1967 Pontiac Lemans budget build - episode three - trunk panel install (part two of two)

Episode one, introduction.

Episode two, trunk panel install part one.

Episode three, trunk panel install part two.

Episode four, door rust repair.

Episode five, tail light panel and rear crossmember.

Episode six, passenger quarter panel.

Episode seven, driver's quarter panel.

Episode eight, floor pan and rockers, part one.

Episode nine, floor pan and rockers, part two.

Episode ten, frame repair and prep, body drop.

Episode eleven, radiator core support and miscellaneous rust repair.

Episode twelve, trunk repair and more miscellaneous rust repair.

Episode thirteen, fender and inner fender repair.

Episode fourteen, panel prep and block and prime.

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For this third episode we're entering part two of the 1967 Lemans trunk panel replacement. What have I learned so far? Well, one thing is something I already knew from previous projects: Cheaper isn't necessarily cheaper. As I noted in the episode two, the trunk pan kit has been a real hassle to install. The stampings are not accurate and the fit is questionable. However, if I had went ahead and spent the money for the one piece pan I would be out $500 but I would have been done weeks ago. 

Assuming of course that the one piece pans are better engineered.

Also as chronicled in episode two, I started by repairing the driver's wheelhouse. In retrospect, I probably should have started with the driver's side trunk panel and built the wheelhouse to conform to the trunk panel. The trunk panel would likely have required less modification. It still is a poor stamping, but building the wheelhouse to the panel would have likely saved me work.

I will embrace this strategy for the passenger side panel.

Here's the finished driver's side, spot welded in:

What changes did it take to get here? Well, I modified the shape of the panel lip around the wheelhouse in order to get a closer fit. I took about an inch off the width (you can see the seam on the left side paralleling the quarter panel). I lengthened the little upslope area behind the wheelhouse so that the flange would drop down to contact the trunk side drop. And I modified and installed the body mount brace. Here's a pic of it attached:

The black at the top is POR-15. I also POR-15'd the interior of the brace and the bottom of the pan that gets covered by the brace. The welding surfaces of both pieces were coated with weld through primer.

You can see in the first photo that the gas tank mounting brace is installed. Before I installed it I painted it with POR-15 and sprayed some weld-through primer on the welding surfaces:

Something to figure out: Since the gas tank braces sit on top of and are spot welded to the rear structure, it means the factory would have installed the braces first. The problem is, because the front of the brace connects only to the trunk panel, this would leave the front of the brace to dangle until the trunk panel was installed and attached to the brace. 

Or maybe they installed the trunk panel before they installed the back structure. Then the back structure would have the braces attached to them already.

Hmm. How would the factory have done this? 

For me, however, I needed to make sure the braces were in the correct position on the trunk pan, plus be able to weld the rear of the brace on top of the structural panel. I decided to install the brace to the left panel, not to the car. I don't know if this was the right strategy, but fitting it before the other panels were installed allowed me access the rear of the brace to weld it. Once the brace is welded the center piece of the trunk panel covers this area. 

The key to placement of the brace is to make sure it is centered where the gas tank strap connects in the T-slot on the back structural panel. The gas tank strap T-slots are 20" apart center-to-center. The center is right where the rise is stamped for the gas tank neck to pass through underneath. To establish center for the front part of the trunk, I measured between the wheelhouses and put a piece of tape there.

Having the gas tank available really helps. There are recesses in the top of the tank where the bottom of the braces fit, also spaced 20" apart center-to-center. That means the brace runs parallel with the centerline of the car, 10" from the center line to the center of the brace. 

The disadvantage of installing these braces like I did is that there is a tendency for the brace to rotate on its axis. Also, as mentioned the brace gets welded to the rear structure, so it has a spot weld flange across its back end. Again because of bad stamping, this area needed to be modified. *Sigh.* And the curvature of the brace did not match the contour of the panel. *Sigh* again.

Now it's time to move over to the passenger side. The first thing to tackle was some rust in the upper area of the existing trunk panel. But the damage wasn't nearly as bad as the driver's side. Since this area will be harder to reach after the panel is installed, it's best to make the fix beforehand:

You can also see that the frame mount hole on this side is rusted to a larger diameter. It will need the same repair as the driver's side. 

Then I test fitted the frame mount brace:

This is before I put POR-15 and weld through primer on it. 

The outside end of the brace didn't have a correct curve where it mates to the wheelhouse, so it needed some hammer and dolly work but no welding. Also, I didn't need to move the frame mount location. Unlike the driver's side everything fit much better. 

For the passenger side spot weld flange I decided to retain the flange of the old trunk panel, because it was in good shape: 

The rust you see along the lower lip of the trunk side drop is actually the bottom lip of the quarter panel, not the side drop itself. Also, when I cut the rust out of the wheelhouse it released the side drop panel to spring out. So I looped some bailing wire (top left of the pic above) to hold it in the right location.

I laid the new passenger side panel down, overlapping the existing panel remnant, and clamped it with some C clamps and vice grips. I got under the car and drew a line along the overlap, removed the panel, and cut it outside the line, leaving a little extra. I then reinstalled it, making sure it was in the correct alignment, and took a cutting disk along the intersection of the two panels. This is a technique youtuber Fitzee calls cut and butt. 

The idea is to overlay the panel and cut through both at the same time. Fitzee does this by putting temporary spot welds the new panel about every 8 or so inches, then cutting both panels only to the next spotweld. The two panels can be pressed into alignment and butt welded. Then the next 8 inch section can be cut and butt welded.

This has two effects: First, cutting both panels at the same time means that any variation in the cut will transfer to both panels, making a perfect joint; and two, the thickness of the cutting disk makes a gap that is weldable (if you do it right):

Here it is spot welded:

I finished up the welds in between each spot weld, moving around to not concentrate heat. I was actually kinda proud of how this fit. It needed no tweaking or adjustment at all. Every part of it lines up. Even a blind squirrel gets a nut sometimes. 

Now on to the center panel. This panel was one of the few things that didn't require a bunch of modification. It's exactly the right width as is, but at the rear there is an offset flange which I almost completely removed. The reason is, I decided to position the three panels underneath the existing rear part of the trunk panel (see above pic, lower right spotwelds). However, there is another structural panel in this rear area. This is the structure which contains the t-slots for the gas tank straps, the spot weld points of the gas tank braces, and also the cage nuts for the rear body mounts. It turns out it is shaped in such a way as to interfere with slipping the trunk panel flange underneath it. 

I don't know if this was how the replacement panels were designed to be fitted, but since there were no instructions I just made the choice and cut off most of the trunk panel flange and fitted it under the existing panel. 

Here's the test fit of the gas tank, to ensure the braces line up with it:

So I painted on some POR 15 in the key places, sprayed some weld through primer, and welded it in:

A light coat of primer and some seam seal:

I used the seam sealer to fill any possible holes in my welding job (I found it's nearly impossible to completely weld in a seam with no holes) and then sanded it off. The seam sealer will stay in the nooks and crannies, which will ensure that moisture doesn't get in. 

I put a couple of thin coats of body filler on the joints so as to make the panel appear to be one piece. Since the filler will absorb moisture and eventually bubble, the waterproof seam sealer should prevent that from happening. I then covered the filler with glazing putty:

Glazing putty fills in the little flaws and scratches, it doesn't require mixing in a hardener, plus it's really easy to sand. The trunk is now ready for whatever finish I decide to put on it.

The underside is at this point partially coated with POR 15, and I'll finish painting the rest of it once I'm done welding the trunk area:

This completes the chronicling of the trunk pan. I moved over to the passenger wheelhouse to finish that, plus I tied up a few odds and ends in the trunk. Final analysis: Despite being a very difficult and time consuming job, The trunk came out flat, level, structurally sound, and looking good. But it required so much tweaking, modification, and just making it up as I went, that I would never recommend a hobbyist do this. 

One should always carefully consider the scope of jobs like these, which even means not purchasing the car to begin with. Knowing that these repairs are difficult might mean that taking a pass on a rusty old hulk is the best decision. 

The next installments will be door repairs and after that the tail light panel install.