Ken:
The floor boards must be welded into place. You can do all the
nasty work yourself, making the job for the welder easy.
****** Don't make stupid mistakes with flammable substances ******
enough said.
First off, the damaged sections of floor have to be removed. You do
not have to remove the entire floor, just the areas that are rusted. The
floor is spot welded to the frame rails. The easiest way to remove it is to
cut out the area along the frame rail, then remove the spot welded bit
seperately. A hammer and chisel can be used to remove the floor metal,
leaving the spot welds behind. This way you are not drilling through the
frame rails to remove the spot welds. A spot weld saw also works well but
is $$$. This work can be done with a sawzall, hammer and chisel. The frame
rails must then be ground smooth. Watch for sparks!!!!! A hand grinder
sends white hot streams of metal a long way. Each spark is capable of
igniting whatever is in it's path. Grinding sparks will also melt many
materials including glass. That's why I now have an interesting rear window
in my works hardtop.
There are two brands of floorpan. The British Heritage one has the
seat nuts and wiring harness studs welded on, but has only a vestigial lip
on the edges. The regular aftermarket floor does not have any welded
fasteners, but does have a large lip designed to work on cars that have
significant damage to the vertical sections of outer rail and tunnel.
Either one can be cut down to spot repair damaged areas. I only
suggest completely replacing the floor if there is major rot. A couple of
holes on an otherwise solid floor should be spot repaired.
Once the floor pan is trial fitted, get out the handy drill and
start drilling holes that match up with the frame rails and sides. About
every 2-3 inches works, YMMV. The holes should be about the same size as
the original spot welds. To hold everything in place I would suggest using
sheet metal screws every foot or so. When you are done you will have the
floors screwed in place over nice shiny frame rails with lots of holes
duplicating where the spot welds would have been.
So far there has been no work that requires anything beyond hand
tools. And you have done all the hard work.
Roll the car down to a shop that can do MIG welding. Instruct the
welder to plug weld all the little holes you have drilled. Point out where
the lines and wiring are and express your concern that these do not need to
be welded upon. MIG welding is precise enough that it can be done without
removing fuel systems with the right precautions.
That's pretty much it. If you have any concerns about fire, by all
means remove the fuel tank and fuel lines. It is not essential, if you obey
basic industrial safety procedures. If you have any questions about safety,
take the car to a profesional shop and let them handle it.
Hope this helps, and doesn't freak too many people out.
Kelvin.
-----Original Message-----
From: Ken Waringa [mailto:kwaringa@dynsys.com]
Sent: Tuesday, March 14, 2000 12:18 PM
To: MG
Subject: Floor replacements
I have a question about floor panel replacements. I have a 79 MGB that has
pretty bad floor panels. The DPO couldn't get the seat bolts our so he just
pried them out, tearing holes in the floor panels. Do new floor panels need
to be welded in or is riveting them ok? I believe these panels are
structural and need welded, but I'm not sure. If they only need riveted, I
can so that. If they need welded, I'll have to take them someplace. If
welding is required, what preparation should I do first? Remove gas and
brake lines? Anything else? I've done a lot of things to the LBCs, but
never floor pans.
TIA,
Ken Waringa
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