By Barry Brisco
Headrests were a 356 factory option. The mounting brackets attached high up on the back of the seat backs and were secured with sheet metal screws: a rather flimsy attachment system which tends to loosen over time, but of course they are "headrests" for comfort on long drives, not modern head restraints that are designed to prevent neck injuries that may occur in an accident.
Obviously 356 seats offer absolutely no protection against whiplash (neck hyperextension) injury, which some studies estimate occurs in more than one quarter of automobile accidents. The stock seat backs are simply too low, though typical of 50's and 60's cars.
The lack of any head restraint system in my 356 has always been a concern to me: I think it is the most serious safety deficiency now that I have 3-point seat belts installed. But I didn't think the factory headrest installation technique offered any significant safety factor, so I never gave much thought to adding them to my car.
This photo shows the top of a 356 seat back frame and the location of the "tabs" that need to be drilled for the headrest mounting brackets to attach to. These have already been drilled.
Recently a 356 friend had 'captive' nuts welded to his seat frames to make a more secure headrest mounting system. The downside of that approach is that you have to remove some of the seat back upholstery to access the inside surface of the frame to do the welding. I asked Alan Klingen at The Stable in San Francisco if he could do that in my car. He proposed a different but equally secure approach, which is described below.
After removing the seat backs from the bases, and without taking the seat covers off, Alan felt around for the metal part of the upper frame where the headrests attach. The holes for the attaching screws have to be drilled. After measuring carefully, Alan used a special drill bit that would not "walk" and a drilled two pairs of holes. If the seat cover is vinyl it is a bit riskier to drill through as the drill may catch on the vinyl. My seats are leather covered and leather is easier to drill through without tearing it.
He then inserted a "Rivnut" into each hole. These are available from many suppliers. He buys his from MMC in New York. They sell them in metric sizes, Alan used the 5mm size on my seats. Here's a close up image of a Rivnut:
There is a special tool to place the Rivnuts into the holes.
The result is holes that you can thread a 5mm grade 8 bolt into. This means a pretty solid mount for the headrests compared to the factory method.
I have no illusion that this type of mounting system converts a 356 headrest into anything like a modern head restraint. But I think it is a significant improvement over the way the factory did it, and provides a measure of protection against whiplash if I am rear-ended compared to the absolutely zero protection of the stock 356 seat.
Obviously the 5mm bolts do not look the same as the chrome-plated screws the factory used. I am willing to make that trade-off for safety!