Monday, March 30, 2015

Rear transition pan metal work, part 2 - Passenger Side pan patches, holes, and cracks

1967 Ford Mustang Fastback rear transition pan repair Now, on to the passenger side metal work! On this side we have a gaping hole, a cracked flap, and a bunch of holes to fill. Elapsed time is about 15 hours over four days.

Here's what it looked like when we start. Oily, dirty, and extra holes and screws.

Here's the inside at the same location:

Cleaned up the bottom with Simple Green degreaser, then wire wheels on an angle grinder.  Now you can start to see the extent of the damage. I have no good explanation for that flap of metal in the upper left of the pic. My best guess is stress damage from the air shocks.

Close-up of the flap and a lot of the extra holes that need to be filled.

Cleaned up the inside in the same way. In fact, I sort of got carried away with the angle grinder and just kept going...

After it was all cleaned up, I sat and stared at this mess for a couple hours trying to figure out the best way to attack it. "Paralysis by Analysis", they call that. In the end, I just marked the biggest holes, got out my cutting wheel, and went after the worst part.

Bad metal cut out...

Bend the flap up and away to make cutting easier...

And, zing! New holes in the floor!

Here are the offending pieces cut out of the car. Save these for templates later. Especially in the case of the bottom one. The top piece has two curves to the surface, the bottom one has FOUR. Much hammering on that patch will be needed to shape it correctly.

Clean the exposed area in prep for welding. MUST be clean for MIG welding when using gas. Prep work here is 90% of what makes this work.  Notice the piece of metal I welded to the floor in the right edge of this shot. It's specifically there for the ground cable for the welder. Good, clean ground is part of the prep work.

First patch is in. Went pretty well. It's less stressful when you know no one will ever see it.

Ready for the second patch (see my ground clamp on the right?)

Using the old piece, I mark a bigger-than-needed piece of 18 gauge metal fo the patch.

And, whoop, there it is. What you can't really see well is the multiple curves both horizontal and vertical to get the edges of this piece to line up all the way around the perimeter. I bet I spent 3 hours on this alone. The magnets hold it in place for welding. I use these, but first I'll grind the red paint off the edges so it'll conduct current better for the welder, and be sure to do the tack welds as far away as you can - the magnets will interfere with the arc on the welder. So, tack, relocate magnets, tack again, and repeat as needed. After four or five tacks around the edge, you can toss the magnets.

Patch is in and started to clean up the welds. I guess if I was a better welder, I would have less grinding to do.

Filling the extra holes. The remaining holes are fine, they're for the inner seat belt bracket.

Filling holes and cracks on the backside as well. Didn't need to pull the metal around on this side like the drivers side, so that was nice.

Welds mostly cleaned up and seat belt bracket welded in place (two plug welds from the top side).

There are some subtle dents in the pan for some reason. I hammered some of them out as flat as I could get and will still have to come back and do some final grinding/clean up work. But overall, I'm pretty happy with this area.

Sunday, March 29, 2015

Rear transition pan metal work, part 1 - Drivers Side pan patches, holes, and cracks

1967 Ford Mustang Fastback rear transition pan repair There's lots of work to do in this area, so I'll break it into parts. Overall, from start (here) to finish (primed metal) took two and a half months of working on it every few days for a few hours at a time. I'd be faster if I knew what I was doing.

First, gotta clean up the surfaces and strip them down to bare metal so I can weld on them. Top and bottom surfaces get stripped with a combination of wire wheel and strip-it disc.



I'm going to fill the holes from the old exhaust screws and those weird sheet metal screws and weld the crack shut, but first the gap between the floor pan and transition pan needs to be closed up. For whatever reason (stress), there's some separation between these pieces - maybe 3 mm or so, but in order to weld those holes shut properly they need to be snugged up tight. My Bright Idea is to pull the gap in with some grade 8 nuts and bolts. This works eventually, but 14 gauge metal doesn't want to move easily. Fortunately, I have some freakishly large arms and amazing kung-fu grip, so I got them close.

I had to drill the holes out a little to fit the bolts in and then tightened until I closed the gap (mostly). Then close up the holes by removing one bolt/nut pair at a time and weld that hole shut.  That extra-looking piece at the bottom of the pic above is a spacer - it won't stay.  And for fun and good measure, I added some extra welds at the seam. Not stock, but stronger. Eventually that seam where the panels meet gets covered up in 'seam-sealer', really just a fancy sort of caulking for auto body work.

Here's a close up of the crack in the transition pan - also visible are the holes that were left from the sheet metal screws.

The crack gets welded shut in two steps - first, a hole is drilled at the top of the crack to keep it from spreading (a 'stop-drill') and then welded shut from the top the bottom. It looks rough now, but I'll come back and smooth this out later.

Next up is the giant hold that used to be a seat belt bracket.

The hole is traced and cut out and fitted with a square patch piece of 18 gauge metal.....

...butt-welded in place...

...dressed the welds ....

...and Blam-o, it's patched!  And, yes, a square patch is way easier than that last one I did. Then I screwed up filling in one of the holes under my pretty new patch and had to cut and weld another mini-patch to fill it. So, the penalty for cockiness is more practice.

I also drilled new, correct holes for the replacement seat belt bracket and the dual exhaust hanger bracket.

Except for clean-up grinding, metal work is done on this side; next up is the passenger side, and then upper section that has a long list of little issues to fix.

Monday, March 16, 2015

Rear floor and Transition Pan Assessment

1967 Ford Mustang Fastback rear air shocks damage I really need to do more than one of these a month. But I rationalize my blog-slacking by telling myself that either (a) it's better to spend time in the garage making progress than it is to post about it, or (b) new episodes of Game of Thrones are available on Netflix. I've been doing a little of both. Remember, I'm still catching you up on what's happened so far, and there's more to come.

So, recall when I tore the interior out of the car and the backseat looked like a crime scene?

I need to provide a context image so you can even tell where in the car this is. This is the rear of the car, where the back of the floorpan meets the transition pan that goes into the the trunk. Essentially the backseat area:

 (This lovely inspirational shot is actually this very car from "a few months in the future")

If you look at my floor pan, you'll see an amazing array of surfaces: paint, rust, seam sealer, roofing tar(?), brazing brass, dirt, and some sort of - muck. In addition, please notice that under that horizontal stripe of roofing tar is a series of flat head sheet metal screws (non-stock), and a row of nasty looking weld blobs. The brazing lines show where cracked metal was brazed together, roughly. at the shock absorber access ports. Brazing is closer to soldering than welding, so it's not a great repair technique for structural parts but was common in body work 'back in the day'. After a lot of scraping and scrubbing to get the muck and old seam sealer off the metal, here's what we have:

Looking at the bottom of the floorpan in the same area, there's more damage - several cracks, gaps, and those same holes through the floor where those huge lag screws were holding the dual exhaust hangers in place.

Here's the bottom of the drivers side floorpan (before cleaning). The seatbelt brackets that should be spot welded to the bottom here were in fact just held in with screw tension to the seat belt. Technically speaking, this would be called 'dangerous'. It certainly would not have held anyone in place in any accident. Also please note all those little screws poking through the metal at that horizontal seam (where the floorpan is welded to the transition pan)... that is not factory work.

The passenger side of the floorpan, bottom view (before cleaning). Too many holes, no seat belt bracket, more screws, and in the upper left please note the cracks in the metal of the transition panel.

Cracks, gaps, holes - what can we learn here?  First off, the lag screws that held the exhaust system in place that went through the floor (and the rear seat cushion) tell me that the dual exhaust is likely not stock. Mustangs equipped with dual exhaust from the factory also had a reinforcement plate installed to the floorpan (you can see them in Mr Miller's shot). This car has no such plates. But the plates are available to buy, and they get welded to the floorpan, so I'll just get those and put them in because I want to do a proper dual exhaust system and not have it pull giant holes in the floor. Again.

Secondly, the transition pan is such a horror of holes and cracks that there has to be a reason. The short story is that I think it comes from the air shocks I took off the car when the rear axle came off.

What's the problem with air shocks? Remember, the Mustang is a unibody car - not 'body-on-frame', like Dad's Chevelle (Elvira!) or other muscle cars of the day. In those cars, you can separate the body (where the interior lives and the shape of the car comes from), and the frame (where the engine and suspension mounts are). In a Mustang, the body IS the frame - the structure of the car has been designed to handle the loads and stresses of the engine and the suspension at specific points. (This is why if someone says they did a 'frame-off restoration' on a vintage Mustang, you should be very suspicious.)

For the early Mustangs, the rear suspension consists of a live (solid) rear axle and leaf springs with shock absorbers. The points that take the majority of the stresses are the leaf spring mounts fore and aft. The shock absorbers simply dampen the spring motion and the chassis movement, and help keep the rear axle located in place relative to the road - they are not meant to carry the weight of the rear of the car.  Air shocks are not standard, fixed-height, fixed-rate shocks like the factory installed. Air shocks are just that - inflatable shocks that you could fill with air so you could lift the rear of the car up and change the ride height of car. Remember way back in the day when everyone wanted that cool jacked-up rear end in their muscle cars?

Air shocks are a problem for two reasons here because not only do they change the suspension geometry in the back of the car, but also if they're inflated too much they take the load off where it's supposed to be (the leaf springs) and put it where it's not supposed to be (the shock support/transition pan in the floor). The leaf spring supports are some of the thickest, stiffest metal you'll find on these cars, whereas the shock transition pan is not.

So, in my humble opinion, the air shocks that were on the car when I got it, placed a bunch of stress on the transition pan and likely was the direct or indirect cause of a lot of this mess.

The upper shock mounts have cracks, the upper shock mounting access holes have cracks that have been brazed as a repair, and in general it appears there were some real stresses that caused the spot welds to split and were then 'repaired' with a bunch of self-tapping screws and some globby-looking welds.

It appears that there are at least four separate metal patches that have to be installed, cracks to be filled, holes to weld shut, and panel gaps to close up. All this of course after it's cleaned up and stripped to bare metal. The good news is I don't have to actually replace the whole thing, just patch it up and put metal back in there. Plus, it's a great place to practice welding on the car as this entire area will be pretty much hidden from view once it's done.

The next few posts will detail how all this got done.  Trust me, while I'm no expert, I'm much happier with the finished product. Stay tuned!