Underbody primer and DP74LF,

Discussion in 'Body Restoration' started by 70moneypit, Aug 13, 2012.

  1. 70moneypit

    70moneypit Veteran Member

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    This is my first post, never had much to contribute but I've been enjoying and learning a great deal from this website and the members here for quite some time. I've been able to save a lot of money and headaches just due to the info found on these forums. There's simply no other place like it on the net for this kind of info.

    Anyway, what motivated me to post was the subject of underbody primers, which I know has been discussed here many times. I have read quite a number of threads on the matter, so i hope I didn't miss any that might have already answered the questions I'm about to ask here.

    Several types of finishes have been discussed to emulate the Fisher Body primer sealer on the bottom of our cars. Although many have touted other brands, such a SPI and DuPont, the PPG epoxy primer (red oxide DP74LF) seems to have favor judging by mentions, plus it's the only one that folks feel proud enough about to actually post images of on their cars. Most of the guys who have used DP74 have had positive things to say about it's cosmetics and durability. It's worth mentioning that at least a few times I have read a post commenting that it's a little "too red" by a few guys, but I wonder if that depends on the year of the car, the lighting, or the weathering their car has endured, or the color of the overspray the bodies received during their final finish paint job. Were earlier cars coated with a more reddish primer?

    Some images posted here and elsewhere did seem to show DP74 that was quite red, while others looked spot on to me, especially judging by the photos of original survivor 1970 model year cars.

    In any case, I decided to use DP74LF on my car, which is a 1970. I plan to clear coat it to get just the right shine, using matted clears now on the market.

    First off, I cleaned the bottom of the car from front to back because it was coated in a rather thick filthy layer of old oil and road grime, most generated by an oil gauge line leak on the block that must have been going on for ages.

    It may have been a blessing, because I was surprised to learn that the oily layer (plus maybe the fact it's a California car) seems to have pretty much protected a very well preserved Norwood underbody red oxide primer for all these years. In fact, it looks nice enough that I'm still trying to decide if I need to do a full respray, or just fix a few places where it's worn off? What do you guys think I should do here? I also should mention I do have one small rust spot to repair.

    I an thinking that sadly, once I start spraying DP74LF I won't be able to stop until the whole floor is covered over since the new finish wont quite perfectly match the old worn finish, which also varies in color depth as you go back to the rear of the car. this is mainly due to a progressively heavier amount of body finish overspray coverage.

    On my car, which was white, this means it starts to make the primer look pink as you get closer to the trunk area.

    Well, getting to my main question. The DP74LF I got looks browner than I first expected when I opened the cans (I got two). It's not too red at all, in fact i had hoped it would be just a shade redder. So did they change the formula up?

    I did a brush out to compare to my car, and I guess it's good it's not any redder than it is. After a great deal of comparison, it's as close to a match for my 1970 as I think is possible to find, in fact even if I'd had it custom matched, I doubt i could get this close.

    Now my second question, I know once i spray this out it's not gonna look exactly the same as a brush out, but in my experience that should only affect the sheen and possibly the darkness level, and not the coloration in relation to red versus brown, am I right or wrong on this?

    I took some images to show you what I am talking about. Please comment if you have any observations or advice for me. Some images were taken in direct sunlight, others in deep shade, some in indirect light,. I tried not to use a flash, that always seems to make colors look off from what you would see under natural lighting.

    These are just shots of the underbody as it looks now. hard as hell to take good images of this area with only inches of room under the car. That's the original black firewall paint and the demark between it and the underbody paint.

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    On my car, there's little to no overspray at the front of the car and along the sides, all that starts near the back sat bolt area and seems to have been caused mostly when they spray body color into the rear wheelwells. I see some restorers add it along the entire side of the car.

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    Here's the two front drain plugs, are these just phosphated? They don't seem to rust. Obviously put in well after the base primer is put on.

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    This area around the centerline transmission hump reinforcement had enough indirect sunlight hitting it that I was able to get what I consider a pretty good shot of some clean, non-faded factory primer in a true color. Most of the other photos I took, couched under the car, were either too dark or to fuzzy to see this amount of detail.

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    This shows a view towards front from near the back, near the rear seat anchors. Here you can start to see the white overspray as it first shows up on the driveshaft tunnel. White paint on the left side was shot across from the left side of the car, and vice versa. This white overspray made the red oxide primer look pink or salmon tan.

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    Here's the rear seat belt bolt anchor support end rubber bumper mount area for the rear end, the paint is nearly pink in color, lots of overspray from the wheelwell paint. MY car was never undercoated, but there was a small patch of some sort of factory undercoating or black sealer applied here around the support seams and on the bottom of the rear seat anchor area, I removed a great deal of it while i was cleaning, but it was a PITA to get off. I just wanted to make sure there was no rust under it, i think I will redo it, what do I use? Will rubber undercoating/truck bed liner spray last long?

    My dual mufflers also go here, will they catch rubber undercoating on fire, hehe?

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    Last edited: Aug 13, 2012
  2. 70moneypit

    70moneypit Veteran Member

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    Okay, now for the DP74UF. Here's my brush out, I let it dry for four days then coated it with a light coat of clear. I was planning to coat the DP74 I spray on the car with matte clear like they use on MB's and Lambo's to get that eggshell sinish, to protect the primer. My factory primer is very shiny in most places where it's new and in good shape, way more so that the DP74 before I cleared it. From past experience, I think spraying it will make it glossier, right? Images seem to bear this our, unless others cleared theirs as well?

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    Now for some comparison shots, under various lighting and in areas where i think the factory primer was still in good condition. judging just by this brush-out, I think the color match is as good as you could get?

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    Well , I guess that's all I have to contribute. Please let me know what you think about my assumptions. I'd like to get some input on my plan before I start spraying.
     
    Last edited: Aug 13, 2012
  3. rydeer

    rydeer Veteran Member

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    I don't know about your primer, But, I wish I could get my underbody that clean!!!!
     
  4. Rich Schmidt

    Rich Schmidt Veteran Member

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    I have found that epoxy primer usually has a gloss that is closest to what you are looking for. The problem I have is in finding epoxy in that color. Its usually black,gray or buff,and most dont recommend tinting. I have found that even in areas that were very well protected like under the headliner and such(no heat there) the color is fairly dark and brown. Our cars were painted in a fog,so a lot of what you see in the color variations is the fine overspray from the paint shop. If you ever poped the spot welds to replace a panel you can see the truest color of the factory primer. From there you can get your correct coloring by overspraying color(like a drop coat) over the correct color primer.
     
  5. earlysecond

    earlysecond Veteran Member

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    WOW, that IS clean. With that said, it looks like you found a good match and the product is top notch. I would spray a couple of med. coats and make sure you can live with the color and the sheen. If not you can topcoat for an exact match in color or sheen.

    I would hesitate to put much of anything on it all, especially if you are going for a concours resto! Original wins points I think.

    Good luck and post up pics. Why did you wait so long to speak up? j/k
     
  6. Rich Schmidt

    Rich Schmidt Veteran Member

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    I couldn't see his pics before.that's a good match. The real secret with concours restorations is to do it so well that even the judges think its a low mile original paint car. I have thought of making that a personal challenge someday. Using real single stage laquer,blending the color and laying out the metallic to look like aged original,flowing the seam sealer with a heat gun to look like it was factory baked ect. Using tea to age paper tags,mixing my own chalk markers to make the colors look browned and aged. Measuring the mil thickness of all the painted surfaces and making them identical to original aged paint(which typicially has shrunk over time). The ultimate forgery.
     
  7. earlysecond

    earlysecond Veteran Member

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    Rich,
    That would be an all out effort of love. . .I have enough trouble putting the effort into getting a nice paintjob done!!
     
  8. CamarosRus

    CamarosRus Veteran Member

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    In a previous thread I recall Ken Smith aka "Boardog" acheiving Norwood Red Oxide with a formulation of SPI's Epoxy ??

    Anybody agree with me
     
  9. 70moneypit

    70moneypit Veteran Member

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    Thanks for the comments, guys. I never get tired of hearing what others have done, or getting advice before I waste money or time messing something up.

    Rydeer, thanks, a couple of hard labor weeks of laying on your back covered in degreaser did the trick. My neck muscles sure grew stronger, hehe. Too bad people over the years didn't know (or care) where to locate floorjacks on our cars, or add muffler hangers for that matter!! For instance, how many of those dang screw holes behind my back seats are supposed to actually be there? None, probably, hehe?

    Rich, I do hope the primer gains some gloss after I spray it, it is certainly ultra-flat just brushed out. I'm just nervous about leaving it bare to the elements, though, so it seems like a matte clear could be used on the new (as well as the old) primer to seal it in and add that little bit more protection, especially UV protection which I have read the epoxy has no barrier for.

    earlysecond, I agree with your suggestions on keeping things original, I hate to redo stuff but frankly this car will never be close to good enough to show in a concours event, although I'd love to say it would, hehe. My goal is just to preserve what's still there (the car deserves that much) and to finish it one day with results that will be nice enough to at least please me. If anyone else makes a nice complement about it then that's icing on the cake.

    BTW, by following the handy link in your signature block I read your entire thread on the rebuild/restoration you are in the process of doing, great work man! I was also happy to see you found a job. I look forward to seeing more updates on your car as you progress, nice job!

    I've spent I don't know how many thousands on mine already, more than it's worth, but it's a labor of love, right? I've found some minor surprises after tearing it down (who doesn't?), but so far nothing bad enough to make me regret spending the money, one pile at a time, hehe.
    .
    CamaroRus, I was hoping you would post here, and tell me what you think about all this. I've read your thoughtful posts on this subject many times with a great deal of interest. I must have missed the thread you referred to, I will see if I cna find it.

    So are you now thinking maybe the SPI epoxy primer would be a better choice? I have no experience either way, I've just read that the SPI epoxy is easily sandable creating a powder residue, that just makes me think it's softer and more porous, i.e. less of an epoxy than those which are hard to sand once fully cured. Heck, I have no idea but I have not yet seen a single posted image of floorpans done in SPI or DuPont products, did I miss them?

    I do think the latest full color Year One catalog shows a lot of shots of the DuPont-finished Dynacorn floorpans ('69) in various sections of the book, and they look real nice, color wise and all. I have also seen several very well done PPG underbody paint jobs here on this forum. A picture is worth a thousand words, especially since everyone has their own opinion about how dark or light or red the finish should look when done.

    I guess I'm just trying to rationalize my choice in product, since I can't really afford to switch over unless you guys think I'm making a major mistake. I need to spray this in the next couple of weeks, to get the car rolling again and ready for the paint shop, and I only want to do this one time, hehe!
     
  10. CamarosRus

    CamarosRus Veteran Member

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    Im on puter at work and all the pictures dont appear......just small red X's...
    Is this an issue with network at my job place???

    Ill try and remember to look when Im home
     

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