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Old 03-19-2021, 05:45 PM
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TheBandit TheBandit is offline
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Join Date: Jan 2006
Location: Ventura County CA
Posts: 4,654
Videos are cool but they take a while to edit and I am still a forum junky, so I'm going to try for a text & photo update to get this thread up to speed.

Subframe Connectors

If you haven't seen the part 1 video of my subframe connector install, there's a lot more info there to complement what I'm going to type here, but since I haven't found the time yet to edit part 2, I'll go ahead show some start to finish photos of the install.

Installing weld-in subframe connectors requires access to the floor pans so I stripped out the interior, revealing rust areas I haven't looked at since around 2004. Way back then I wire wheeled the floor and put a coat of Rustoleum "rust stop" primer over everything. I called Rustoleum at the time and confirmed it could be left as a top coat. Over 15 years later I am not unhappy with how this held, but it's certainly no panacea for rust. Things have gotten a little worse, most likely from time periods I had the car stored outside with water leaking through pretty much every window on the car. The passenger side is the worst, with pin holes and very thin areas right around where he subframe connectors needed to be installed.

I decided to give installation a shot anyway and see how things would go, knowing I can drop in new floor pans or patch in areas later if it didn't work out. So one of the first steps was positioning the cut templates under the car and tracing out a cut path. They are positioned based on where the weld seam is along the side of the car along with a distance from the subframe connector. In hindsight using the seam as a reference was not the best idea; it's not exactly straight. I'll explain more further down.

I cut the floor using a 4.5" angle grinder and a cutoff wheel.*Peek-a-boo!

I was happy at first to find the connector was fairly tightly fitting on either side, but as a looked around I discovered a few fitment issues which I could have avoided. First in the photo just below you can see there is some gap at the back of the connector. I later trimmed a bit more so it would slide back further and meet the "frame" at the back of the car.

The other major issue was the left-right alignment did not match up with the rear frame. This is probably a direct result of using a generic reference dimension DSE provided from the weld seam to position the cut template. All I had to do to avoid this when I installed the other side was to measure my car myself and position the template left-to-right based on references from my own car rather than the provided dimension. Lesson learned. Ultimately I corrected this by trimming more of the floor away, but that did leave some gaps which were difficult to weld.

The other area of fitment that is imperfect is back where the notch of the subframe connector wraps around the existing floorpan structure to meet the frame. This notch is needed to angle the connector into place, but it leaves 1/4-3/8 gap area. When I called DSE they said they just fill weld this gap, but given how thin the sheet metal is I plan to make a small plate to fill this area before welding. This is one area I have currently left unfinished because to fully weld around the back of the connector I need to remove the leaf spring perch and get some fuel and brake lines out of the way. I will come back to this soon as I have a few other things I need to do under the car around the same time.

Lastly the front of the opening had a very sizeable gap with the top of the subframe connector. Luckily this was very easy to remedy with a hammer. A few strikes and I was able to bring the sheet metal down to the top of the connector before welding.

Once I had the connector fitted, the first thing to weld was the end cap at the front of the subframe connector. I should mention fitment involved trimming the front of the connector back by about 1/2in, which provided more room for installing and room for this end cap so the connector didn't interfere with the subframe. It was a happy moment for me to be welding on the car again, since the last time I did any significant welding was when I narrowed my rearend a few years ago. I'm not sure why I decided to weld in shorts - it was probably pretty hot at the time since this was toward the end of Summer 2020.

With the end cap welded and cleaned up, I fit, clamped, and tack welded the front brackets with the connectors in the car. One thing you may notice in this photo is the shape of the brackets has a little notch at the top where they meet the subframe. On this side I left it as shown, but I realized when installing the other side that it fit better and I could get more weld length if I just cut that little notch off and had a simple diagonal along the entire front.

After those were tacked I took the connectors over to the bench and made some of the most satisfying welds I've personally ever made. For sure the are not perfect, but I am really proud of these.

Once that was done, I went on to more challenging welding in the car. I used a jack to keep the connector flush against the floor crossmembers before tacking everything into place. Then I went to town welding all the thicker materials like the front and rear connections with the frame and where the connectors met the floor crossemember.

All along the most concerning area for me was welding the floor pan sheet metal to the connectors. The sheet was likely around 20awg originally, but many areas were thin due to rust and there were a few gappy areas too. To make matters worse I needed to weld thick to thin and I have very little experience with sheet metal welding. So before I did anything on the car, I cut cards out of the floorpan remnants, cleaned up the edges, and did a bunch of practice welding at the bench. At first I tried a series of small tack welds. This did not work well for me - either the welds came out too cold or if I turned up the heat they just burned right through. You can see just how bad the metal was from the passenger side in these photos

Eventually I settled on a method using stitch welding. As I welded I focused the wire on the thicker material and just periodically dipped the puddle down to the sheet, moving my wire in a "J" shape, to connect it. This worked much better and I was able to weld roughly 1-1.5" lengths without burning through. This required the heat to be just a tad lower than what I normally would use for the thicker material. I had to really concentrate on the edge of the puddle here - as soon as it connected with the sheet I had to redirect the wire toward the thicker material.

Welding on the bench and welding in the car were not exactly the same. On the passenger side (shown below) the metal was terribly thin and would burn through easily. But the main problem was that along the sides of the connector the floor had a rib depression creating a crevice to weld down into. This made it hard to keep the wire stickout length short or aim it at the side of the connector. It felt like I was welding cotton candy and I was honestly struggling all the way around. I had to take it very slow and do a lot of filing, chasing crap thin metal around and refilling as I hit thicker stuff. This section of sheet needs to be cut out and replaced, but I did not want this project to snowball so I did my best to make it work. The finished product leaves a lot to be desired, but I don't think it's of structural concern. I plan to replace the pans when I strip the car for paint (some day)

When I did the driver's side, I made some major improvements by hammering the sheet metal flat so I wasn't welding down into a crevice. Plus the metal was mostly free of rust damage so my job was much easier there.

The last step to getting back on the road was cleaning and laying a coat of self-etching primer to protect the metal.

Then I spray bombed the underside black, except a masked off section at the rear where I still have some finishing work to do.

That brings things up to speed on the subframe connectors. They are not done done, but they are mostly done. At a later date, I will finish weld the rear areas I could not access, and refinish the interior floors + seam seal. All in all I am happy with how they turned out and I definitely like how low profile & integrated they are under the car. DSE makes a good product. Bolt-in connectors would be much easier but I think the integration of these is worth the admittedly high effort.

Ongoing 70 Nova build:
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