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MG MGA - What to do about my floorboards

I've decided to sort out my ignition/carb problems after I pull the engine and send the car to the body shop, so I spent the day ripping out some really disgusting carpet that hadn't been cleaned in decades. I was literally gagging on the dust...

Anyway, here's the driver's side:

http://img144.imageshack.us/img144/3635/dsc08126zx5.jpg

And here's the passenger side:

http://img214.imageshack.us/img214/5553/dsc08125ys3.jpg

I wanted to remove the floorboards so that rust removal will be easier, but I can't get the screws off. The bolts underneath appear to be welded onto the frame, since they're not going anywhere, and forget about using a screwdriver on those screws as they're pretty rusty.

I could just smash up the boards, but I wanted to use them as a model to make a new set. I suppose I could get a drill and drill the screws out, but that seems pretty drastic. Any ideas?

Thanks,

Darian

PS What do you call that acid that kills rust?
Darian Henderson

Hi Darian Try soaking the bolts with teflon based lubricant, and then use an impact driver to remove the serews. There are inexpensve hammer driven impact drivers that work well. If the impact doesnt loosen them, try heating the bolts with Oxy acetelene, or a zap with an arc welder. Any bolts that refuse to come out after this will likely have to be drilled out The rust killer is muriatic acid. Good luck, Glenn
Glenn

My mother in law's gravey.

Kris Sorensen

Glen, won't an impact driver strip the head of the screw? My problem is that I can't get a good grip on it with a screwdriver.

Thanks for the laugh Kris!

Darian Henderson

If you drill the heads off of the screws. Use a hammer & 2x4 block to lift the floor boards from the underside you might save the old floor boards.
Cliff
Jones

Hi
If you are heating, have fire hose ready. I used holesaw. Locate the centre drill to one side of screw and saw between screw and frame. Lift floor. Brake off the remnants of floor plywood around the screw. Use wisegrip to get the screws out. I broke 1/2 of the nuts welded to frame. It is not that hard to make pattern from cardboard. If the floor is not rotted just clean it paint it and leave it.
Martin
Martin

Darian, you only way to remove the ones that you can't get with the other methods is to drill them out. I think I used an 1/8" drill on most of mine and then rethreaded the holes. It takes a long time and a lot of sharp drill bits. Expect to spend one weekend doing this. Many of us have been there and done that so you're not alone.

Good Luck.

Andy
Andy Preston

Thanks, those are some pretty good ideas. I may try Martin's next weekend, especially since I don't have a welder.

The floorboards are pretty solid, actually, but I want to get to the rust that I'm sure is lurking underneath them. They are a little rotten by the driver's side door, but everywhere else is okay.

Or should I just leave it?
Darian Henderson

Darian,
I went through this last summer. I ended up using a larger drill bit than the screw shaft and just drilled into the head until the head came off - it's kind of like removing a pop rivet. Then I was able to pop the floor boards out. I was left with a stud that I could grab hold of with vise grips. With a combination of heat and several days soaking with PB Blaster (rust desolver) I was able to get out all but two. Some I had to remove from the bottom because they were so rusty. The two that wouldn't come out I had to drill and tap. It's not really a fun job but with patience you can get it done.
We also did this same thing for the screws that hold the clamps for the wiring harness on the frame rails. They weren't ever coming off with a screw driver.
Bob
Bob McFarland

Get some Kroil, and spray them down every day for a couple weeks. Try to get underneath as much as possible, and spray there too. Then get one of these:

http://www.amazon.com/8in-Impact-Driver-Set-Bits/dp/B000BHQ1Y6/ref=pd_bbs_sr_5/002-7304542-2722425?ie=UTF8&s=hi&qid=1177305195&sr=8-5

With the impact driver and penetrating oil, with a little bit of luck you may get all the screws out without resorting to extraordinary measures. When my dad and I removed the floorboards from his 1600 project, there were some that just wouldn't budge no matter what. Instead of drill them, since we were going to replace the floorboards anyway, I took a chisel and removed the wood from around the holdouts, so we could lift out the boards. Then, the head was grabbed with a visegrips, and removed as described above. Some of the captive nuts broke off the frame when we did this. I think there may have been heat involved too, but my memory is fuzzy in that regard.
Del Rawlins

The screws are often quite rusty and resistant to extraction. The resistance welded nuts are (unfortunately) fairly easy to break loose from the frame, and you would like to leave them in place if you can. Drilling and tapping type repair work is very time consuming and frustrating. Penetrating oil is slow and very hard work if you intend to save the weld nuts. But there is an easier way.

Start by cutting up and breaking out the floorboards leaving all of the screws in place, but no wood remaining.

Use an acetylene torch with a small neutral flame. Heat the resistance welded nut from the bottom, just the nut and tip of the screw, not much heat in the frame rail. Stop heating as soon as you can see straw yellow or dull red color in the nut. Do NOT heat to bright red. Do NOT quench. Let it air cool gradually to room temperature.

If these are original screws, and you use a proper #3 Posidrive screw driver with a "T" bar or ratchet handle, or maybe a manual speed wrench (crank handle), you may be able to unscrew them in normal manner after the heating cycle. Otherwise use a ViceGrip, and the screw comes right out leaving the weld nut with a good thread in tact. You probably won't even need penetrating oil. This works with any rusted bolt, even with a broken head, as long as you have enough of the screw protruding to catch a hold with a ViceGrip.

The trick is that the quick heat with the neutral flame litterally vaporizes the rust and dirt on the nut and inside of the mating surfaces of the threads. Once you do a few of these you get the hang of it and understand how much heat (or how little heat) is required. Then you can go all around heating every weld nut in the frame in short order. After cooling remove the screws.

For what it's worth, this is one of the little tricks I learned about 10 days ago at Eclectic Motorworks MGA Sheet Metal Seminar. I had done this before, but I didn't realize how little heat is required if you only heat the nut.
Barney Gaylord

Heat is your friend. I support Barney's idea but add the following:

Instead of the acetelyne torch, a harware store MAPP torch works well. If the head of the screw is broken or the screw is broken at the support bracket, Vise-grips can be used from below and the remaining part of the screw pulled out from below. This is by far the quickest and most sure way to remove the screws. And there will be no repair work to re-install the weldnuts into the floorboard brackets.

Be sure to remove the wiring from the RH underside.

Chuck

Chuck Schaefer

muriatic acid is not correct.your looking for phosphoric acid..cc
c callaway

I did exactly what Martin did with a holesaw and it worked perfectly, preserving the floors for templates. After that, used Barney's heat and visegrips and got everyone out. Bob Prentice
rsa prentice

I used a panel spot welder. I had a heavy duty copper coated carbon center welding rod. Put the ground strap on the frame and applied the spot welder to the heads of every screw. This was in the body of a YA. It also included the boot floor. I was able to unscrew every one without stripping. The current applied to the head loosened every screw.
Sandy Sanders
Sandy Sanders

Lots of good ideas here! I really appreciate it. Hopefully I'll have these off by the end of next weekend...

Thanks,

Darian
Darian Henderson

CSR sells full size patterns for floorboards, complete with hole locations. I have a set, but have not cut floorboards yet, so can't make any statement about accuracy of the patterns. They look pretty good though, and CSR does do quality work.

G Goeppner

You can also get a set of floor boards (undrilled) from several sources, and they are quite economical when you consider the time sourcing good plywood, and the time cutting and adjusting the seven boards.
I drilled off the heads of the screws with a large drill untill the dished washer spun off, and then put a jack under one end of the floor board and jacked it up until it popped off the screws, and then did the same the other end. You have to note the correct sequence of removal as some board edges are over other boards.
Note that the nuts are welded to the floor support rails (you may have missed that point) so do not put a spanner (wrench) on them! You want to preserve as many as you can.
I spent many evenings carefully removing the screws (and there are a lot of them!), but once I had sand blasted the frame I had to replace 90% of the rails with new ones from Clarke Spares (they fit really well), so a waste of time - oh well!
Happy unscrewing.
Peter.
P. Tilbury

So what do you think, should I buy treated boards or not?

Thanks,

Darian
Darian Henderson

I used cheap and common 1/2-inch CDX roof sheathing plywood (putting the exposed knots side on the bottom). I used shopping bag paper and cardboard to make templates directly from the frame. Then I cut the boards to fit, poked a punch through the weld nuts from underneath to spot the centers, and driled the screw holes to match the nut locations. Notice that if any prior repair work was done on your frame the nuts may not be in the same locations as original.

I brushed Penta wood preservative on the boards, multiple coats at 24 hour intervals, being sure to soak the edge grain well. When the wood wouldn't take any more juice, looking a little glossy, I paint it with two brushed on coats of black enamel. I then caulked them in place to seal all edges.

These floorboaards have been in service on my car for 20+ years and 200,000+ miles on all kinds ot roads and in all weather conditions, including lots of rain and some snow and salt. Today they look virtually the same as the day they were installed, and shuold be good for another 20+ years. Nothing special about the plywood, just well soaked with wood preservative before painting.

I wouldn't recommend any special wood unless you intend to shortcut the preservative step, although CC or AC plywood would eliminate exposed knots on the underside.
Barney Gaylord

Hi Darian. I am amazed that Barney's floorboards have lasted so long. My car is exposed to conditions very similar to that of Barney's Regrettably, I have been forced to put 3 sets of floorboards in my car over a 26 year period. The first time, they were just painted, the second time they were saturated with cuprinol wood preservative several times and then painted. I took great pains to make sure the edges were well coated. The wood preservative didnt seem to make much of a difference, since they rotted and de laminated almost as fast as the first set! The last set of floorboards I put in a few years ago were completely encased in fiberglass resin which was applied with a roller. After the resin cured they were painted black. Lets see these suckers rot! lol, Glenn
Glenn

I used 3/8" marine plywood. I painted them with several coats of black paint. As this is not a daily driver, I suspect the floorboards will outlast me. The original ones had been undercoated when new along with the rest of the underside of the car. They were still useable, but I replaced them as I wanted to start out new everywhere I could.
Ed Bell

I got all my screws out the way Barney describes, although I used a plumber's style propane gas blow torch. I then ran a tap through all the threads to clean them up.

Like others, I made my floorboards out of marine ply. Sealed them with preservative and varnished them. Lasted 9 years as a daily driver without any sign of deterioration.

Steve
Steve Gyles

I went with the more expensive marine ply. I did not want to go thru this effort again. I'm getting older and I don't bend as easily as I used to. Bending is not required while the body is off. but if I just had to replace the floorboards, then getting into the footwells would be virtually impossible in 15-20 years. The extra money was worth the insurance.

Chuck
Chuck Schaefer

Well, that gives me an idea. Seems that I'll have plenty to do when my car goes to the body shop in five weeks.

Cutting the boards myself doesn't bother me. I'm a beginner as a mechanic but pretty handy with wood.
Darian Henderson

Can I just say what a pain this is to remove these screws? Definitely the worst part of this rebuild.

But I guess it comes with the territory...
Darian Henderson

Darian

While you are down in the floorboard area, for your own historical purposes, you might want to look to see if the the chassis frame welding number and the car chassis number are still visible.

The welding number is stamped on the cross member just infront of the left seat. It will be between 2 and 6 inches outboard of the tunnelling on the front edge of the crossmember. There will be a letter followed by a number of digits. The letter apparently refers to the team that welded-up the chassis and the number relates to chassis production. If you can read this number, I will give you the email address of the chap who is compiling a database on the subject.

On the right hand chassis crossmember, in a similar position outboard of the tunnelling but to the rear of the crossmember, is stamped your car number that should be the same as that on your plate in the engine compartment.

On many cars, age has taken its toll and these numbers have eroded away.

All part of the hobby.

Steve
Steve Gyles

Hi Steve,

I looked, but I wasn't able to find the numbers you were talking about. If they show up after I clean it a bit, I'll be sure to let you know.

Thanks,

Darian
Darian Henderson

I've never found any of the stamped numbers, though I haven't looked too hard. As soon as I get organized and set up to sand-blast, I've got 7 different cars/frames that I can blast to try and find them.

Derek Nicholson

Darian and Derek

There is a very good article about all the numbers, including exact location and font size, in the MGCC 2005 Year book.

I stripped back the paint on my crossmember and, with the aid of good magnifying glass was able to make out the letters and numbers amidst the general surface corrosion on a 50 year old lump of metal.

I can email you the article if you wish.

Steve
Steve Gyles

I'd like that email.

Thanks,

Darian
Darian Henderson

Darian

I have emailed you the article.

Steve
Steve Gyles

This thread was discussed between 23/04/2007 and 03/05/2007

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