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which seam sealer??? HELP

I have a 67 Chevelle I am working on. Lots of new metal. Currently I am about ready to epoxy the underside of the floor and trunk pan as
well as the wheel tubs. I plan to shoot SPI epoxy, seam seal, then shoot Upol Raptor Liner over it all.

My question is which seam sealer should I use? 1K or 2K, brand, etc??

I have never done this and I want it to come out nice, not trying to match original factory ways either...

There are so many brands and types to choose from. I need a quality seam sealer that is fairly forgiving for a first timer....

Also when sealing how do you seal say a panel to panel where the gap is at the end of both. My trunk drop off and lower qtr panel flange
is spot welded but both of these end basically parallel to each other so to speak.
Hope you don't mind me hijacking but it's relevant and it makes sense rather than starting a new thread.

Any thoughts on the Eastwood seam sealers? I have read good things about them and they are a bit more reasonably priced.

Regarding the use of 2k products vs 1k, is the crack and pull away comment based upon experience or something you read? I only ask because I have read that same thing in a lot of places yet all of the name brands including 3M and Lord insist their 1k products don't shrink or crack.

Some of what I will be sealing is on the under side of my floor pan so I really cant afford cracking. The point is to seal the seams/overlapping panels that the factory didn't so I can prevent the seam rust I am repairing.

Last question, will SPI epoxy work over any of the seam sealers mentioned including Eastwood.



Trying to be the best me, I can be
1k will always shrink somewhat as the solvents in it evaporate. How much is usually dependant on how thickly it's applied. It is nowhere near as tough as 2 part epoxy based seam sealer either. 2 part epoxy type seam sealer is so superior to 1 part that it is not even comparable. Cures in 10-15 minutes compared to sometimes days for conventional seam sealer. And yes my opinion is based on experience, 25+ years of it. This forum is somewhat different than most as most of the frequent posters are real profesional's, who give advice based on experience not repeating something they read on another forum.

As for Eastwood branded stuff, I would stay away. Use Profesional products intended for use by Pro's. Lord Fusor, Evercoat, SEM all make good 2 part seam sealers. Yes you can spray it over any seam sealer. 2 part type seam sealer can go directly over bare metal. 1 part needs to be primed. If not it will lose adhesion fairly quickly. What would be better is to epoxy any bare metal then use the 2 part on your seams and re-prime after that. Will make your seam sealer that much more bullet proof.
I would not use Eastwood anything. Be careful that you don’t trap moisture by sealing areas the factory did not seal. If you trap moisture it will rust for sure...
My big issue at this point is along with the cost of the 2k sealers those damn applicator guns are so overpriced. I mean, $100 for a caulking gun...

Then I came across this gun. $38!! 81pikEGfZoL._SL1500_.jpg

I'm thinking this with some of the 3M 2k heavy body sealer, 08308, for the underside and some 3m brushable for the inside. It seems to me that the regular 2k stuff that is self-leveling wouldn't be the way to go on the underside. If I put it on too thick it might drip.

Any thoughts on the SEM sealers? They have a 2k heavy body sealer I could use for the external stuff and they have some reasonably priced 1k stuff I would use inside.

Whats the diff between the heavy body stuff and the regular? Is it much harder to work with? Is it better for areas that require a thick application?
I've tried the two part SEM and Norton, both in self leveling version, and found the Norton 97121 to be a smoother finish. The SEM seemed more of a pain to get it to flow out nicely..

Never having used these products before I'm making assumption about the self-leveling that maybe I shouldn't. Are they suitable for vertical seams or horizontal seams that are upside down like on a floor pan? I'm assuming they may run so I should use a non-self-leveling sealer.
Correct, the self leveling would be too fluid on vertical or upside-down surfaces. My post above was more to show I experienced a difference between brands in how the sealer went on...
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LOL. I gathered that and that is good info for my future reference. Thanks. I was just looking for confirmation on my assumptions, which you have provide. Thanks for that as well.

What are your preferred sealers when not needed something self-leveling? What do you like to use under your floor pans?
If you are planning to seam seal your floor pan pinch welds from below you will trap moisture and actually cause rust. Seal your floors from the top and leave the bottom open to allow moisture to drain....

Do the 2k seal sealers need to be painted over or can I just leave them raw? The one I bought is black and so is my epoxy. Unless there is a reason to I'm not going to waste time or money painting it.

Don, I agree, but there are certain seams or overlapping panels underneath that once sealed do not have another entry point for moisture to get in. For example the other side of the seam is inside and the inside is sealed. I don't know maybe I'm being my typical OCD self. I know moisture will probably find a way. It's what it does. I'm under no illusions that rust will creep back and become a problem years from now. This is a unibody car and there are a tremendous amount of seams and overlapping panels under the car. I'm just trying to slow the process. For instance on the frame rails I was intending to seam seal the outer seam. Then I was going to spray the inside with Eastwood's internal frame coating. After that I am going to do an annual treatment with a wax based coating such as fluid film. Again, just trying to slow the process. I have two cars so this one probably won't get driven much in the foul weather. That should help as well.
Unless you can somehow magically hermetically seal your seams moisture will accumulate with each cycle of heating and cooling. It is important that you leave a path for the accumulated moisture to drain.

Condensation. Excellent point. Up here in the North East we get tons of it in the spring and fall. Point taken.

BTW any thoughts on my top coating seam sealer question? I have a few external spots that will have exposed welded seams. grinding them smooth will be a bitch not to mention a waste of time as they are not visible. I just want to rough them up and coat them with SPI followed by seam sealer to cover any pin holes.

Thanks again.
For anyone else looking into this I got my generic gun(pictured in a prev post). $38 from Prime. Comes with a bunch of adapters for different brand cartridges. Pretty substantial, well made gun. Made in England. Definitely a reasonable alternative to the $100 brand name guns.

Also got me some 3m Heavy Body sealer. 200ml. Fits the gun perfectly. Damn is that a small tube. Ordered a second one last night plus some extra tips. $36 seems like a lot for such small tube, but I'm sure it's quality stuff. Took it out of the plastic wrap and man what an odor. Of course I love the smell of body shop products o_O

Does this stuff HAVE to be painted over or can I leave it?

If I prime my dressed welds how soon can I apply the seam sealer? Can I put one wet coat down, wait an hour, lay down the seam sealer and once that skins lay down a second coat of primer?