Author Topic: Remove the factory undercoat? (Read 15855 times)

mrbill426 · « **on:** June 21, 2009 - 04:38:38 PM »

We have decided to do a rotisserie resto on our 'Cuda and plan to begin it with a full soda blasting of the outer body. The whole underbody (inside the frame rails) has a thick factory undercoat that is pretty much intact and hard as nails. I am hesitant to remove the undercoating since it is in such great shape.

The only real rust under the car is a small rust-through in the floor pan under the driver's left heel, the trunk floor which will be replaced, and of course some rust outside of the frame rails where there is no coating. The rear frame rails are "bad" just in front of the rear spring bushings; those parts will be replaced too.

Has anyone here left the factory undercoat intact and without future problems?

Appreciate everyone's input.

the_engineers · « **Reply #1 on:** June 21, 2009 - 04:49:43 PM »

My car was re-painted 12 years ago and I left the undercoating intact. In hindsight, I wish I had stripped it. I have no idea what's under it, how it looks, what reapirs are needed, etc... WHEN I do strip it, I will probably Rhino-Line the underside. Looks just like undercoating.

Sean · « **Reply #2 on:** June 21, 2009 - 06:05:59 PM »

I just removed the undercoating from the rear wheel houses and frame rails on my Cuda. I used a propane torch and a wooden scraper. It took awhile and got most of the undercoating off. There's still some smears, but it's very minimal and should come off when I blast it.

The metal looked shiney and new after the undercoating was removed. It wasn't until I removed the quarter panel that I realized the outer wheel housisng will have to be replaced anyways.

Here's a pic of what they looked line from the inside when done:

CHUCKS71 · « **Reply #3 on:** June 21, 2009 - 06:26:35 PM »

I removed the undercoating from mine.My friend has a large head propane torch for shrink wrapping boats.Just hit with a little heat and scrape with a putty knife.

73dce · « **Reply #4 on:** June 21, 2009 - 07:49:59 PM »

A heat gun works.

mrbill426 · « **Reply #5 on:** June 21, 2009 - 09:35:22 PM »

I have a heat gun too and am using it to remove the coating from the front inner fender wells, since I will be painting them then re-coating. I just wonder if it would be okay to leave the intact belly coating on where no repairs are needed.

Quote from: 73dce on June 21, 2009 - 07:49:59 PM

A heat gun works.

Bikertrash · « **Reply #6 on:** June 23, 2009 - 10:18:55 AM »

I am just finishing up removing the undercoat from a 70 Gran Coupe that I bought new in "69". Only 26,000 original miles on car but I am going for a roteissary rebuild. Trust me, It is a lot of work, but it is worth it. I found little areas where the undercoat had bubbled and some rust had got underneath. I used a heat gun, made different width scrappers from regular paint scrappers. After all was said and done, I applied a product called "goof-off". It cleaned the remaining small spots and any areas that I missed with scrapper. It now looks like new. The only question I have is how to paint bottom and rails. There was "no" paint on bottom car between rails. Fender wells and outside of frame had paint, but rest was bare.?? Anybody have answers?

mrbill426 · « **Reply #7 on:** June 23, 2009 - 10:56:33 AM »

Thanks, folks, guess I will know more once we turn it belly up.... If I remove the undercoat I was going to spray it with a good primer and re-undercoat it.

dutch · « **Reply #8 on:** June 23, 2009 - 04:42:27 PM »

Quote from: Bikertrash on June 23, 2009 - 10:18:55 AM

I am just finishing up removing the undercoat from a 70 Gran Coupe that I bought new in "69". Only 26,000 original miles on car but I am going for a roteissary rebuild. Trust me, It is a lot of work, but it is worth it. I found little areas where the undercoat had bubbled and some rust had got underneath. I used a heat gun, made different width scrappers from regular paint scrappers. After all was said and done, I applied a product called "goof-off". It cleaned the remaining small spots and any areas that I missed with scrapper. It now looks like new. The only question I have is how to paint bottom and rails. There was "no" paint on bottom car between rails. Fender wells and outside of frame had paint, but rest was bare.?? Anybody have answers?

welcome bikertrash,
You`ve come to the right place , there is lots of great people hanging out here with tons of info too. Introduce yourself and you car in the new intro section. Sounds like a great project you`ve got there

as for the paint... On my car (70cuda) there was some greenish primer underneath the ubc under the entire car.

R/T hedkace · « **Reply #9 on:** June 23, 2009 - 06:07:32 PM »

Seems like you got all the advice you could need, but what's one more idea?

I used aircraft remover.
(Not the healthiest sh!t to say the least)

Also acetone works great if you let it soak in till it evaporates.

And a hell of a lot of scraping

And

quapman · « **Reply #10 on:** June 23, 2009 - 06:30:25 PM »

Were there unwanted airplanes or dirigibles attached to your car???

(Sorry, couldn't resist!

)

R/T hedkace · « **Reply #11 on:** June 23, 2009 - 06:42:44 PM »

Quote from: quapman on June 23, 2009 - 06:30:25 PM

Were there unwanted airplanes or dirigibles attached to your car???

(Sorry, couldn't resist! )

There's one in every crowd ladies and gentleman

And I'm not even gonna lie.....I had to look up "dirigibles"

Sean · « **Reply #12 on:** June 23, 2009 - 09:46:03 PM »

Quote from: quapman on June 23, 2009 - 06:30:25 PM

Were there unwanted airplanes or dirigibles attached to your car???

(Sorry, couldn't resist! )

And where do you put them once removed?

I couldn't resist either!!!

Sean

quapman · « **Reply #13 on:** June 24, 2009 - 06:11:25 AM »

...but seriously, I took off most of the factory undercoat on my T/A many moons ago, and as previously stated, a propane torch and lots of scraping seemed to do the trick. I DID find a few rust spots under there.

sadil340 · « **Reply #14 on:** June 24, 2009 - 06:22:10 AM »

Quote from: mrbill426 on June 21, 2009 - 04:38:38 PM

I am hesitant to remove the undercoating since it is in such great shape.

I removed the original undercoating in my car and there were spots where the coating didn't adhere and rust started. You couldn't tell by looking at it. If you are doing a total resto, I would recommend removing the undercoating. Make sure you take detailed pictures (I took almost 300 of every square inch before starting my rotisserie resto) and you can accurately reproduce where the undercoating was placed.