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Technical Exterior vs. interior paint & prep

Discussion in 'The Hokey Ass Message Board' started by Alt, May 7, 2021.

  1. Alt
    Joined: Jul 28, 2017
    Posts: 71

    Alt
    Member
    from Michigan

    Like most things I'm sure I'm overthinking it, but I'm a bit confused about the proper way to prep & finish the interior vs. exterior.

    I recently had the whole car exterior stripped to bare metal. This included jambs, weatherstripping channels, and anything visible from the outside. Anything that was stripped was given 2 coats of epoxy primer to seal the bare metal.

    The interior is currently in a mix of epoxy primer (over repaired areas - floors mainly), original 'undercoating', and some areas of POR15.

    I understand all that goes into finishing and prepping the exterior, but there are two things I can't wrap my head around:

    1. What is the end-goal of the finishes for the interior steel (does it stay in primer forever, get painted same as exterior, get painted differently than exterior, etc)?

    2. Where does the transition from exterior to interior start? Does the exterior 'proper' simply end at the top, bottom, and side edges of the body panels, and anything from that point wrapping to the other side is NOT finished in the same way?

    Thanks in advance for any help or advice.

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  2. clem
    Joined: Dec 20, 2006
    Posts: 3,406

    clem
    Member

    My opinion:
    Others will have differing views........
    Interior should be prepared the same, ( whether that be bead-blasted or sanded, dipped or something else), then primed and finish coat.
    Where interior is not covered by upholstery, it should be finished to the same standard as exterior.
    Where interior is covered by upholstery/carpet etc, paint preparation obviously doesn’t need to be perfect and top coat of paint won’t need to be buffed, or cleared over or whatever system you use, just not left in primer.
     
    Last edited: May 7, 2021
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  3. clem
    Joined: Dec 20, 2006
    Posts: 3,406

    clem
    Member

    as regards paint finish, - where the upholstery or carpet or hood lining takes over..........
    meaning that door jambs etc are finished as per the exterior.
    Look at a new car to see how it’s done or visit a few more car shows when possible.
     
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  4. Alt
    Joined: Jul 28, 2017
    Posts: 71

    Alt
    Member
    from Michigan

    Thanks. Some good tips and info there.

    I definitely agree about checking out some other cars when I get a chance. It's been a while (so many cancelled shows) and I don't personally know anyone who builds to ask.

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  5. AldeanFan
    Joined: Dec 12, 2014
    Posts: 737

    AldeanFan

    Generally anything that gets painted I would prep the same way.
    I wouldn’t be as picky about finish on an area you can’t see, I don’t cut and polish the floor pan under carpet.

    Any area you can see I would finish the same as the hood or roof.

    You also have to consider your end goals, is this a show car where you would loose points for having paint on an area that would have been only primer from the factory? Is this a show car that needs the underneath of the floor as shiny as the hood? Is this a driver you just want to protect from rusting?

    I have a 40 year old ot driver that I painted the floor pan with rustoleum 20 years ago when I patched it. It’s held up great and is covered with carpet.


    Sent from my iPhone using Tapatalk
     
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  6. BamaMav
    Joined: Jun 19, 2011
    Posts: 4,978

    BamaMav
    Member
    from Berry, AL

    Look at what the factory would have done, do you want to copy that, or step it up a bit? Other than doors, kick panels and rear side panels, much of the interior was left in primer on most cars. They dipped them in primer, and only painted areas that might be showing such as around areas that interior panels covered. Nothing wrong with fogging them with paint instead of leaving them in primer, it will give a lot more protection through the years. And the good thing is you don't have to worry about runs except in those border areas.
     
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  7. Alt
    Joined: Jul 28, 2017
    Posts: 71

    Alt
    Member
    from Michigan

    Goal is a "nice" driver. Don't want to get further down the road and wish I did something that I neglected to do.

    I think you're right on with the prep and paint like the exterior but forego the"finishing touches." Want to keep it protected and feel good about what I've done.

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  8. squirrel
    Joined: Sep 23, 2004
    Posts: 49,279

    squirrel
    Member

    Did you take the car apart? Did you look and see how it was done by the factory? did you take pictures before getting it stripped?

    It's probably too late now...but that's the kind of stuff I pay attention to when I take a car apart, if it's a "virgin". If someone else has already stripped/painted it then the info is already gone.

    But generally, for 1930s-70s cars, the interior of the car that is exposed would be painted a flat interior color, or the gloss exterior color on some models. The parts that get trim over them, were left in primer, although the areas near where paint was exposed, or where the exterior paint was, were generally sprayed with paint, because it's easier/faster than masking it off.

    You might be overthinking it, and you might also not have thought too much about how the car will be treated in the future, vs in the past when it was an old car that no one cared about. Most guys take better care of them now, and don't leave them out in the sun and rain and snow for decades. Maybe you don't need to go crazy with painting everything perfectly, inside and out. Maybe the way it was originally done, is good enough. Or maybe not.

    I had fun with my Chevy II, I wanted it to look like a 1960s race car that's a few years old. So, I had to paint the inside and out with the original type primer, then paint the color as they did at the factory. But much of the primer is still exposed on the interior, since it's a stripped race car. My guess is that very few folks who look at it, see it as I do, but that's ok...I built it for me. You can do the same with your car, do whatever you think is "right".
     
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  9. Tman
    Joined: Mar 2, 2001
    Posts: 34,448

    Tman
    ALLIANCE MEMBER

    Outside colors stop at the weatherstripping. You can carry them inside like the factory if you like. Interior colors start INSIDE the weather stripping.
     
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  10. Alt
    Joined: Jul 28, 2017
    Posts: 71

    Alt
    Member
    from Michigan

    This is a nice simple delineation, thanks.

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  11. Alt
    Joined: Jul 28, 2017
    Posts: 71

    Alt
    Member
    from Michigan

    Unfortunately it was resprayed (poorly) before I got it. The part you said about doing what I think is right is where I think I'm always overthinking - just don't want to make any big mistakes along the way!

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  12. clem
    Joined: Dec 20, 2006
    Posts: 3,406

    clem
    Member

    that’s another reason that the HAMB is so popular, - plenty of experience here !
     
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