To paint or not to paint the underside

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rmchrgr

Skate And Destroy
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Stamford, CT
Soooo, my Duster is in pieces and has not run for almost 7 years. Until this last summer, it was in non-climate controlled storage for the previous 4 years. It's home now and I am beginning the process of putting it back together. I pretty much have all the mechanical pieces that I need on hand so that part just a matter of making the time to complete the individual jobs. My hope is that I can work on it regularly over the winter and have it ready sometime in the spring/early summer.

With most everything stripped off, it's easy to see how crusty it is. Having it sit uncovered in a non-climate controlled garage took it's toll, there is a good amount of surface rust. And to be honest, I've never liked working underneath this car. The undercoating scrapes your hands, there's tons of grime, it's just nasty. The engine bay has seen better days as well. the paint is discolored and oxidized, there's extra holes, chemical splatters and lots of grime.

Cleaning up and painting the underside would make it way more pleasant to work on. The engine bay would really benefit from a fresh paint job. If I'm gonna do these two things, now would be the time.

Believe I have a few options. Number one, I could strip the underside myself with a torch and scraper/wire wheel. That's tedious and messy and I doubt I'd be able to get every nook and cranny as clean as I'd like. It's cheap though and I could do it while the car is on the lift.

Number two, there is a place relatively near me that does a lot of old car media blasting. They would make quick work of the job and it would likely be cleaner than I could ever get it and keep my shop clean too. Drawbacks would be a higher cost and the difficulty of transporting the car on a dolly of some sort. Neither of those things are a deal breaker by any stretch.

The problem(s) with the latter method is that I would probably need to remove everything from the chassis. Not a huge deal, it's mostly there already but I'd have to take off the bumpers and whatever is left in the engine bay so I would be adding a little extra work on the back end to put that all back on.

I also keep looking at the ancient frame connectors and wondering if I should cut them out and get the ones from USCT. I used those recently in my '68 Coronet, nice pieces. That would be a big job in and of itself though. I can weld new ones in myself but I don't have a rotisserie so it would all be overhead which increases the degree of difficulty. It would help to get things cleaner for sure, can't really get at places the connectors are covering up. They're only 2x3 tubing so it wouldn't be a total loss.

Last part about media blasting is how far to go. Not sure how well things can be taped off to prevent damaging the paint on the body. I definitely don't want to paint the entire car, too much money and time, I'd never get the damn thing done. But, there is no paint left on the undersides of the rockers so it would be good to re-do those areas to prevent any further oxidation.

The exterior paint is definitely not perfect. It's been repainted in spots. Seems like it could have been in a minor fender bender or two. I see a repair on the bottom of the passenger door that I hadn't noticed before and some paint drips in the engine bay. It's a 100% solid car though just needs some cosmetic love. But again, I don't want to get involved with painting the entire car, it will never get done.

Also, I'm not sure what to use underneath if it gets stripped. Spray bomb? Real body paint? Truck bed coating? I really don't know. Obviously the engine bay would be EV2 body paint but from what I know painting an engine bay can be a little more forgiving than a full body job. Either way I have a friend who is an ace body man who could do it so I'm covered on that end.

So do I go for it and clean it up or leave the ugly on and just get it running? Appreciate everyone's thoughts and insights.
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Set it outside during a deep freeze, then put it on the lift and use a needle scaler to remove the old undercoat. Comes off easier this way than melting/scraping. Also tends to flake off more, leaving less residue. You can do the final cleanup with chemicals and a torch.

I wouldn't blast - you'll have sand in the rockers and every blind hole for the rest of history. It can be done well, and done right, but is not something to have done casually IMO.

What you do after depends on what your goals are. Daily driver? Undercoat it, truck bed line, something. Occasional driver that will get wrenched on more than anything? Just paint it and let it ride. It'll get dirty, but will be less of a challenge to clean off after. If a daily, you'll want more protection from rust and chemical attacks. If you plan to never drive it in bad weather, less need for the additional sealing.

Just my $.02 - do what you think fits your goals and desires best. If it were me, I know I'd turn the underside restoration into too big of a project on it's own, and so I think I'd just focus on the engine bay by doing some hand sanding/polishing, and using rust converters here 'n there to clean up ugly spots prior to re-applying paint or spray-on asphalt undercoat. That way it stays a manageable project and will help speed things along faster. But that's just me! I don't build restorations...
 
Test a small area with oven cleaner. Halifaxhops swears by it. I havent tried it myself yet but will if oppurtunity arises.
 
I wasnt sure what to do with 69 but needed to protect the new metal without sinking a fortune into it. I ended up rolling/brushing on Armor Coat semigloss.(owned by Rustoleum I believe).
But I looked into a few different options. I bought some paintable undercoat kit, I'll get pics in a bit.
Sandblasting could snowball quick and it would be EVERYWHERE. I bet shop wouldnt guarantee not hurting paint job. Would you consider just coating/painting over top of what's there?
 
If I had a lift, Vixen would be painted and spotless underneath. What's that tell you?
 
dustless wet sand blasting sucks / my friend had a car done/as mentioned you have sand residue// I just became aware of a guy that does this with in 50 miles of me



 
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I've always painted and tidied mine up nicely.But i wonder if undercoating
protects them better and is quieter.Might take that route if there is another
build in me.
 
IMHO.....If there's no rot under the coating, I'd just leave it unless you want to show off the underneath. It's done a great job for 50 years.

EDIT: If you decide to strip it, be mindful of the fact that there MAY be an asbestos component (get it tested). They put that **** in everything back then.
 
My OEM undercoat has protected my dart for 54 years. Leave the undercoat on that is intact. Clean and replace the rest.

Love dry ice blasting!
 
Thanks for the replies so far. Frankly, I detest the undercoating and would like it gone. It sucks for the reasons I stated in the first post. Yes it's done it's job for 50 years but it's normal service life is long over and seems like it's only purpose at this point is to hold dirt and grease. Car is a street machine/couple-times-a-year drag car so it does not get driven during the winter months or over dirt roads. I'm also a bit of a weight saver and getting rid of the undercoating will save a couple pounds which makes me happy. I've had someone tell me they got rid of as much as 50 lbs. but I'm not sure I buy that.

I removed some undercoating from a small area on my Coronet, it goes relatively quick with the torch but I feel like you can't get things as clean as you'd be able to with some sort of blasting process.

Looked around for a local dry ice blasting service but no luck yet.

A needle scaler is also a good idea.

Taking the car to a blasting place seems like it would be worthwhile even if it's only because doing it myself on the lift will be huge mess. It would also be much quicker. Yeah, the whole sand-in-the-rockers thing is a bummer but perhaps if you prep well enough it can be minimized. I'd only be doing the bottom and engine bay so maybe that could also help to keep that situation in check somewhat.

Doing it at home I'd clearly want to have some heavy plastic sheeting to go around the entire perimeter of the chassis and for the floor. I have one of those goofy Tyvek paper haz-mat/paint suits with a hood somewhere to protect myself from all the dirty crap flying everywhere.

The whole DIY process does not seem all that appealing to me though.
 
Most media blasting doesn’t remove undercoating, the media bounces off. It removes the loose stuff only and 80% remains.

the best & quickest way is a heater pressure washer. It leaves the surface clean and nice no residue. Spray with gas to help loosen first.
 
Thanks for the replies so far. Frankly, I detest the undercoating and would like it gone. It sucks for the reasons I stated in the first post. Yes it's done it's job for 50 years but it's normal service life is long over and seems like it's only purpose at this point is to hold dirt and grease. Car is a street machine/couple-times-a-year drag car so it does not get driven during the winter months or over dirt roads. I'm also a bit of a weight saver and getting rid of the undercoating will save a couple pounds which makes me happy. I've had someone tell me they got rid of as much as 50 lbs. but I'm not sure I buy that.

I removed some undercoating from a small area on my Coronet, it goes relatively quick with the torch but I feel like you can't get things as clean as you'd be able to with some sort of blasting process.

Looked around for a local dry ice blasting service but no luck yet.

A needle scaler is also a good idea.

Taking the car to a blasting place seems like it would be worthwhile even if it's only because doing it myself on the lift will be huge mess. It would also be much quicker. Yeah, the whole sand-in-the-rockers thing is a bummer but perhaps if you prep well enough it can be minimized. I'd only be doing the bottom and engine bay so maybe that could also help to keep that situation in check somewhat.

Doing it at home I'd clearly want to have some heavy plastic sheeting to go around the entire perimeter of the chassis and for the floor. I have one of those goofy Tyvek paper haz-mat/paint suits with a hood somewhere to protect myself from all the dirty crap flying everywhere.

The whole DIY process does not seem all that appealing to me though.
It weighs a good bit too, so there's THAT.
 
I posted this youtube video I made a couple of years ago. I used "Sprayable Goo Gone Gell" to remove the undercoating on my 65 Barracuda. Spray it on...(saturate) let it sit overnight and scrape it off. video 1588295171 Undercoating - YouTube I did the whole underside of my car, then painted it.
Norm




Soooo, my Duster is in pieces and has not run for almost 7 years. Until this last summer, it was in non-climate controlled storage for the previous 4 years. It's home now and I am beginning the process of putting it back together. I pretty much have all the mechanical pieces that I need on hand so that part just a matter of making the time to complete the individual jobs. My hope is that I can work on it regularly over the winter and have it ready sometime in the spring/early summer.

With most everything stripped off, it's easy to see how crusty it is. Having it sit uncovered in a non-climate controlled garage took it's toll, there is a good amount of surface rust. And to be honest, I've never liked working underneath this car. The undercoating scrapes your hands, there's tons of grime, it's just nasty. The engine bay has seen better days as well. the paint is discolored and oxidized, there's extra holes, chemical splatters and lots of grime.

Cleaning up and painting the underside would make it way more pleasant to work on. The engine bay would really benefit from a fresh paint job. If I'm gonna do these two things, now would be the time.

Believe I have a few options. Number one, I could strip the underside myself with a torch and scraper/wire wheel. That's tedious and messy and I doubt I'd be able to get every nook and cranny as clean as I'd like. It's cheap though and I could do it while the car is on the lift.

Number two, there is a place relatively near me that does a lot of old car media blasting. They would make quick work of the job and it would likely be cleaner than I could ever get it and keep my shop clean too. Drawbacks would be a higher cost and the difficulty of transporting the car on a dolly of some sort. Neither of those things are a deal breaker by any stretch.

The problem(s) with the latter method is that I would probably need to remove everything from the chassis. Not a huge deal, it's mostly there already but I'd have to take off the bumpers and whatever is left in the engine bay so I would be adding a little extra work on the back end to put that all back on.

I also keep looking at the ancient frame connectors and wondering if I should cut them out and get the ones from USCT. I used those recently in my '68 Coronet, nice pieces. That would be a big job in and of itself though. I can weld new ones in myself but I don't have a rotisserie so it would all be overhead which increases the degree of difficulty. It would help to get things cleaner for sure, can't really get at places the connectors are covering up. They're only 2x3 tubing so it wouldn't be a total loss.

Last part about media blasting is how far to go. Not sure how well things can be taped off to prevent damaging the paint on the body. I definitely don't want to paint the entire car, too much money and time, I'd never get the damn thing done. But, there is no paint left on the undersides of the rockers so it would be good to re-do those areas to prevent any further oxidation.

The exterior paint is definitely not perfect. It's been repainted in spots. Seems like it could have been in a minor fender bender or two. I see a repair on the bottom of the passenger door that I hadn't noticed before and some paint drips in the engine bay. It's a 100% solid car though just needs some cosmetic love. But again, I don't want to get involved with painting the entire car, it will never get done.

Also, I'm not sure what to use underneath if it gets stripped. Spray bomb? Real body paint? Truck bed coating? I really don't know. Obviously the engine bay would be EV2 body paint but from what I know painting an engine bay can be a little more forgiving than a full body job. Either way I have a friend who is an ace body man who could do it so I'm covered on that end.

So do I go for it and clean it up or leave the ugly on and just get it running? Appreciate everyone's thoughts and insights.
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A neighbour’s 69 dart. Original owner. He redid it a few years ago
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Well, I started on the undercoating just to see what it would be like. As predicted, it sucks. My torch has been out of acetylene and I never exchanged the tank so I had the idea to use a wallpaper steamer just to try it out. It kind of worked but the torch works better, the direct flame is more concentrated which helps the coating come off in longer strips. Some of this crap is on about an inch thick and rock solid, no way a steamer is going to make a dent in it. This pile is about an hour of work.
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This is also going to be a very tedious, multi-step process. Getting the undercoating off is only the beginning because getting all the little remnants removed and then getting the metal cleaned and prepped is going to take at least as long. I don't know if I want to put so much of my time into something like this.

Pretty certain my car was undercoated from the factory. I've read that line workers would use cardboard cutouts around the front suspension to keep the new parts from getting coated and it definitely looks that way. I've also read that the factory material was harder than what dealers would put on. That's also true for me, again some of this stuff is petrified pretty good.

It's hard to tell but it looks like there was little to no primer on the bare metal. There's overspray on the torsion bar cross member but that about as far as it goes, no evidence of body color beyond that. BTW, I did not remove anything from the lower firewall area above the floor pinch. That's been like that since I got the car 10 years ago and probably looked like that in 1971.
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If I don't take it somewhere to get blasted I might invest in a rotisserie for this job. Doing it with a lift is 100x easier than on my back but it's still not great. I could have a mobile media blasting service come and do it in my driveway which might be the best of all my options. That way I don't have to transport the body and leave it somewhere, I just roll it out and push it back in. It would also aid in doing some plumbing and whatever other under chassis stuff I have to do

Yeah, it's a huge expense for something that does not get used often but it might be worthwhile in the long run. I have at least one (non-Mopar) future project that will benefit from having it around. Could also rent it out to local guys who might need it.

I'll update when I figure out the best plan of attack.
 
You can smooth over your rough undercoating with 36 grit on a DA sander. Patch in and texture missing undercoating areas with Duroglas waterproof body filler.

Then you can repaint the whole underbody of the car, undercoating and all. Nothing wrong with leaving the undercoating on there, will look factory when done properly.

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We just did it this way on mine...
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My Challenger is painted on the bottom. Looks nice and I feel it protect the bottom just as well as undercoating without all the mess. The draw back is, I drive my car as much as I can and you hear the rocks hit the bottom and, it gets dirty. Call me anal but I clean the bottom 1 or 2 times a year...too much I know...lol

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i own a media blast company and have done tons of floor pans. To dispel some myths first thing. media takes off undercoating no problem. if you are using your 2hp shop compressor and your $79 harbor freight pot...maybe not. scraping some of it first does make the job faster but i can do any floor in an hour-ish. dry ice may or may not take off rust and the cost is probably 4-6x that of dry media. wet blasting is shite on cars. it just leaves mud in places you cant get to and it 100% does nothing more than dry does do other than reducing dust. i own two wet set ups for brick and concrete....not cars.

in my opinion your best option is to have a portable guy come and blast the underside in your driveway.
 
Has anyone ever attempted to use a flooring adhesive remover? It did a good job on my linoleum adhesive about 10 years ago but I never thought to try it on something like undercoating.

The smell was awful so I wouldn't doubt it if the formula has changed since then to make it weaker.

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