Plates/Gussets/Braces/Seam Welding Mods
After bringing my Porsche 911 chassis back from dead, I feel that I’m at liberty to modify it a bit while I’m in there. Porsche did the same thing on their race cars back in the day. Mods such as coil over tower gussets, torsion tube braces, strut bars, stitch / seam welding, light weight materials, roll cages are all weapons of choice by the factory to take a touring car and make it more track worthy.
Given that my car needs to be fully repainted anyway and I’m handy with a welder I went to town modifying the chassis. Porsche outlines how to seam or stitch weld the RS 964 and 993 in the workshop manual, so I took those instructions and applied them to my chassis. Not only did I weld the seams, but I measured the torsional rigidity before and after to verify that the “Juice is Worth the Squeeze”. Spoiler alert: I measured and 18% increase and only welded the trunk area so far!
Rear Coilover Gussets and Plates
I also added some custom coil over gussets in the rear. Instead of going with 3/16″ heavy plate, I created a 3D shape to get equal strength with less weight. I also had a lot of fun creating speed holes in these 14Ga gussets for extra style points and maybe some extra strength too.
In addition to seam welding the trunk area, I also fabricated some weld in front strut tower braces that will support an aluminum strut bar tieing the left and right towers together. These braces also proudly wear speed holes to match the rear towers. I spent some time on a metal lathe to make the dimple tools. As usual a simple machine operation proved to more difficult and I had to improvise again.
Seam Welding Porsche 911 Trunk Area
The seam welding is simple in principle, but the welding itself is not that easy. As much as I would like to lay down beautiful TIG beads in the front trunk area, the metal just isn’t clean enough. In fact its not clean enough for MIG welding either. The sandwiched seam is loaded with seam sealer, paint and primer, so its impossible to clean properly. The only technique that works is to turn up the welder heat and blast it without melting through. I set up an exhaust fan, but I really wish I had a vented mask because I spent a lot of time outside just waiting for the smoke to settle. Its a nasty job to say the least. Someone told me that its a $2000 job to have a pro do it even on a stripped out a shell. I think that sounds about right, but I didn’t have 20 hours in it. I did it in about 6 hours. $325 an hour? I’ll take it.
I did have headache that afternoon though, which isn’t good and I was wearing a mask.
Torsional Rigidity Improvement Measurement
Many people were interested in my simple measurement method of torsional rigidity. The method consists of me sitting a bar that protrudes 1.5 meters to the side of the car and is bolted to the front suspension mounts. I setup a dial indicator and a camera to measure the downward deflection of the passenger side as I sat on it with all my weight. After welding the trunk area I measeured a 15% reduction in deflection and calculated an 18 percent increase in torsional rigidity. The method wasn’t the most accurate, but anything over 10 percent is icing on the cake in my book.
I hope these modifications will pay off in the long run because now is the time to them while I have access.
Below are the links to the videos highlighting all the work so you too can DIY!