MGB Floor Pans, Parts and Reapir

Those of you who own a fine British Sports Car, whether it’s an MG, Austin Healey, Morris, Triumph, Classic Mini, or any other, you know that rust is a problem.  You owners in the southwest don’t see it except as surface rust, but in the northwest and northeast, we have rust.  Usually we have to attack it where is shows the most, such as on the fenders or rockers.  The one place we really hate to find it, and where it is usually found, is in the floor pans.

Here is a picture of a early ’74 MGB interior.  At first glance it seems to be OK.  What I can’t show you is that if you sat on the seat, drove down the road and hit a bump, the seat would have fallen through to the exhaust pipe.

So what do you do?  Well you need to replace the floor pans, obviously.  I won’t lie to you, it’s a major job.

Our crew requires two full days to do the job.  The hardest part is to remove all of the rusted metal.  Sometimes you can get away with removing only partial areas, but be sure you get all of the rusted material out of the car.

The next step is to clean and rust treat the metal that will stay with the car.

This is the step you should take your time on.  If you do not treat the rusted areas properly, they will come back.  I know that the car will not see the conditions or use that would really cause the rust to reoccur, but if you’re going to work this hard, you need to do it right.

Now that the area is prepped, it’s time to fit the new floor pans.  Here’s where we want to point something out.  If you are replacing the full pan, order the Moss Heritage part.  It costs more, but the fit, and the quality of the part save you untold amounts of time and frustration.  The Moss part has the captive nuts in place for the seats, they fit properly, and they have good welding flanges.  If you are going to do just a partial floor pan repair, it might be best to get the economy part, as you are going to cut it up anyway.

Position the floor pan in place.  Make sure it fits flush to the floor supports, and the flanges meet sound metal on the sides.

Once you have the pans in place, and they fit, you can start welding.  A small 110 wire feed welder will do the trick.  You want to weld the edges in short stitches about an inch long, with about an inch space between.  Don’t try to weld the entire seam all around the floor pan, it’s not necessary and it will cause you other problems.  You have to weld the top flanges and you have to go underneath to weld the pan to the lower frame supports.

After the welding is done, you will need to go along the seems from the bottom with some seam sealer.  Cover the entire seam, even the welds.  This material will be all the water protection you need for the seams.

The next step is to protect the new metal you have installed.  We suggest that you use an undercoat spray to cover both the new and old metal under the car.  This will require cleaning some extra areas, and you will have to get some wiring back out of the way, but it will finish the job nicely.  Once that is done, we suggest that you get some spray bed liner and paint the floor pans on the inside.  This not only helps prevent rust, but also make the job look better.

So now the hard work is over.  Just install some good quality floor insulation, new carpet and put your seats back in, and you are ready to go.