what needs to be replaced.  Do not get caught up in the mentality of changing out complete sheet metal sections, you'll lose a ton of original detail doing that.  Patchwork costs more at the body shop, but when going for authenticity, the extra cost will yield a much better car in the end.

Perfect example is the battery apron.  Most body shops will want to replace the whole piece when only the area below the battery is what's rusted.  It's tough to get a new panel to fit and spot welds appearing authentic.  Much better to cut out the rusted part and weld in a patch, preserving as much original metal as possible.

Spot on Charles, something I've applied to mine during the sheetmetal replacement where possible.
Here's my battery apron (tray area) before during and after metal replacement. I'm really happy with the result.

[Angela]

Good point Charles; I have given a lot of thought to your comment and have decided I agree with you. After the body has been media blasted I'll see just how much I can save through the use of smaller replacement panels.

While looking at the floor pan path panels sold through NPD, I noticed that they all say "ribbing correct for 65-58". That's going to pose a problem for my '70 application. Does anyone have a source for "correct ribbing" floor pan panels for 1970? Also, does the same statement hold true for the one-piece floor pans; i.e. even if I were to order the one piece panel, does it too have the incorrect ribbing? Or is this just a problem with the panels NPD offers?

[J_Speegle]

While looking at the floor pan path panels sold through NPD, I noticed that they all say "ribbing correct for 65-58". That's going to pose a problem for my '70 application. Does anyone have a source for "correct ribbing" floor pan panels for 1970?...........

Did you happen to see/read the article in the Library about modifying/fixing the 69-70 floor pans?

- Fixing Reproduction Floor Pans for 69-70 written by Pat Whalen

[Angela]

Wow, thanks Jeff! No, I had not seen that article.... way cool!

The author makes reference of "donor" panels to get the correct ribbing.... which is basically my question: where are you guys getting panels with the correct ribbing floor pan sections? Everywhere I look (or call) they tell me their floor pan parts have the correct ribbing for 65-68 only. Ugh.

[midlife]

Angela:
I think the donor floor pans come from Mustangs that have been parted out.

[J_Speegle]

Allot of restorers are now choosing not to replace the whole pan but sections as needed since the factory welds are so hard to get right. Also saving good sections provide a guide for the floor color, overspray patterns and such to be used later