After no progress in 2022 due to other time commitments I'm ready to get back to my restoration. Most of the rust repair on the middle and rear of the tub is done, but I still have the front end to do. I'm at a crossroads with respect to the cowl-quarter channels.

It's very difficult to see and even more difficult to get good pics but the right side channel has some spots where it has rusted through. Here are some pics:

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But the underside looks great to me. Here's pic of the underside which I cleaned up, rust treated, and epoxy primed several years ago.

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The left side fender-cowl channel is in better shape when looking down into it. Here is a pic:

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I removed most of the seam sealer from the underside but still need to clean it up. As shown in the pic below, there is a spot of rust but it does not look like it has rusted through, so I expect this side to clean up as nicely as the right side.

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So, question #1 is how to deal with these areas. There aren't many threads that deal with their repair but having studied the ones I could find I think I have a good sense of how the two pieces are welded together. It looks like it might be difficult to remove the spot welds in the door area. I believe I can do it but I'm wondering if wire wheeling, treating with metal prep, epoxy priming and then seam sealing might be what's best in this area. Obviously best is always to cut it out and get rid of any sign weakened metal but then getting the panel to look as good after the repair might be a challenge and since this location is kind of buried maybe it's better to leave the nice lines on top and treat it. On the other hand, if it's going to be an issue in the future then I'd rather cut it out and repair now. So this is the conundrum. What say the brain trust?

The top side of the cowl is in nice shape and the channel for the windshield has some pitting but not perforation. I still need to take a wire wheel to the windshield channel. Here are some pics:

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Unrelatedly, one benefit of taking forever to do the rust repair is one gets a chance to see where rust wants to rear its ugly head again. There are 4 spots where I can see some rust on the epoxy primer. Two of them are on the left suspension console where I did the 'weld little rust areas with the mig' techniqe. Here are pics of those:

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And the other two are seams where new metal was welded to old. One is on the rear trunk floor crossmember and the other is below the right rear tail light.

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So, Is this a matter of some rust mixed in with the weld or is that there was still rust behind the area that needs to be dealt with?

P.S. Sorry about the double of one of the pics. The other one is the frunk channel. There are areas of channel that I need to replace but then there are some other spots like the one shown where it is pitted but not rusted through. Also wondering if this should be removed and replaced or treated.

Looking at a few of the photos there is a lack of correct surface prep and the rust pushed through the epoxy primer.
A lot of extra work.
The channel can be treated for the rust and then sealed, I had lots of rust through, I used a cutting disk to remove the rust and mig welded the cuts.

it may help to get one of the small hand held sand blasters and use some glass bead, or black beauty....underneath to remove all the non metal sealer and filler under there, then into the crack.

Also on the areas that have started to rust again...blast them clean and prep the metal properly...then paint again.

rich

I use this for rust removal and surface prep, creates a great key.

https://wurthtool.com/products/dbs-3600-bru...LwaAorqEALw_wcB

This is my repair so far of the cowl area.

http://www.914world.com/bbs2/index.php?sho...=349463&hl=

I seriously think this trench where the rubber trim goes into should not be plugged by seam sealer but allowed to drain in the empty void between the door and the fender.

Thanks for the replies. For metal prep I'm degreasing then using POR Metal Prep, letting it dry over night, and then epoxy primer. It appears to have worked very well except in the spots I've pictured. I'll remove the epoxy and get a better look at what happened; cut and redo if necessary.

The big question is what to do about the fender-cowl area. Montreal914's repair looks thorough and nice. In my case I don't see a need to replace the cowl and my quarter isn't rusted through like his was. So it makes me wonder what is the best thing to do here... There was no rust bubbling on top or bottom in this area, it seems to be just in the channel so I'm wondering if treating and epoxying will do the trick and it might never be an issue...

Montreal914 has linked his thread which is excellent. The only other one which is also excellent at showing how the panels connect is here: http://www.914world.com/bbs2/index.php?showtopic=110572. It has links to some others as well. T

Anyplace that has multiple layers of metal probably has some rust and corrosion. It just depends how far down the rabbit hole you want to go.

Agreed, every time I separate two healthy metal piece, rust is present in the interstice.

I too don't want to fix the driver's side cowl as there are no signs of heavy corrosion like my passenger side had.

That being said, the trench for the rubber trim will need some corrosion stopper. I have places a paper towel impregnated with ospho in there but how deep did it really go in between the metal joint is unknown.

Having gone through the hell of fixing the passenger side, I don't plan on dismantling the driver side.

Definitely looking forward hearing others commenting your your very relevant question.

Well, I'm about as far down the rabbit hole as Monreal914 et al (e.g., Brent Brock). But Montreal914's experience and decision to leave the driver's side alone says a lot. I agree, every seam on these cars with healthy metal when separated has some rust in between so a truly rust free car would need to have every seam separated and treated. But the rust in those areas is really a surface rust that I doubt will ever cause problems (if it hasn't already in the past 50 years). This channel where the rubber goes appears to be a different story as some people have bubbling in the area. I don't want to paint the car and have to re-paint it because rust rears its ugly head there, but there appears to have never been rust on the visible parts of the panels anyway so that's where the blast, wire wheel, treat, and epoxy the crevace approach comes in and might be the best course of action here.

Like Montreal 914, I too look forward to hearing what others who've done this repair have to say. Given that there are only a few threads where people have documented this repair it seems that this area may rarely get surgery, which may also be telling...

Mar-Hyde one step rust converter.

Eastwood Rust Converter.

Two votes for rust converter duly noted.

It appears that not all rust converters are equally effective. This guy did some testing:
https://www.youtube.com/watch?v=tu1n1POMg98

Watched that one and some others earlier this morning. Seems that the best ones are phosphoric acid based. I’ve been using POR metal prep (zinc phosphoric acid) and it has worked well except for the spots in my first post.

I’ve replaced the “pointy” sections of the fenders/cowls on both sides of my current project, probably 10-12” back on each side. they were both rusted thru. I think part of the problem is that enough paint doesn’t get down into that channel when paint was applied at the factory. So what I plan to do is flood and clean the trench(s) with phosphoric acid and water, then get por-15 paint down into the trench with the use of Q-tips, followed by a top coat of regular paint as normal when I paint with the gun.


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Thoughts on using a rust converter then welding the seam closed forever?

Rust converter will burn when exposed to welding temperatures. That stuff is a bandaid, cut out the rust, weld in new, cover with primer, 30 year repair, rust converter, how long? Who knows, I coated the battery box with Navel Jelly 30 years ago and I just replaced it.

Our sporting machines have been around for 1/2 century with minimal care. In another 1/2 century will it matter. W will probably be on to the Jetson age.

Rust repair becomes a challenge when paint is part of the equation. Nobody wants to spend $10-20K on a paint job, just to have bubbles appear in the paint, months later. Getting rid of the rust and properly preparing the metal is the only way to mitigate the issue.

Points well taken from both sides.

If it was removed it looks to me like the only way to get to the spot welds on the underside would be a belt sander, which probably also means welding in a new flange once the piece is out (maybe would be needed anyway).

Looking at this pic of a NOS quarter from Montreal914's thread, I've added green dots where the spot welds go through two layers and lines where it looks to me like cuts would be needed. @Montreal914 does this look correct? It looks to me like once the spot welds are removed through the double wall part of the quarter, then cuts could be made inlcuding a cut through the vertical piece that attaches to the top of the door pillar (don't think it would be possible to even see those spot welds (assuming there are some) let alone see them.

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This is what Navel Jelly looks like after 30 years. The cuts are to make it easier to remove.

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It did it’s job but a permanent fix is needed.

I was forced to make this repair, they tell you in body shop school always replace the latch when making a damage repair to a hood, I didn’t, the latch let go and the hood destroyed the cowl.

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The cowl and fender were rotted, the replacement was from a ‘76 which had the radio aerial on the opposite side, hence the difference in the slope of the fender.
I was able to separate the two pieces repair the metal adequately, weld them back in place.

I looked for some of the photos I took, this is the cowl section I used, it was more difficult than most as I needed to save both sections, this is before the new sections were available.

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You can see here that the rust is surface mostly and after some tig work I can even use the drill holes for plug welds.

I found more photos of the repair.

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I cut the fender back in small sections till I get the work space I need.

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Once I have enough working space I remove all signs of rust.

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This piece had to be fashioned to close the gap where rust has been removed.

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If the process takes me a bit of time, I coat the parts in zinc based weld through primer, (it’s easily removed with paint thinner as it doesn’t have binders in the paint), also if I don’t remove it from creases and folds it is great rust protection.

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It takes a fair amount of time but the results are well worth it.

Nice work. In my case I'd be trying to save, repair, and reuse the quarter piece that I'd cut out. On your image below, I've drawn a green ellipse around the vertical part that sits on top of the door post. You appear to have removed a chunk including where it spot welds to the door post. The red line is where I'm thinking I could cut. Then upon re-installation of the quarter section I could butt weld along that seam where I'd made the cut. I find this area a bit abstract to look at so I'm trying to ensure that I understand how this location all goes together (e.g., took me a while to figure out that the back part of the top of the quarter is double layered).

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This is a pretty complex area. From one of your picture my concern is here:

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Where the arrows are pointing the metal is bulging. Why is that? Well that is because there is rust in between the 2 layers there and it is pushing the metal out yet the spot welds keep this together.

So the question is how to go in there.

The green circle you have in mgphoto's picture is near the "upside down "J" (for lack of better description) joint between the inner layer of the fender (refer to the OEM fender picture), and the area in front of the door. That would be a real pain to drill the spot welds there. So your suggestion of the horizontal cut above it and butt weld seems like a possible solution.

Edit: I guess using the narrow belt sander you might be able to reach the spot welds but you will have to grind the two fender layers to get to the spot welds that are bonding to the cowl. I would do the other cuts first, then maybe you will be able to pull out the fender and rip at the cowl. It will be bad anyway and you will need to repair it. The fender might not be too bad. The weakest link will let go first. So is there a gain to want to use the belt sander? In the end it will damage pretty badly that area.

It was very confusing to me until I began pulling the onion apart.
I believe the section you are pointing to is actually attached to the fender and eventually spot welded to the door upright. I removed the entire rear third of the front fender to repair the door attachment.
The section you circled is what you indicated on the NOS part.