Topic: Thoughts on Underbody Work - 69 Boss 302

[Aussie_Boss302]

I'm interested in some input regarding my Acapulco Blue, 69 Boss 302.  It's been parked since 1979, but it's a northern car so there are some rust spots... overall, I consider the body to be pretty solid.

So far I've stripped the interior and removed the tank, exhaust and rear end.

I'm about to focus on the under body.  Initially, I was going to have at it with a wirewheel on a grinder and then shoot the underside with epoxy primer.  The goal is to get the Boss back on the road and now is not the time for a full blown restoration.






Now I'm intrigued with what's under the sound deadener.  I'm thinking about scraping it away to reveal what the factory applied... where there's intact sound deadener the under body paint seems "preserved".  Obviously, where there's surface rust I'll need to wirebrush and perhaps spray on rust encapsulator.  What's the best way to remove the under body sound deadener?  Does it look like a waste of time and effort to go this route?

[midlife]

Sound deadener comes off fairly easily with kerosene or gasoline with elbow grease and a rag.  Do this in a well ventilated area and be prepared for several gallons of gas.  It is tedious work, but does not harm the original finish. 

[J_Speegle]

Expect that you might find what is left over of the batch/mixture epoxy primer and paint brew

A few things to consider

- A grinder is not going to get in all those corners and along all those panel lines. Might mess them up in the process

- Also consider in those panel overlaps - example rear frame to trunk floor - there is likely rust growing somewhere in between the panels

- Lastly please - please don't go the "rust encapsulator" route. Too many stories of the rust continuing to eat away under that hard coating. Its a mess to apply and difficult to over coat so you'll end up with a silver, red or black undercarriage.

As a side note - will be interested once you get going to know if the rear shock cross member is hand welded along the edges to the floor in places - skip welded?

How it the best way to remove the factory sound deadener and even aftermarket undercoating? Try the search feature - plenty of prior threads and currently member - dsielke is making great strides in his efforts in the thread below

http://www.concoursmustang.com/forum/index.php?topic=16728.0

[Aussie_Boss302]

Thanks gents.

Dsielke's efforts look well worth it.  I'll give it a try and see what's underneath the sound deadener.

I'll be sure to post pics of the rear shock cross member.

As for the areas with surface rust, what surface preparation and finish would be best?  I'm hoping for something that would "blend" in, not be detrimental to future restoration work, and prevent future damage?

[Aussie_Boss302]

I’ve got a few hours removing the undercoat.  It is slow tedious and dirty work, and some sections look really good... my slop grey is very blue.

However, in reality there are more area of surface rust vs original underbody paint.  I think it’s best to try and mimic the factory underbody paint.

What’s the best way to strip the underside to bare metal (media blasting isn’t really an option)?  Large areas I can get to with a wire wheel and grinder.  Some areas I can get to with a heat gun and scraper.  What about using paint stripper?  Thoughts about stripper residue in the lap joints?  Ideas about stubborn underbody coating in the lap joints?

[J_Speegle]

Is this car/body jacked up on jack stands or on a rotisserie?

[Aussie_Boss302]

On jackstands

[J_Speegle]

On jackstands

Well based on what you've shared so far I don't think you have any easy ways out other than the combination of different processes (chemical strippers, wire wheels and elbow grease) you have already identified.  Would be careful to not cause more work (grinding marks, chewing/grinding off edges, thinning metal) later if you get to carried away and impatient with the process.

Noticed the other day the Evapo-rust now makes a gel. Haven't tried it but it might be a product you might consider to ally over the bare steel (or almost bare) when you get there to remove the last hidden rust int he corners, along edges and so on before you switch over to reapplying primers, sealers and paint.

[Aussie_Boss302]

I had a productive day.  Up to the back seats and between the frame rails is clear of sound deadener. 




During the day the slop gray looks more green than blue.

In my opinion, Mineral Spirits works best, followed by Kerosene and then WD40.  I expect gasoline works really well but I'm not game to use it.

I soaked the undercoating with mineral spirits, let it sit, and used a heat gun & scraper to remove the majority of it.  The epoxy primer is pretty tough and I cleaned the residual undercoating with a scotchbrite pad and solvent.  I'm going to attack the undercoating at the seams with a brass bristled brush and solvent.

The plan is to apply epoxy primer to the underside, followed by paint color matched (approximately) to the slop grey. 

Evapor-rust gel I'll need to look into.  Has anyone had success with Eastwood's rust converter?  I'll probably hand sand the original epoxy primer to accept the fresh primer... there seems to be more bare metal than primered surface.
 

[J_Speegle]

Care to share when the car was built?  Just tracking time periods and floor coloring (as well as a ton of other details)

You doing everything front to back or only from a certain location?

[Aussie_Boss302]

9F02G186574 was built in 4/30/69.

The shock crossmember has a few tackwelds but is spotweld in place... it isn’t stitch welded in position.

The scope of the project is to get the Boss back on the road, do it as “correctly” as possible, and not do things that would be detrimental to a full restoration at a later date. 

This phase is to cover any exposed bare metal under the car, from the back up to the firewall, and with a factory look (slop grey).  There is some rust spots and I’ll tackle those when the Boss is rolling again and prior to exterior paint.

I have a few questions for sure.  Was the whole undercar painted slop grey up to the firewall and between the rockers?  I’m not entirely certain, but some areas covered with sound deadened were on bare metal... is this poor workmanship or planned from the factory?  It looks like some areas of the plated frame rails are also without paint or epoxy.

[J_Speegle]

9F02G186574 was built in 4/30/69.

Only six days from the build date on mine. There are a couple of picture threads with pictures of my findings to document what I found on mine.

The shock crossmember has a few tackwelds but is spotweld in place... it isn't stitch welded in position.

Likely best the discussion be saved for another thread so that we don't get to far off the focus

  Was the whole undercar painted slop grey up to the firewall and between the rockers?  I'm not entirely certain, but some areas covered with sound deadened were on bare metal... is this poor workmanship or planned from the factory?  It looks like some areas of the plated frame rails are also without paint or epoxy.

Did you view the article in the Library titled "- Undercarriage - Finishes and Sealer Guide for 1969 Dearborn Built Mustangs & Shelby's "

Found that removal of sound deadener can take the layer of paint with it when it comes off depending on how its removed. Other times rust gets under it and removes/destroys the paint layer that way. On original cars the undercarriage paint/primer application normally stooped before the spray got to the rear frame rail but unfortunately this normally resulted in rusting after a time even to the galvanized rear cross member or the frame rails. There can be shadows and thin spots depending on the condition of the spray head in that area. Mine has a number of areas where the frame galvanizing looks like new with all the somewhat fresh looking spot welds and such due to a thin coat or a spray head plugging up for a second or two. Because this is so difficult to reproduce most restorers simply paint edge to edge

Guess I should post some addition pictures of the car (focusing on the sections that have not been redone) and post them in the Unrestored Picture Thread of the site.

Don't know if you have already seen this thread but its more about suspension and what I found related to that subject.

http://www.concoursmustang.com/forum/index.php?topic=6536.0

[Aussie_Boss302]

Mate, that Library is an amazing resource... I feel stupid for not thoroughly exploring the forum before posting my questions.

[J_Speegle]

Mate, that Library is an amazing resource... I feel stupid for not thoroughly exploring the forum before posting my questions.

No problem - there is allot of stuff on the site to discover and read. Sometimes members just need a little help to find it.