MGB - floor pans (Part 3)

Continuing the effort of replacing the floor pans. In Part 1, I talked through decisions about parts and methods. In Part 2, we removed the old pans. Today, we focus on prepping the new pans and getting them welded in.

Context

paint from below, p-side

Remember that the original pans were spot-welded to the rails. This was done at the factory where very long spot-welder arms are available and things like the doors, dashboard, etc aren't yet installed, so there are fewer obstacles. Even with some crazy-long spot welder extension arms, you will not be able to avoid another solution for some of the mounting locations. Your options: seam weld from below or plug weld from above. At least on the right side, the wires, tubes and cable make a seam-weld from below option very difficult. Most do-at-home folks go the plug-weld route. The folks at British Auto Works in North Plains run seam welds around the outer edge from above, but plug weld the inner frame rails. If you're going to do this, they recommend running beads that are about an inch long and space them every couple of inches to prevent warping. It will hold at least as well, if not better, than plug welding the whole thing.

Fitment

p-side pan prep

The passenger floor fit like it was supposed to fit. It literally dropped right into place. It wouldn't shift too much side to side or front to back, but my hammer/chisel work bent some of the edge along the transmission tunnel, so I had to work the metal back into shape. Once the floor was stable (no wobble or weird clunks from my stepping on it), it was ready to go. The driver (left) side, however, did not fit right. The front right corner on the pan assumed the floor had a squared-off point to it, but my floor had a rounded edge. I had to bend the corner of the pan to test fit and then cut it off with my grinder for welding it in. It would not naturally sit flat either, so I had to be extra careful as I did my first few welds to get the floor to hold flat. You may experience a similar situation, even with the OEM pans. We know the aftermarket ones don't fit without cutting, so be advised.

What's a "Plug Weld"?
A plug weld is performed by drilling a hole through one material, setting that on top of a second piece of material and welding the two pieces together through the hole. In our case, we are making 1/4" holes in the new flooring. The weld is formed by setting the MIG wire into the center of the plug hole, pulling the trigger to start forming a puddle and then extending the puddle into the floor after the puddle has started to grab into the frame rail. Before we can weld, we need to poke holes in the floor, but where? I tried 2 methods. I'll explain them next.

Option 1 - Paint and Measure
Once the frame rails are clean, you just can't help yourself. You just have to drop the new floor on there and admire how nice it looks. It looks so pretty. Looking at the passenger-side pan sitting there, I wanted an easy way to spot the holes. I fiddled with the pan to make sure it was exactly where I wanted it and then set some tool boxes on top so it held still and firm on the rails. Then, I grabbed a can of white spray paint, slid underneath and spray-painted the edges of the frame rails where they met the underside of the new pan. When I lifted the pan off the rails, there were clear white lines showing where the frame rails were. I ran blue tape along those edges and marked drill holes every inch or so with a sharpie. The p-side prep picture on the right shows what the prepared pan looked like.

Option 2 - Use Old Flooring

using old floor, d-side

When I removed the driver (left) side floor pan edges, I didn't crumple them up as I went. Instead, I would separate a section and then cut it free with tin-snips when the trim started getting in the way. Once all of them were free, I arranged them on the ground with the larger sections I had cut out earlier. With the puzzle so completed, I could see where the old spot welds were. So, I arranged the puzzle onto the bottom of the new pan, and shot spray-paint through the taped-on floor-pan edges. When I removed the old edges, I had dots showing me where to drill the plug-weld holes.

Drill Baby Drill
Regardless of which method you choose, drilling the plug holes is a two-step process. First you drill a pilot hole and then you drill out to 1/4". I suppose a step-bit would work so that would be only one drill effort. Similar to cutting out the spot welds, this is time consuming. I understand why British Auto Works (and probably most other shops) reduce costs by seam welding the outer edges. For that reason, I drilled plug welds into the floor to correspond to the inner frame rails, and only a few around the outer edge of the p-side pan. My paint-from-below method worked pretty well, though my alignment slipped a little bit and I had a few holes that didn't align with the rail.

On the driver (left) side, I chose to plug weld the whole thing, so that meant more drilling on that pan. The holes I produced with Option 2 were an exact match. They aligned on the rails perfectly. Unfortunately, the holes that cut all the way through the frame rail were now completely exposed as well. The drilling out of a single pan took me 2-3 hours and overall there really wasn't that much of a difference in time between the two sides, even though there were far fewer holes on the p-side. That doesn't math-out logically, but that's what happened. The all-in time at this point is over 14 hours and no pans are welded in yet.

Plug Welding

If the grinding was the best part of Part 2, then the welding was the best part of Part 3. I borrowed a 110V Lincoln MIG welder from my wife's sister's boyfriend, and bought a small 20# tank of "steel mix" gas for the project (cost me $100 for the tank plus gas-fill on craigslist). I've heard these small tanks have 6-8 hours of gas in them, so that should be enough for multiple pan replacement projects. Once I had the passenger side ready to weld, I hosted my wife's sister and her boyfriend for a welding party. The plan was simple: he shows us how to weld, and I keep a fresh beer in his hand. It worked out well for everyone. While he got the welder set up, he taught us with welding scraps from the old torn-out floor. This gave us opportunity to work on pieces that didn't matter, but were the right thickness and material. We ran the temp / voltage as high as it would go (D) and the feed set pretty fast too (just below 9). Because if the thickness of the rails, the high-voltage setting makes sense. For other work, like repairing the rear bulkhead the previous owner cut a big hole in, I'll need to bring the temp way down. Before we were done for the evening, the passenger pan was in, and 3 of us learned how to MIG weld, including my wife's sister. Very fun.

During the actual weld-in, we had setbacks, of course, like some burn-through of the pan when we novices tried to run a bead, or small fires from grease or paint catching fire from the welding. Not to worry, though, they were small enough to blow out. Still, the decision to weld on the driveway rather than the standard low-ceiling garage turned out to be a good idea. We tested a few of the welds just for curiosity sake by banging on them with a hammer and trying to separate the panel with pressure from below. No dice.

I've gone back and forth about grinding down the plug-weld humps. I know the floor is going to be covered with sound reducer, a carpet pad and then carpeting, so no one would ever really see them. At this point, though, I'm trying to get the car on the road before the weather turns, so maybe I'll grind the humps down under a canopy once the weather changes this fall. Or I may just leave them alone, and focus energy on value-adding efforts, which grinding down weld-humps in an area no one will ever see... frankly isn't.

That's it for today. My final steps are seam-sealing the floor edges, and getting some paint or undercoating on the steel pans. That work may not be interesting enough to warrant a post. After that's done, I am going to focus on getting the fuel system and master cylinders re-installed. Expect posts on those efforts soon. As always, thanks for following along.

MGB - floor pans (Part 2)

Today we continue the saga of replacing the floor pans in the MGB. In Part 1 (See MGB - floor pans Part 1), we identified the issue, and made decisions on parts and a method. Today, we get into removing the old pans.

Get Safe

$15 at Harbor Freight

This could be a euphemism for something else, but in this case, it is exactly what it says: safety first. You are going to be cutting and then welding steel. This throws lots of sparks. Your car runs on gasoline which is designed to explode when a vapor meets a spark. When you put these together, my best advice is to remove the fuel system entirely and then wait a couple of days to let the fumes leave the remaining lines. That's what I did, and I'll post on that later. Consider too, that the cutoff wheel throws dirt and dust everywhere so wear eye protection at least. I use a face shield, long sleeves, and denim pants to protest myself. And yes that gets hot in the summer when you're working in the sun on your driveway.

Clear Your Paths
Under the right (passenger in the US) side floor, there are small pipes and cables that you don't want to set your cutoff wheel into. These pipes and cables are held to the floor underside with nuts and brackets, and further held into place with some rubber bits. Remove the nuts and the brackets and pull the rubber bits out. Toss all of it into a ziplock and mark it as part of the right floor. You'll want them later. Let the cables and pipes hang as far out of the way as possible. Among these is the fuel feed line, the vapor line and the main power supply from the battery. All super important.

blue tape the cut lines

I had the brake and clutch pedals already removed from my efforts on the master cylinders (post on that coming). I chose to remove the accelerator pedal as well to improve my access. Since it is held on with a bolt and the cable is held on with a pin, this removal is very easy. Now that my floor has been removed, I couldn't imagine how much harder this would have been with them still in place. Mental picture: you're lying down on the door frame, hips-to-feet sprawled out through the driver-door, with your arms extended into the foot-well with a grinder spinning a cut-off wheel at 11,000 RPM. Getting the cuts right without accidentally catching the underside of the brake pedal sounds virtually impossible. I highly recommend removing the pedals, if you can.

Mark the Spot
Before you grab your grinder, you need to find the frame sections underneath. On the right (passenger) side, I followed instructions I found online, where I drilled holes at the corners of various support structures. I then connected those dots with blue painters tape and then drew on those lines with a sharpie so I had clear lines to follow. This did work, but for the left (driver in the US) side, I thought I could do it with fewer steps. The first step is the same: with one had under the car and the other resting on the top of the floor, tap with your bottom hand at the corners of the beams. Feel for the tapping with your top hand, and keep circling in on the spot by tapping until you know exactly where the spot is. Mark it with a sharpie. On the right side, I drilled a hole. On the left, I just marked it and moved on. I ultimately found that the drilling was unnecessary. There are 2 main under-floor rails, one runs from the transmission hump to the edge under the front seat mounts. The other runs from that cross rail between the legs to the front. In the US model, imagine a rail running straight at the brake pedal. These rails are about 2 inches wide, but there is only about 1/2" lip that it spot-welded to.

not-so-fun part

Measure Twice, Cut Once
This phrase has been made famous by arm-chair trades-persons dating back to the stone cutters in Egypt. Still, its a good practice. Double check your marked lines to make sure that you didn't draw a line through a section of frame. Also consider if your cut-path will send you through any of the cables or pipes you moved aside earlier. Cutting through a fuel line, even if it's empty, really sucks. Yes, I did and I'll explain how I fixed it later. Along the rear edge, there are two heavier sections in the corners that are not to be cut out. They create structural stability and should only be removed it they are not doing that job. My bar had a pretty rusty floor, but those sections were fine. Make sure your cut lines take these sections into account.

The Fun Part
The floor is cut out in 3 or 4 sections, separated by the frame rails. Cut the rear out first. The rear section comes out as one large, nearly square piece, and the steel cuts pretty quickly once you get started. With the rear cut and pulled out of the way, you can see the cable, etc on the right side. Next, I cut the outer of the two forward sections. Again, this allowed me to avoid the cables, etc on the right (passenger) side. Last, I cut the inner section, and it was all pretty clean except I nicked the fuel line for about an inch, leaving a nice gash in the metal fuel line. At this point, I was glad I'd pulled the fuel tank, and let the system sit for a week or so.

The Bit

spot weld cutter

With the main sections of the floor out of the way, it feels like you're really on your way. That's until you start to understand what comes next. The floor was attached to the rails at the factory with a big spot-welder, placing a weld every inch or so along both rails and around the outer edge. Those spot welds are what is holding that last inch of steel to the car. I have read where some folks (who are far more skilled with a grinder than I) were able to cut these sections off without any other tool. High praise to them. I am no way skilled enough for that, so I went the more labor-intensive route.

Hit Harbor Freight and buy at least 2 spot-weld cutting bits. They are small, fit in your drill, like a regular drill bit, but they are designed to cut spot welds. The shiny, silver point in the center of the bit is set into the center of the weld, and then you run the drill at a slow speed to cut the sheet metal around the weld. This allows the rest of the sheet metal to rise from the rail. Each bit is reverse-able, so as you burn out the teeth, you can pop it into a vice, loosen it with a 1/4" spanner, flip the bit and tighten. One bit lasts twice as long... which still isn't that long if you run your drill too fast.

So, now that you understand the weld-cutter, slap a grinding wheel or wire wheel onto your grinder and grind on the remaining bits of floor so you can find the spot welds. Between rust, paint and black-tar seam-sealer, you may have to grind a bit to find the spot welds. If you can't find them all or you don't want to grind to find them, there is an alternative; you just need to be willing to use a framing hammer and chisel.

The Not-So-Fun Part

cleaned up

With your spot weld cutter in your drill, and a framing hammer / chisel nearby, pick a spot to start. I went with the easiest to get to: the rear section. The spot welds are easier to find back here too. Pick a spot weld, cut it out (slowly on the drill!). If the metal didn't make a "ting" noise while cutting, it may not be completely free. Given time you'll get the hang of it where you're not cutting too deep (through the frame) nor too shallow (and leaving the metal well attached). If the metal didn't separate, get under the metal edge with your chisel and give it a couple of smacks with the hammer. Eventually, the floor and rail will separate. Now do that about 120 times. Per side. I spent about 4 hours per side doing this, so be prepared. Now, I do things slower than lots of people, so maybe you'll be a lot faster.

As you remove flooring, the remnant will start to flop around. On my first (right/passenger) side, I just crumpled the metal out of my way. While this worked, I found that by cutting strips in straight sections (using tin snips) was more effective. And, ff you set them aside with the larger sections of floor you cut out, you can re-create the shape of the floor later.

Clean It Up

temporary protective paint

Once all of the spot-welded in bits of floor have been removed from the rails, you're ready to clean up. First, look at what you've done. There is a pile of twisted sheet metal lying on the ground next to your car. The rails have some holes drilled through (I know mine sure did). The rails have like 100 little circles of flooring still attached, there's some rusty spots, some paint, and probably some seam sealer. All of that needs to be taken down to bare metal for welding. Grab your grinder, put in a good grinding wheel and get after it. To me, this was the most satisfying part of the process to this point: Simply grinding away the ugly and leaving a nice clean shiny rail. Once the weld points are nice and clean, I switched over to a wire wheel and removed all of the surface rust I could find in the foot well, along the transmission tunnel and the rear, effectively grinding away all of the rust in the seating tub.

Since I was not going to be working on the project for a while, I shot the cleaned up space (including the rails) with primer and some orange Rustoleum so I wouldn't have new rust appear while I was away. This meant I got to grind that paint off later, but if you're not going to jump right into welding, I'd encourage you to consider the same.

That's it for today. More next time. Thanks, as always, for following along-

MGB - floor pans (Part 1)

Today's post is the first of a series dedicated to the removal and replacement of the floor pans in my MGB. This process would be the same for any car whose floors are not a critical part of the structure. I believe most cars fit that description, but I'm sure there are some unibody cars out there which have particular demands on the floors requiring a little more expertise. On that note, let's be very clear: I have zero prior welding experience. Nada. Zip. I've tried to play with a stick welder and was unable to strike a spark without getting the stick stuck to the target material. After a few hours of that frustration, I gave up, put the welder under my workbench and moved on. Until now.

The Patient

right side floor - before

I have posted quite a bit about the journey with this little British car since I acquired it late last Summer. After a spirited drive home with no seatbelts, no brake lights and little understanding of how it operated, I've made many improvements:

• brakes (link)
• fuse box (link)
• master cylinder / pedal box removal (link)
• engine mounts (link)
• rebuilt the front suspension (link 1, 2, 3, 4) including front wheel bearings, etc
• new seat belts, rear suspension rebound straps, fixed the brake lights (no links)

While working on the front suspension, I had a volunteer in K2 ask if he could help out. I wasn't in a spot where unskilled hands were really a help, so I asked him to start removing the interior. The carpets smelled bad and were pretty worn, so I'd intended on at least getting the smelly stuff out and putting in a temporary solution until I had the cash to do the interior well. That is where this story begins.

Discoveries

left side floor - before

With a 1/2" spanner and a small ratchet, K2 was able to remove the 4 bolts which hold in the passenger seat and pop them into a ziplock baggie. We pulled the seat, and set it on the floor. I left K2 to the carpet and I returned to the suspension. K2 did a great job pulling the carpet free from the floor, and the transmission tunnel. The floor looked fair, with surface rust, but half of it was covered by the original sound deadener. We split the task of hammering that out with a chisel so we could evaluate what lay beneath. There were some rusty spots as you can see in the upper picture, but only pin-holes through.
Prognosis: fair, but will require some work to have them sealed up. Replacement suggested.

With the limited space in the garage, K2 had to perform some gymnastics to get after the bolts holding the driver seat in, but once removed, he made quick work of the carpet and we cleared the sound deadener much faster as well. Unfortunately, as "okay-ish" as the passenger floor was, the driver floor was pretty bad. There were multiple small holes and the sound deadener came out so easily because of the heavy rust underneath it. Upon further examination, the floor around one of the nuts for the seat had cracks in it.
Prognosis: This floor was toast. Replacement required.

Decision made: we'll replace both pans, one at a time, and hopefully have the MG road-able before the next rainy season starts.

Pans

aftermarket pan

When it comes to the floor, there are OEM and aftermarket floor pans. The OEM cost about twice as much, but they have all of the little things that make them easier to work with. They have the nuts for the seat-bolts already installed, and the reinforcements to the floor around them. There are various little threaded studs on the underside that are on the OEM pans. Last, of course, they are heavy British steel. The aftermarket pans do not have most of the fasteners attached, are made with thinner (not British) steel and they reportedly have an extra lip around the edge that needs to be cut off. Based on the pictures, it looks like the aftermarket pans also lack the drains. neat. I chose the OEM pans, and ordered a set through my local MG specialty shop: British Auto Works in North Plains.

Weld or Glue

OEM pan

There is a whole religious war about using a structural glue to attach floors, or other "non-structural" panels. The glue argument goes "modern cars are glued together, and the new glues are far better than anything they had back then so the manufacturers would have used them if they'd had them". Sounds reasonable. The weld counter-argument goes "modern cars are CAD designed with things like cost of materials and time/effort factored into the engineering so the glue is part of the engineering work, the crash testing, etc so gluing anything that isn't purely cosmetic on a non-glue car is a bad idea". This also sounds reasonable. I decided that I'd err on the side of caution and learn how to MIG weld on these floors. I have always wanted to learn how and while floors may not be structural, my seat is bolted to it, so it feels a little more important than, say, a rear spoiler. With this in mind, I reached out to my wife's sister's boyfriend to borrow a welder, and some welding instruction. But, before we get too far down that path, we need to remove the old. We'll get to that next time.

That's it for today's appetizer of a post. More to come on this topic for sure. Thanks for following along.

Happy V-day to me

First, an update on the RIBE:
The RIBE bit arrived yesterday, and it was NOT the right bit. Now, I'm looking at a 6M triple-square (aka XZN) from Sears.com for $8 plus shipping. Unfortunately, they don't stock them in stores. Too bad, as I was in there last night buying a welder. As the guys behind the tools counter said "your wife must really love you" to spend Valentine's Day buying a welder at Sears. Yeah, they nailed that. Its really an early birthday present, and with 2 young kids, opportunities to shop for anything as a couple is near impossible. She wasn't too hip on buying something like that without me there, so it worked out.

Anyway, I have the welder (the Clark 120V Arc-welder) that I've pined for since November, so the engine mounts, radiator mounts & cowling, even the exhaust can and probably will be built by me. This will slow the process down, but so it goes.