Hi,

I've bought some replacement Sills (Rocker panel in the US) for my XJS.

The Sills have arrived but unlike the OEM sills they're not completely smooth around their radius. Rather they are manufactured with lots of little steps which change the angle to create the curve.

I am guessing I am going to need to use body filler over this panel to smooth out this "stepping". Is there a good technique or method for doing this?

I was probably just going to overfill over the panel, and then block it with long block with little or no give in it (such as wood backed block) rocking it up and down over the radius of the panel.

Any advice is great appreciated.

Pictures would help greatly.

The sills are currently off the car.

I hope these photos demonstrate what I mean.

Check to see what the reproduction panels are covered with. Wipe with a rag soaked in lacquer thinner. If it comes off, take it all off, then run over the surface with 80 grit to provide scratch and shoot two - three coats of epoxy primer making sure to give flash time between coats.

This may provide enough build so when cured (24 hours or more) you can block sand it smooth. Filler can also be applied over the epoxy if necessary.

If the coating doesn't come off with lacquer thinner then you have a couple of options:

You will need to scuff the surface with a Scotchbrite pad until dull. I would use a Maroon (some call it Red) pad.

Once scuffed clean it with W&G remover and let flash.

Option 1 (easier)
Shoot 3-4 coats of 2k build primer. Waiting the proper amount of time between coats is critical.
Once cured apply guide coat and block sand to remove guide coat.
You should always block sand in a 45 degree angle but especially over a curved surface. Work it both directions.

Option 2
Shoot with two coats of Polyester Primer (Evercoat G2 Feather Fill is what I use) as it is like a spray on body filler. This stuff chemically hardens so if you haven't used it before please read up on it first and follow instructions.
After and hour or so, guide coat and then block sand to remove guide coat.

Others may have suggestions as well.

Thanks for such an informative reply, that is going to help me a lot .

One quick follow up question, how much of that would you do on or off the car?

I reckon welding and getting it into shape might end up messing any work up that I do off the or ruin the primer's finish.

You will need to install them first. Don't be surprised if you have to cut and modify them slightly while installing. I have found that very few reproduction panels fit perfectly.

Take a good look at how the originals are fitted, front, back, along door, etc. I like to take pictures of everything for references later when installing.