I’m currently fitting the bonnet of my S3 2+2 to prepare for painting. I understand as to how move the bonnet front/aft and up/down using the shims at the hinges. In fact, I have already achieved a nice 1/8 inch horizontal gap at the bulkhead. What I don’t like is that it took a large stack of shims to move the bonnet forward enough, but it works.
What doesn’t fit yet is the horizontal gap at the sills on both sides. It is 2 mm wider at the bulkhead compared to the wheel opening. This means I have to add vertical shims at the hinges to raise the front of the bonnet. However, my fear is that I run out of available space/shims before I can raise the front of the bonnet enough.
Would placing a shim between the lower mount of the bonnet support frame and picture frame be a viable option? Or do I have to invest in a new bonnet support frame. The car had been hit in the front when I bought it, so the support frame is probably bent.
Firstly, a 1/8” gap is a little too narrow, by about 1/16” or slightly more. The hinge panel of the bonnet underpan is a fairly stiff 18 ga steel construction but it isn’t absolutely rigid, nor are the bonnet stops capable of rendering the bonnet absolutely immovable. Even when everything is to spec and the bonnet is locked down it can and will flex and move slightly while driving over bumps in the road and with a too narrow gap you risk chipping paint.
You don’t mention your vertical gap between the rear of the wings and the A-posts, which should be even and the same as the horizontal gap. Something is amiss if the gap at the rear of the bonnet is even across the bulkhead and down the A-posts but uneven along the sills. Not shims, or the bonnet subframe. This indicates that either the bonnet or the sills aren’t square, likely the former. Both should be perfect right angles. Easy enough to verify with a framing square. Not necessarily abnormal, and correctable by careful cutting and rewelding of the lower rolled edge of the rear wing quarter panel.
In my case, with the top of the bonnet perfectly level with the top of the bulkhead, the gap between the sills and lower edge of the wings was even but a mere 1/16” wide. This was due to the slightly sharper profile of the replacement MR outer sills. It required some surgery to correct.
You don’t say how much you had to shim the bonnet hinges to achieve the fit you have but if it’s really excessive (say, more than a half inch or so) and the car has been involved in a front-ender it is likely you have damage to the bonnet subframe and possibly to the hinge panel in the underpan. The problem with shimming the lower flanges of the bonnet subframe is the upper flanges will no longer be even with the picture frame and would require a tapered shim to achieve a solid fitment.
Nick, it looks like when you cut the fender you cut off the rolled edge, trimmed the fender then welded the rolled edge back on. In other words you made the cut very close to the rolled edge. Is that right? I assume cutting that close to the roll helps reduce distortion. On the other hand its really hard to planish the weld if its so close to the edge… Just wondering about technique here
I am about ready to do this job myself, my fender is about 1/4" too tall and fouls the sill…
Yes, John. I had to reduce the width of the quarter panel a little more than 1/8", so the cut was precise and close to the rolled edge. The off cut is tacked in place (first pic) then inch long stitch welds spread across the bottom with plenty of cool down time in between to prevent distortion. This is followed by careful grinding of the weld, no planishing and no filler needed. The cutoff piece wrapped around the 1/8" wire is quite stiff and keeps things straight.
thank you for your reply. For now, I come to the conclusion that it’s better to investigate the root cause (frame bent or bonnet underpan bent) than to fight the symptoms with shimming. Even if I find a way to add more shims, it will be a “dirty” solution. I will get back once I have an update.
Hi Manfred, Haveing done a complete resto on my 1979 SII, I would tend to share that as a goal. However, I am not sure how you might best achieve the goal! Mine was not warped so it was not an issue, so I would guess you need a “correct” version in order to make careful comparisons on the whole slew of the bonnet support pieces.Not an easy job to do. Please keep us advised how you manage this ! I know someone who has a similar problem!!
