Floor and Heelboard

Mini 1275GT Resto-Mod, Dec-2011

Here the floor & heelboard were replaced with new half floor and half heel board sections. This meant that the exhaust tunnel could be retained (which was in good condition) which helped hold the car together and retain some rigidity. This would help ensure that everything lined up on reassembly.

Before cutting out the rotten sections, the car needs to be braced. Here its braced across the door aperture on both sides:

The floor & heelboard work was done with the front subframe and engine left in situ. Ideally, you’d remove these also but I left them in due to space constraints. You just need to make sure the front of the car is supported under the engine so as not to flex the weakened structure.

Once the rear subframe is removed and the car is braced and firmly supported I started to cut out the rotten panels. Firstly I had to remove a section from the lower quarter panel to get at the sill-heelboard-rear subframe mount. Note that the size of the removed section is dependent on the repair panel you intend to use. i.e. If you are going to fit the type of doorstep panel with the integral lower quarter repair then you need to match the cut-out section to this. In this case, a new repair section will be fabricated:

Fitted the new flitch panel temporarily to mark the old flitch for cutting:

Then the flitch, floor and heelboard halves can be cut out. Note that the existing doorstep is left in position and attached to the cross member. This is to provide the alignment guides for the new floor sections. If the doorstep becomes detached from the cross member, then you’d need to add an additional lateral brace from door post to door post as the door post can spring out and you will lose the reference point. It also helps to make lots of measurements before you start cutting (e.g. sill to sill front and back, width of the door aperture top and bottom, etc) as a cross check when fitting new panels.

Then the new floor and heelboard sections were offered up for trial fitment. This took a lot of patience as I needed to firstly trim the new panels slightly over size then repeatedly trim small amounts until a neat fit was achieved for butt welded joints (aimed for about 1mm gap between old and new panels).

A simple jig was fabricated to ensure correct positioning of the heelboard sections. Just used a piece of right-angle steel and tack welded a couple of plates at each end that are bolted to the rear subframe. This gives you a perfect jig for aligning the new heelboard half:

The new floor and heelboard sections ready to fit. The join areas have been cleaned of paint and primed with weld-through primer:

The floor and heelboard are now tacked into position:

Note the spirit level on the crossmember. I levelled the car (measured across the floor, the front panel and rear shock absorber mounts) before starting to cut metal. Then once the old sections were removed and the new panels were fitted I could monitor the level to help ensure the car was kept “square”.

The passenger side is just a repeat of the driver’s:

Passenger side heelboard half in position, supported and braced and located using the jig described earlier:

And the passenger side floor tacked-in and checked for level.

So thats the floor almost done, just needed to seam weld the joints all the way round!

Panels used:

  • Genuine Front to Rear Floor Panel – inc inner sill – RH – 1976-2001 HMP441004
  • Genuine Front to Rear Floor Panel – inc inner sill – LH – 1976-2001 HMP441005
  • Subframe Rear Mounting Repair Panel (Heelboard) – RH: HMP441006
  • Subframe Rear Mounting Repair Panel (Heelboard) – LH: HMP441007