by Ken McLean

Tech Info Home


Firstly, rust spreads; when replacing the outer sill panels, you will most likely have to repair some rust in other areas such as the bottom of the "A" pillars, the inner sill panels and the front and rear floor pans. Some of this rust will not be entirely obvious until the old sill panel has been removed, so be prepared to be creative with some spare sheet metal because rust replacement sections are not available for all these extra parts.
  1. Preparation.

    Jack the car up and support the body on stands under the crossmembers at the front and rear and under the subframe at the front. Make sure that the car is level and the stands are firmly in place.

    Important! To reduce the chance of distortion - only do one side at a time.

    Remove the front and rear road wheels and the front mudguard. Clean off caked in mud around the bottom of the "A" pillar&endash; This may show the first signs of other "hidden" rust. Remove the front and rear doors.

    Remove the door rubbers. Note that if you intend reusing the rubbers, it may be wise to cut them with a very sharp blade and rejoin them later, rather than try to remove them in one piece. Remove the scuff plates and the front and rear floor mats as well as any other combustible hessian underlay or carpet. Remove the front and rear seats.

    Remove the bolt holding the outer subframe leg to the body. This may require a heavy metal drift and a club hammer, as rust forms around the shaft, making it difficult to force through the hole in the sill panel.

    Carefully investigate the inner sill panel where the front subframe is attached. If there is no rust, or it is only minor, then it can probably be repaired once the outer sill panel has been removed. Major rust behind the subframe leg will necessitate the removal of the entire subframe to repair it properly. This article will not discuss the work needed to remove the subframe.

  2. Removing the old sill panel.

    In some respects this is the most difficult and time consuming aspect of the job, as the objective here is to remove what is unwanted without damaging that which must be kept. I have found the best method is to oxy cut away the outer sill panel to within 15 mm of the spot-welds right the way round the panel. This will enable you to either grind or drill each spot weld and by flexing the strip of remaining outer sill panel, it should break free from the inner sill panel perhaps with a little help from a couple of taps with a sharp chisel. This will allow the inner sill panel to remain intact without having to drill holes right through it, which would then have to be filled later. Be careful removing the old sill panel from the bottom of the pillars. The bottom of the "B" pillar needs special attention, as the original sill panel extends up into the pillar by about 20 mm and is difficult to remove. Carefully drill through the spot welds in the base of the "B" pillar and slowly work on the remaining plug of outer sill panel until it breaks free of all spot welds. Be careful of the door alignment strip down the pillar, it covers a spot weld, and care must be taken not to damage it. On occasions, I have deemed it necessary to cut the bottom 50 mm from the door alignment strip and remove it entirely. The "A" and "C" pillars are fairly clear with regard to what has to be removed, but usually there is more hidden rust in these areas, and care needs to be taken not to damage metal which must be kept. I find that the easiest way to remove the sill panel from the dog leg, is to cut the dog leg with a hacksaw just above the spot welds, because this area has been lead filled from the factory.

    An important decision needs to be made regarding the join between the outer sill panel and the front and rear floor pans. The outer sill is much thicker material than the floor pan and as such, it is very difficult to remove the sill panel from the floor pan without damaging it quite severely. If the floor pans are to be replaced, then the join along the sill panel can be ignored and the floor pan sliced through with a chisel just behind the outer sill panel (see sketch of sill cross section). If the floor pans are to be saved, then a lot of patience will be required here, or some extensive repairs will be needed later when welding in the new outer sill panel. Note: If the floor pans are to be replaced do not remove them from the car until after the new sills have been welded in as this will weaken the body structure and distortion may result.

  3. Repair of rust.

    The base of the "A" pillar has an extensive inner area, which is usually always rusted. You will need to manufacture pieces here to repair the structure and maintain the manufacture's integral body strength. Don't forget to redrill the hole for the subframe bolt if this piece of metal is being replaced. The inner sill area can also be repaired at this time; once again using manufactured pieces. Usually the "B" pillar will not need any work, but the "C" pillar may require a patch panel in the inner sill. Don't worry about the small panel between the inner and outer sill panels until later. Paint the whole inner sill area with a rust preventative treatment.

  4. Trial fit the new panel.

    Trial fit the panel. If you have a NOS sill panel, this will be an advantage, but since they are fairly rare, a reproduced part will fit fairly well, but will probably need to be modified around the bottom of the "A" pillar by a little cutting and reshaping to line up the bolt hole. Once you are happy that the panel fits well and is held in snugly with "G" clamps or welders vice grips, place a few tack welds around the panel so that the doors can be refitted and the gaps checked. Take particular care to not only adjust the distance between the sill and the door vertically, but horizontally as well. It may be necessary to break some spot welds and reshape mating parts to achieve the desired fit. Remove the doors once again.

  5. Welding it in.

    A mig welder is best but an oxy welder will work OK as the complex shapes resist the desire for distortion caused by heat generated during welding. As for all welding jobs, don't attack one area solidly, work around the sill evenly to avoid heat build up and to ensure that the panel stays where you have tack welded. It is not necessary to fully weld the structure, 50 mm welds followed by 25 mm gaps will suffice along the straight edges, but fully weld the bottoms of the pillars. If the floor pans are to be replaced, no welding is required along this join. If you are using the original floor pans, some repair work, and possibly a few patch panels will be needed to bridge the gap between the old floor and the new panel.

  6. The fiddly bits.

    Carefully weld the sill to the "A" pillar taking care to beat the sill into the groove where the door seal fits and the area around the subframe bolt hole. Temporarily reinstall the front mudguard to check its fit around the sill panel. This area should be completely welded in order to keep water out. The "B" pillar will need tapping down into place to fit, and small patch panels may be required to neaten the job. These patch panels should be below the scuff plates when they are refitted. The door alignment strip will need to be tapped into alignment and rewelded at the bottom, or completely refitted as discussed above. The "C" pillar is straight forward, but careful work is needed to line up the dog leg before welding it into place. Now is the time to manufacture the small panel between the inner and outer sill panels at the rear. Ensure that this area is well fitted and caulked, as water from the wheels will splash up here and enter the sill, starting the whole rust process again.

  7. Finishing off

    Reinstall the subframe bolt (note that reproduction bolts are available) and tighten the nut. Paint the area of the outer sill and the base of the "A" pillar underneath the front mudguard with a bituminous paint or equivalent.

    Reinstall the mudguard and bolt into place.

    Install new door rubbers, or if using the originals, rejoin them as discussed above. Reinstall the doors, floor mats, scuff plates and seats.

    Reinstall the road wheels and remove the stands.

This has ben the first in new series of articles covering technical info that is not found in the Workshop Manual. Many thanks to Ken McLean for taking the time to document a procedure he has obviously done more than once!

Important Note: This document is intended as a guide for those persons interested in repairing or modifying their vehicle. The FE-FC Holden Car Clubs of Australia take no responsibility and accept no liability for the information contained herein. You must ensure that all work carried out and/or modifications made to your vehicle are legal in your state, and we recommend you contact an engineer or your local Traffic Authority for further information.

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