[Formula8]

I have searched the archives for days and have memorized the goat's garage article to see what I should be using for materials for my Endura nose. I am pretty much set for fillers but my question is for Primers, bases and clear coats. I have been using PPG for everything so far and would like to stick with PPG for consistency. Anyway, I see that most use a light coat of epoxy primer for a surfacer. I have been using DP for the rest of the car but I am reluctant to use it on the endura at this point. Some say use the DP but with a different hardener from PPG. Base coat appears to be nothing special but some add PPG's flex additive (I know.... it is temporary). Same deal with the clear coat. However, I have found this from PPG and would like to know what you guys think. https://buyat.ppg.com/refinishProduc...9-b7ae615bd6da

I picked up a quart and will probably use it anyhow but maybe I will return it as when I was leaving the store and asking about the clear coat, the owner said, that the clear is going to crack after the flex loses its flexibility. So, I am thinking WTF? What is the point of a $90 quart of primer if the whole mess is going to crack anyway. Is there an additive that will work with primer, base and clear? Or am I overthinking this. Just use the epoxy, flex in the base/clear and keep the mil thickness low.

I don't see why we can't get to the point where we are with engines on this repair. I mean if you have a 455, you know that a Crower 60919, Rhoads lifters, and a set of ported 6x-4's will do the trick in just about any chassis it will fit in. Why can't we ID the fillers, primers and B/C that is necessary for an Endura nose not to crack?

[PaulatFast]

I would avoid the trick of the week primer. Endura's aren't really that flexible. Use the epoxy, avoid 2k and use alittle flex additive in the top coats if it makes you feel better. The only drawback is that the PPG DP epoxy doesn't sand as well as others we have used. We use Southern Polyurethane Epoxy primer, bonds great, stays flexible and sands easily.

[4SLASH6]

I agree that keeping the film builds thin will help. be sure to test fit endura before paint so when the time comes to fit, you will not be stressing any of the bumper while taking up fender gap etc....... when performing final assembly, do not over tighten bumper to fender sides.have found that these bumpers will pinch and flex fenders enough to hairline crack your cured paint either during install or when raising and lowering car unevenly to perform work underneath. lastly,removing any previous cracks and filling them with 3m 2-part "automix" filler will greatly reduce any previous scars from reappearing. I chose not to use additives. then sprayed entire car with dupont advised primer paints, b/c/c/c. been 6 or 7 years now and bumper still appears very nice sans a few of the hairline paint cracks that I am sure I promoted by said examples. good luck, SLASH.....p.s. PAUL, I like your iinput of the southern poly epoxy primer. gonna right that one down.

[paint guy]

In reference to the above PPG product:I believe that flex. high build primer was developed for the collision refinish industry,to be used on late-model vehicles with bumper covers.to my knowledge,bumpers covers are "suspended"from the car,not subject to stress cracking when raised on a lift.I was surprised when a friend of mine raised his 69 on a lift,the endura moved much more than I thought it would,hence the possibility of stress-cracking.I have an endura bumper that has been primed with Sem#39134 Flex.surfacer,took about a 25-30 degree bend before cracking.(I tested it)That material "cobwebs"when sprayed,which leads me to belive that it is either chlorinated rubber or vinyl based(either can be made very flexible).Not saying this is the best way by any means(may not work,no way of knowing until a couple of years have elapsed)just saying it could be another option.Experience is usually the best teacher,sounds like either of the above posters have done this more than once.They are both dead on right about keeping film thickness low( no need to build epoxy up on plastic,no need for corrosion resistance.)Lower film thicknesses will stay more flexible in the long run.If anyone is interested,I would be happy to send a couple of std.steel test panels to anyone finishing endura bumpers on a regular basis,they can then be coated and sent back to me,and I will run a Mandrel bend and gravelometer(chip resistance) test on them and post results here in this forum,in an effort to establish some useful info for future Pontiac restorers.For this to have meaning,we should probably do a comparative test on at least 3-4 different systems.Anyone interested?

[Formula8]

Thanks Paul,Slash and Paint guy. I like the idea of confirming what works and what does not. However, I am thinking some rubber strips of some sort would be a better test material. My bumper near the hood is pretty flexible. That is where most of the problems are with an F-body.

Here is a link to some rubber that is 3/8" thick and about the same durometer of tire rubber. http://www.mcmaster.com/#rubber-sheets/=3wxtcu

[PaulatFast]

I would be happy to spray test panels with the products I have here. I would be interesed in checking the SPI epoxy at different mil thicknesses.

[paint guy]

Paulatfast ,slash,and formula8:If you will P.m. me your addresses,I will mail to you some test panels.Painting consistent rubber strips will also generate some useful info,IMO.After panels are painted and cured,i will check film thicknesses,run a flex test(mandrel bend) and graveometer,to ASTM test specs.After testing,I will post results and mail panels back to you,if you like.It is important that all panels are painted in somewhat the same time frame,then I will age them about 2 weeks before testing.Please let me know how many test panels you need,and don't forget to mark them as to what they are.Thanks to all,I'm sure we will generate some meaningful test data.

[Formula8]

Cool. I'm willing to pop for the some rubber strips. McCaster probably could drop ship to Paul's place and he could work his magic and send them to you for testing. At $90/quart, I really don't want to open up this PPG stuff if I can still return it.

[niceta]

Hello. ran accross this post in a search. Is this test still going on or did it die a slow thread death?. Just interested as it sounded like a great idea and sounded like paintguy was willing to do the leg work. I will be painting a 73 TA bumber in the future and want the best syatem out there. Thanks

[ry57pont]

i can only speak to what i have done (i am not a professional- i painted one car) i took a two day paint class from PPG at a local jobber here in town. i specifically asked about endura. here is the info i got from them. (ppg)

add flex in the primer surfacer
add flex in the sealer
do not add flex in the base, use dx57
add flex in the clear.

here is what i did on my own 70 gto.

i used evercoat poly-flex glazing putty for any big scratchces, gouges
i added flex in the primer surfacer (k36)
i added flex in the sealer (i used shop line jp385, ppg's brand one step above omni)
i did not add anything to the base (DBC)
i added flex to the clear (DCU2042)

after the first year i did some tranny work and jacked the car up from one side, as 4slash6 stated it cracked where the bumper hit the front fender. (really only noticable to me)

other than that i have had no issues, i did not follow PPG's recommendation on adding dx57 to the base because it listed dx57 as a basecoat hardener and i was not to worried because base is generally thin anyway. ppg did say they painted a phone cord(when phones had cords) and after they were able to use the cord without it cracking, but did not say how long it was after painting.

in any case, get your gaps right now, mark your holes, and install after full cure. i dont think any amout of flex will help after a longer period. i may have tried to get my gaps too tight and that was my downfall.

[Formula8]

I only started the post last weekend. Anyway, I have been buried at work but plan to order the rubber strips by the weekend.

RY57, Thanks for the PPG recommendations but it appears you still had your paint crack. I am sure there was some process or product used by the factory as it appears this was not problem until the cars were repainted. Logic would lead one to conclude somewhere along the refinishing process, a proceedure is skipped or a product was not used/or added which is leading to the cracking.

What drives me nuts is my Mazda DD was rear ended and pushed into a Mercedes by an ambulance last year. There is some real minor frame and absorber damage. The rear cover has some depressions from the license plate and some scratches but not one crack in the paint. Same deal with the front cover. Now if I jack up my Firebird, I have to worry about the paint cracking on the bumper??? Something is not making sense here.

[ScottD3]

I am getting ready to redo my front nose on my T/A and would like to see the info also. When I picked my car up a little over a year ago from the painter I took it back and showed him the paint cracked and it looked as if it was bubbeling up. So any info would help for the repaint. Thanks.

[PaulatFast]

My shop address is easily found on my homepage, follow the link in signature.

I can tell you the poly-flex evercoat product does not bond to the endura nearly as well as the Rubber-Seal rs2301 I have been using for years. 3M makes a very good two part flexible repair product as well. The only primer I will let touch endura in my shop is SPI epoxy. Tried, true and proven. Dupont and PPG will tell you whatever you want to hear to sell product. They could care less about hobbiests and resto shops, that's not where their money is coming from. They train their guys to sell their products, whether they are correct or not. I can't tell you how many times I have sat through a Seminar put on by a sales guy giving false information. I cringe when I see guys taking notes!

[niceta]

Originally Posted by Formula8

I only started the post last weekend. Anyway, I have been buried at work but plan to order the rubber strips by the weekend.

My appologies I must have been looking at your join date ...

[rememberfireball#22]

I agree with Paul 100% about the sales tactics of the big paint companys. I went to a seminar one time and the Dupont rep made statement in front of class that it was always better to replace any panel instead of repair, no matter how minor damage was. Can you imagine cutting a factory panel out like a quarter for an couple of hours dent? I never drill out factory welds if I can save panel, but I'm not using anywhere near the materials that I would be using if I replaced panel. If you can repair there is less likelyhood of having to blend conecting panels.

[Formula8]

Paul, are you saying that if the SPI epoxy is used and applied correctly, the BC/CC will not crack in your experience? What are you using for those? If you are not having a cracking problem, then the test is pointless as you have already found a solution that works.

[PaulatFast]

Originally Posted by Formula8

Paul, are you saying that if the SPI epoxy is used and applied correctly, the BC/CC will not crack in your experience? What are you using for those? If you are not having a cracking problem, then the test is pointless as you have already found a solution that works.

I have been saying that for years! However, I'd love to have the testing data for backup. I exclusively use SPI clears. For base, we have switched around abd sprayed many different brands, while I love the Pro-Spray I now use, we have endura's out there with Chroma-base and Nason (Dupont),DBU and Omni (PPG) SPI base, Crossfire and the better line from Martin Senor. The base hasn't made a difference in my experiences. Since I have started stripping the endura's bare, which is extremely important, and repairing the noses with RS 704-5 (I listed the wrong pn in my post above), I have not had the first issue with cracking. I have followed this proceedure for over three years. Barry Kives, owner of SPI Inc. and I have discussed this at length, he uses the same proceedure and has had some of his work hold up for over a dozen years. I think he made a few beleivers at the Co-Vention this year during his Seminar. I know for sure one guy that called me a backyard bodyman for suggesting this method and saying flex agents weren't needed (on another forum) attended and was impressed. Milt Robson's Black Judge Convertable was done by Barry years ago and still looks perfect.

One thing we will need to do is spray enough samples to perform these tests again in about three months, after everything is fully cured. That will be the true results we need.

[paint guy]

P aul,how many variations do you want to test?I have the bare steel panels ready to ship to you,and will get your address from your website(I think I have about 8-10 panels,is that enough?)To simulate full cure,rather than waiting for 3 monthes,my plan was to force cure all the panels at the same time in an oven @120 degrees for about a week or so,then run a controlled bend test and gravelometer test.Really the most accurate way to test(I know this is asking alot)would be to find a junk endura bumper,cut it into similar sections(about 4"x6" or so)and then paint them along with the metal panels I will be sending you.If thats possible,i can also force-cure those and run gravelometer on them,along with adhesion.If not,consistent rubber strips will have to suffice.Since you know you have system that will perform,my objective is to establish what level of flexibilty and/or adhesion is demonstrated by your known system,and can it be acheived by other paint systems.
In reference to an above post stating that a Mazda bumper cover sustained no cracking in a collision,please keep in mind that if the car is a fairly late model,it is quite possibly painted with factory paint,not refinish products available to body shops/restorers.Late model,factory paint is quite likely water-based(flexibilized acrylic or polyurethane dispersion)base-coat,and a melamine type baking clear(or even powder-coat).In any case,products designed to provide superior adhesion to the substate(late model bumper covers are made from different material than a forty year old endura bumper)and are superior in many ways to off the shelf 2K refinish materials to be sold to the masses.

[Formula8]

Ok, I am ordering the rubber strips on Friday. I started to think about it and I am thinking either 3/8" thick or 1/2". I'm looking at one of my durablocks and it is 1/2" thick. Any opinions?

[4SLASH6]

I too sanded my 2 endura's complete by hand and 1 had what I believe was 1 enamel (single stage) repaint. wow, that was some work! my paper would gum up in no time and stick and fly right from my hand. spent a lot of time on it thats for sure. there was a fella north of me who was plastic media blasting these bumpers and heard the results were very good with no damage. friend of mine just sold a very nice 70 judge clone and after a hot day in the sun his paint lifted at the big radious or bend near the center nose towards the top/flat. I mean the lift was almost a perfect circle and did not crack but must have been the size of a small plum!! 1st thing I thought was film builds but now maybe it was the primer type..........