Painting underbody grey... am I nuts? - Vintage Mustang Forums
Thread Tools
post #1 of 35 (permalink) Old 09-24-2018, 04:44 AM Thread Starter
Join Date: Apr 2006
Location: Southern California
Posts: 59
Painting underbody grey... am I nuts?

So I have my mustang up on a rotisserie and stripped (by hand... yes it sucked).
I have a lot of grey epoxy primer, how crazy would it be to just paint it with 3 coats of grey epoxy and leave it at that?
It was originally a sloppy black color with some body color overspray and 49 years of grime.

I think it might actually be nice to have a lighter undercarriage when working under the car.
Then again a light color would show more dirt... but it's under the car so does it really matter?
Either way I would put black undercoating in the wheel wells for protection.

I could always buy a bit of black epoxy now just in case I change my mind and respray the black over it during the recoat window (I will likely need the black anyway for the engine compartment)...

I know Ford didn't do it this way, that doesn't really bother me.
I'm just wondering if someone has done the same and can say "don't do it because of X" that I haven't thought of...


69 Mustang Fastback... in pieces since 2009.
steferg is offline  
Sponsored Links
post #2 of 35 (permalink) Old 09-24-2018, 06:55 AM
Senior Member
22GT's Avatar
Join Date: Jun 2009
Location: Southeastern Pennsylvania
Posts: 33,852
The crude black with body color overspray is of course concours correct. No harm will come to your car if you use gray.

Amateur restorer. Well, sometimes I have been paid for it. But not right now.
22GT is offline  
post #3 of 35 (permalink) Old 09-24-2018, 07:41 AM
Senior Member
Mach1 Driver's Avatar
Join Date: Jul 2015
Location: Atlanta
Posts: 580
I got this from BuckeyeDemons build thread on another forum:

Klutch said:
Buckeye, it appears you painted the undercarriage a gloss gray. Is that the way your car came from the factory? It looks great!

I thought the undercarriage was supposed to be a shade of red, but maybe that was just the '70 Mustangs. Likely, I'm just confused.

BuckeyeDemon said:
it depends on what plant the car was built at and what day.

can you find any remnants of original paint on yours? i can't speak for all years and plants, but in general, Dearborn used leftover topcoats (all mixed together) to spray on the undercarriage (from the firewall back). so the color of the mixed paint could vary.

on my original undercarriage you can see the grayish color, along with some of the candyapple red overspray and the black from the pinchwelds.

Original Owner 69 Mach1
Mach1 Driver is offline  
post #4 of 35 (permalink) Old 09-24-2018, 07:49 AM
Senior Member
j persons's Avatar
Join Date: Aug 2010
Location: Natchitoches, LA. at the edge of the swamp
Posts: 4,078
The underside on mine is going to be the same color as the top. I'm also using a gray epoxy primer and thought about just leaving it in primer, but the epoxy primer is not UV resistant. I realize it is on the bottom, but still can be affected by UV at the wheel wells, etc.
vegasloki likes this.


The Fauxstang. Dynacorn 67 fastback. Dart SHP 363, Close ratio Magnum 6 speed, 3.70 Eaton Truetrac in a fabricated full floater 9", SorT coil over suspension. Still in pieces.
'14 SHO with most all the bells and whistles. Stock for now.
F-150 SCab daily driver
j persons is offline  
post #5 of 35 (permalink) Old 09-24-2018, 07:49 AM
Senior Member
Huntingky's Avatar
Join Date: Sep 2011
Location: Central Kentucky
Posts: 3,086
You didn't specify the type of build you are doing: concours, daily or restomod....garage queen or road warrior. If you really plan on using it the primer, although original, is pretty weak solution, painted top coat or some type of undercoating would be best.

Coyote build in 65 GT Fastback in body work and on Facebook @65gtmustang
F150 SCREW Ecoboost as my daily
66 Emberglow Coupe first car,71 Torino GT, 82 Fastback slooooow 6 banger, 71 Boss 351, 85 GT all long gone
Huntingky is offline  
post #6 of 35 (permalink) Old 09-24-2018, 08:28 AM
Senior Member
Join Date: Jan 2006
Location: apopka,florida,usa
Posts: 307
It is a crazy idea.Paint it either red oxide or black.Why would you want to stray from original? A grey primer justs look like you ran out of money to buy paint.A grey underside will reduce your resale value when the day comes.
Israel likes this.
shelby289s is offline  
post #7 of 35 (permalink) Old 09-24-2018, 10:26 AM
Join Date: Jul 2016
Posts: 64
Its your car - use grey if you want to..
Rorin67 and j persons like this.
cliffgrove is offline  
post #8 of 35 (permalink) Old 09-24-2018, 10:42 AM
Just some guy
Supporting Member
GypsyR's Avatar
Join Date: Jun 2001
Location: SC foothills, USA
Posts: 19,158
Mine was red oxide primer underneath. I went with gloss black because that's what I like.
I experimented with some PPG DP40LF epoxy primer by painting an old truck hood with it and then driving it that way for over two years. There was a bit of fade from the sun but it held up very well. (Dirt, tree sap, bird crap, etc.) Unlike some other primers, the epoxy is supposed to be waterproof and mine seemed to be. So if you are using that or an equivalent primer I can't think of any reason not use it. Be aware that oil and transmission leaks sort of "stain" it. IE, it doesn't quite wash all the way off like it would a gloss or semi-gloss paint. The effect isn't that big a deal though.

Last edited by GypsyR; 09-24-2018 at 10:44 AM.
GypsyR is offline  
post #9 of 35 (permalink) Old 09-24-2018, 11:32 AM
Senior Member
69GT350H's Avatar
Join Date: Dec 2015
Location: Miami Florida
Posts: 3,266
Your car, do what you want. Original (Concourse) you'd want the red oxide (early) or batch paint (later) color. I found my color under the rear axle breather tube bolt, then had a quart of epoxy made up to match it. Original looking and durable. I've also seen some painted body color that looks good if the bottom of the car looks nice.

VMF Build Thread - 1969 Shelby GT350 Hertz rebuild Gallery
Used by Hertz for the 1969 "Rent-A-Racer" program at Miami Internation Airport.
69GT350H is online now  
post #10 of 35 (permalink) Old 09-24-2018, 11:35 AM
Senior Member
Join Date: Oct 2006
Location: Queensland, Australia
Posts: 545
Has already mentioned, a grayish paint is factory finish for a lot of Dearborn cars. Visibility seems to be better with a lighter colour.
A friend of mine painted the area up under the dash a gloss white, you can actually see things when looking under the dash.
I know working under my 67, with its grayish batch paint, seems a lot easier than working under my 65, with its black paint.
289vert is online now  
post #11 of 35 (permalink) Old 09-24-2018, 11:35 AM
Senior Member
turbo2256b's Avatar
Join Date: Feb 2013
Location: KY, OH, MI
Posts: 1,747
I used Silver bullet under my Merc years later some rust came through years later and addressed it. this was not a frame off restoration. makes it easy to see working under the car and expected a few places to show rust after time.

Also if dirt, oil, tar, etc needs to be cleaned off some brake clean, or carb cleaner will remove the stuff without removing the paint.
Attached Images
File Type: jpg IMG_0003.jpg (388.5 KB, 12 views)
File Type: jpg IMG_0005.jpg (408.0 KB, 11 views)
Rorin67 and Huntingky like this.

Last edited by turbo2256b; 09-24-2018 at 11:40 AM.
turbo2256b is offline  
post #12 of 35 (permalink) Old 09-24-2018, 05:47 PM
Senior Member
buckeyedemon's Avatar
Join Date: Dec 2007
Location: Cincinnati, OH
Posts: 2,978
if the grey looks like a sandable type of primer (e.g dull/flat grey), then it will look unfinished in my opinion. if it's the glossy (batch) color ford used, then it looks intentional.
Mach1 Driver likes this.

buckeyedemon is offline  
post #13 of 35 (permalink) Old 09-24-2018, 08:35 PM
Senior Member
Tallguy's Avatar
Join Date: Apr 2016
Location: NorCal
Posts: 831
It's just the underside. If you care what people think when they look under your car then paint it what color you think they would like. If you don't care what other people think then paint it whatever color you like for whatever reason.

I do not plan to show my car ever. That said, I suspect 0 people will look under there and if they do I don't care. That also said, mine is black.... And I have Raptor liner in the trunk, wheel wells, etc. The concours guys might like like my car. But it's not concours so I don't care....

66 Convertible. Full restoration in the works
Tallguy is online now  
post #14 of 35 (permalink) Old 09-24-2018, 08:44 PM
Supporting Member
Laurie_S's Avatar
Join Date: Mar 2001
Location: Tucson, Arizona
Posts: 19,437
Mine is striped.
subpar63 and 69GT350H like this.

"I love it when a plan comes together!" -- Hannibal Smith


Murphy, 1968 Coupe - Concours
Trouble, 1968 Fastback - Modified
MiniMe, 1966 Mustang Jr. - For Fun

MCA Gold Card Judge, 67-68 Concours
MCA Gold Card Judge, Modified All Years
MCA National Secretary
Laurie_S is offline  
post #15 of 35 (permalink) Old 09-24-2018, 08:53 PM
Senior Member
ruger's Avatar
Join Date: Feb 2003
Posts: 955
My 69 Dearborn was metallic grey. I scraped from the front to the back and from side to side. All metallic grey with exception of Silver Jade over spray at all edges. I put it right back the way I found it.

God bless.
ruger is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Vintage Mustang Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are Off

For the best viewing experience please update your browser to Google Chrome