You really don’t want to weld this thing in and then have it be wrong.
There’s one last thing to attach to the frame before it is installed in the vehicle.
There is some debate on the internet about whether or not this is a good idea. Some people say that the bolts should not be welded because it adds thermal stress to them, which can make them brittle if they are cooled too quickly.
Barry has been building them like this for a really long time. No one has died yet, or even been seriously injured. While the internet rumors may be true, I’m OK with it.
The existing passenger-side seat mounting was deemed sufficient for a passenger. But I was still switching from 5- to 6-point belts, which meant more holes. Here Barry is taking Tom’s place in drilling holes in the car. Because what is a race car if not a large quantity of metal designed to have holes drilled into it?
It is vitally important not to simply place a nut underneath the eye bolt under the chassis. The metal of a vehicle floor is extremely thin. It is in no way designed to withstand the type of force that would be exerted by the nut pulling up against it from the eye bolt being pulled by the harness.
These FIA/SFI certified backing plates are designed explicitly with the purpose of going underneath the floor and securing belt mounting hardware. The Sabelt ones even have a little threaded hole so that you can prevent the assembly from rotating. Other safety companies make certified fender washers.
DO NOT INSTALL SUB BELTS IN THE FLOOR WITHOUT USING CERTIFIED SANDWICH PLATES.
Your life likely depends on it.