The MGA With An Attitude
Body Sill Replacement - RT-614A
Hole In Top Of Sill
This page is a two-and-a-half-year-later addendum in reference to a single hole in top of the body sill at front of door opening. Someone noticed that I had omitted this hole from the box panel drawing. Indeed I had originally forgotten this detail on the drawing, so now I get to correct the little omission.
This is what it looks like after final assembly, including correct original style weather seal (above left). When I pull up the seal edge it reveals a small hole in top of the rocker panel (above right). This is an intended drain hole. Given this hidden location under the weather seal, the hole is surely intended to drain water that would get behind the weather seal by intrusion at the top where rain water runs between the door top edge and body cowling (or front fender rear edge). Assuming water would run down behind the seal, this hole is located at the appropriate point to drain the water before it runs out from under the seal at the bottom, and to prevent water from being trapped under the seal.
You may notice the hole in the rocker panel is dimpled downward to act as a funnel collecting water from the surrounding area and directing it into the drain hole. A matching (larger) hole in the sill inner box panel should be located directly in line below the hole in the rocker panel. That hole in the box panel was 5/8 inch diameter plain, no dimple or flange. With these holes aligned, water drains through the rocker panel, then through top of the box panel (inside the box sill), then should drain out of the box section at the first (forward) 2-inch slot. There are also small holes in the inner sill flat panel aligned with those slots, so water can drain out of the sill (inboard direction) without being trapped by bottom edge of the outer rocker panel. The whole intent is to allow water to drain away, and for the body sills to be vented for air drying once rain stops and humidity drops.
While in process I did best I could to put the matching (larger) hole in the box panel in the exact original location. I made this hole after forming the box panel, locating the hole as found on the original (rusty) parts. The lower hole is there (both sides) as may be seen in several previous pictures. The lower hole is not visible in the picture above, partly due to parallax.
You would have to look straight down from the top, and I can't get the camera into that position with the car completely assembled. Also these holes are not exactly aligned coaxial. My larger hole in the box panel is about 1/4 inch rearward and outboard from the smaller hole in the rocker panel (same both sides). Looking directly from above, one edge of the larger lower hole is overlapping the smaller hole by slightly more than half the diameter of the smaller hole (see image at right).
The hole location I finally put on the box panel drawing would place the larger hole in the box in line with the smaller hole in my new rocker panel on my car. This may or may not be as original, and it may or may not line up on your rebuild. I would like to think I got the larger hole correct in fabrication, and the smaller hole may be mis-located in the new purchased rocker panel. I may never know which (if either) may be right or wrong, but in the real world of rebuilding body sills it makes no difference either way. There are lots of places where various parts or features can be slightly misaligned, and original factory tolerances were not particularly tight. So it should be no surprise if these holes are not exactly aligned after this rebuild. Given it to do over, I would leave the box panel blank until it was test fit to the car along with the outer rocker panel. Then poke a marker through the small hole to mark the center location on the box panel, followed by making the larger hole in the box at that location (sometime prior to welding the rocker panel in place).
Much ado about very little, just being thorough.