Cowl seam sealers

[Beekeeper]

Helping a friend with some rust repairs on his 70 Charger RT before turning my full attention to my 70 Challenger. I am replacing his upper cowl with a new AMD one but I'm wondering how necessary the seam sealer is in this area. It looks to me that any water would simply drain onto the lower cowl and away so is sealer even needed or does it also help in noise reduction? I checked other posts and didn't see many specific product recommendations.

Going to mig it on rather than spot or should we invest in a spot welder for this task. This seems like one of the few areas with easy to reach overlapping joints. Want a nice clean look but it's not going to be a concours show car. My thought was to drill holes in the new panel, clamp, and mig the holes up. I was careful in removing the old one so there is no holes in the lower flanges. Any other ideas welcome. My first big job like this.

As far as sealer, is there a type or technique that allows me to mig weld while it is setting up?

Appreciate any opinions as I move forward. I have to do this job on my Challenger so I really want to learn as much on this as I can.

[AARTA340]

I am nearing the same spot in your progress so will be watching this one as well. I seen the following on Eastwood. Not sure how good it works, but something to take a look at. CODY mentioned in another thread that mig was fine for panel replacement, he was fortunate to have access to a "nice' spot welder.

here is the Eastwood link, maybe we can get some pro's t critique the attachment.   

http://www.eastwood.com/mig-spot-weld-kit-eastwood.html

[Beekeeper]

That's a pretty cool attachment! The video makes it look easy. My Miller unit has snap on nozzles rather than screw on but it looks like the idea is to just get the distance right. I suppose you'd play with wire size and amperage, wire speed, and time on trigger until you find the right balance to create that look. What I've seen done and been able to duplicate easy enough is to just drill a 1/4" hole in the top metal, clamp it down to solid metal underneath with no hole, then just fill the hole with wire which is fairly fast. Then I just knock down the high spot if there is one. With the solid backing, its very easy and forgiving for a newbie welder like me.

I found a product called Lord Fusor 112b which is a "weld through sealant" that also bonds metal. Watched a video on it but they were spot welding rather than mig. I'm thinking of trying it. The 112b is a slow dry sealant which they recommend for large items like this which need more work time.

I've used this brand before for fiberglass and was really happy with it. Anyone try it on sheet metal?

[jimynick]

When we replaced my cowl and firewall, we combo bonded and spot welded it together before installing them onto the car. Without the use of a spot welder, I'd bond it with left-open mig spots to be put in. The story is that the bonding adhesive is amenable to welding while still liquid, but prone to exploding if you try it once hardened. Keep firmly in mind that these cars WILL rot anywhere where two pieces of metal are put together and leaving the seam between the cowl and firewall open, is asking for trouble down the road.  Just my 

[Beekeeper]

Yeah I read that too in a couple other posts. Not sure if the Lord Fusor is any different. They advertise it as weld through but their own video shows it being done wet. I plan to use the slower drying one to give me more time just to be safe. I think you're right about the sealer being needed to keep future rust out. In fact, maybe I should smear sealer into all the crevices after I'm done as added insurance before painting.

Anyone have any thoughts on preparing the top on the lower cowl while it's open? It's not too bad. Just light surface rust. I was going to clean it really good and was considering some sort of rust seal type paint to give it protection since it will never be open again.

[jimynick]

Yeah, clean it right, prep and degrease and paint with a good quality rust paint- Rustoleum, POR15, etc. over an epoxy primer. Then, if you're not bonding it, I'd lay out where I was going to put my mig spots and use a whizzy wheel to bare them carefully for welding. I've considered trying to seal the cowl in it's interior to the firewall, but you'd need arms about 1.5" around, 3 ft long and that were made of rubber to do it all, so I only did where I could reach into. 

[redo1973]

I did a new cowel and firewall.  I scuffed both panels and put an epoxy primer and a flat black.  I'm a novice welder and used a mig to plug weld the pieces together.  I painted the seals with weld through primer and then applied a spot of seam sealer (standard product) only on the upper firewall to cowel area where the water drains and then in the engine bay.  I left the windshield area with only the paint coatings.  I clamped everything and then began welding.  BEWARE - you will get blue flames from the fumes and small ignition of the solid surface.  I had an air hose near by.  This made the process clumsy.  I had to then dress all the welds once it had dried and set for a time.  A little nerve racking doing by myself.  It's not that I would recommend it but it was the best I found at the time.  The idea of the "exploding" adhesive gave me more concern. I plan on putting black seam sealer around the inside of entire cowel by hand.  I'm guessing this is for water and air.  I don't know how water would get up under the cowel at the windshield but I could see an airflow and whistling potential.

[Beekeeper]

Nice work redo! I finished mine last weekend. I did it much as you did and I'm really happy with it. Tried posting pics but I finally gave up trying to resize them smaller. Must be because I'm using iPad for pics.

I used the kit of rust seal by KBS and it came out nice. Just followed their instructions to the letter.

AMD cowl top fit like a glove. It took me an hour to do little fitting stuff and test clamping. It cost more but was worth it!

On the sealer, I tried Lord Fusor 112b because they advertise it as a weld through product. It did all my plug welds before it set up and had no exploding product issues described by others using different brands. Fully cures in 8 hours. Next day, I found two holes I forgot to plug weld. Hit it with the welder and it welded up perfect. Again, no explosion issues even when dry.

[redo1973]

Congrats.  I too had the AMD cowel but a goodmark firewall as I had planned on cutting it up and piecing it into the existing structure.  I think that the goodmark panel was a little off and would have preferred an AMD panel had I known that I would replace it as I did.  I was able to tweak the misses for alignment so no one should notice it.  I also replaced the hex nuts with the OEM "square" nuts and pulled the brake line tabs from my OEM panel and reinstalled on the goodmark panel to simulate an "original" panel.