Monday, September 13, 2010

Combined floorpan halves/heater channel replacement

The complete floorpan pressing is by far the better option, though fitting it is really too advanced a task for all but the most experienced DIY restorers. If the floorpan has rotted then it follows that the heater channels will also have rotted and need to be replaced, and it is essential that the work is carried out in the correct sequence. This is as follows.
1. Internally brace the bodyshell.
2. Lift the shell off the chassis assembly, then clean off all traces of old belly pan gasket.
3. Cut out and replace the floorpans.
4. Bolt the new heater channels onto the floorpans.
5. Cutaway old heater channels from shell.
6. Lift shell back onto chassis. 6. Weld shell to heater channels.
7. Remove shell, fit gasket, re-fit shell.
To begin with, strip the interior of the car. Weld braces across the door apertures and between the two A posts so that the shell will keep its shape after the old heater channels have been cut out. Lift off the shell and clean all traces of the old belly pan gasket from the chassis assembly.
To cut out the floorpans, an air hacksaw is ideal, but an air chisel could also be used if you can stand the noise! Take care not to cut into or distort the flange between the spine chassis top and base sections. At the rear of the floorpans, take care not to damage nor distort the bracket from the damper mounting.
Then, using firstly a % in. followed (if necessary) by a % in. bit, drill out the spot welds which fasten the old floorpan edges to the spine flange. These occur approximately every 3/4 in. on original floorpans. Expect to have to grind out weld at the corners. Clean the flanges.
Prepare the new floorpan by cleaning all edges which are to he welded, then spray a coat or two of weldable zinc-based paint on the internal faces of the joint. Offer the floorpans up, and bolt them only at the rear damper mounting extension bracket, and offer up the heater channels then bolt these into position. The two large bolts which pass through the heater channel into the front of the chassis are then fitted to bring both the floorpans and heater channels into the correct position.
Expect both the floorpans and heater channels to be less than perfect; some tailoring of the floorpan edges might prove necessary, although the most common problem is poor alignment of the bolt holes. On the heater channels fitted to RVJ 403H, the closing (bottom) plate holes did not align with the internal captive nuts, and the metal surrounding three of the holes partially obscured the nuts!
Your typical DIY spot welder will probably not have enough grunt to weld through the two thick spine flanges plus the floorpan edges, so don't go investing large sums of money on very long arms until you have tested the welder on similar thicknesses of steel! The alternative is to continuously MiG weld the joints — not so pretty as spot welds, but no one will ever see the joints anyway! Clean all paint from the parts of the heater channels which are to be welded, and apply weldable zinc paint before welding.
Now cut the old heater channels out from the bodyshell; this is made far easier if the shell is rolled onto its side, with plenty of padding to prevent damage. Check firstly that your internal bracing is still firmly welded so that the shell cannot distort. Cut carefully along the flitch base, around the A and B post base flanges, and below the rear quarter panel. Some 'persuasion' with a lump hammer may be needed to get the heater channels free!
Lift the bodyshell onto the chassis (which now has the new heater channels bolted in place) and carefully manoeuvre it so that the two rear body mounts align with their holes on the damper brackets and the shell sits correctly. Fit the rear body mounting bolts, check again that everything is in line and fit the doors temporarily so that you can see whether the door gaps are right (you may have to remove the cross brace at this point), then gas or preferably MiG weld the shell to the heater channels.
When all welding is completed, lift the shell from the chassis and then fit the belly pan gasket. Some people glue this in place using impact adhesive, but manoeuvring the shell when re-fitting it can rip the gasket out of position unless it is securely held by the recommended fixing method of pop rivets. (See 'Re-fit Bodyshell to Chassis' later in this chapter for more details.)
Re-fit the shell. The accelerator pedal base has to be welded to the floorpan: it is best to leave this until the engine, clutch/brake pedal assembly and accelerator cable have been attached. This will allow you to check that you have full accelerator lever response to the pedal. travel—if you weld the pedal too far away from the
lever, then you could end up with only a fraction of the available throttle lever movement!

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