Rear Seat (Lap) Belt Installation

[EmTee]

Background: The subject of this project is installation of rear lap belts in my 1964 Pontiac Grand Prix.  When this car was built front lap belts were not mandated and could be deleted by selecting the proper code on the factory order form.  My car did receive factory-installed front lap belts, however, there are no rear belts.

 

At just 2 years of age, it is already clear that my grandson has inherited ‘the car gene’.  He has scores of Matchbox and Hot Wheels cars as well as larger trucks and ride-on toys.  If it has wheels, he likes it.  He already identifies each family member with the vehicle they drive.  When he comes to visit and I bring him out to my garage he consistently heads directly over to the Pontiac and asks to get in.  Since taking my grandson for ice cream in the GP this summer is predicated on being able to fasten him and his car seat securely to the rear bench, I ordered a pair of new, but original style, lap belts for installation.  The following summarizes the procedure I followed to complete the job.

 

1. The photo below shows the floorpan structure with the rear seat removed.  The problem I was faced with was how to determine where the anchor points should be located.  I did some Internet research, but since my 1967 Riviera has factory-installed rear lap belts, I decided to remove the rear seat bottom from the Buick to see how GM did it.

2. What I determined from my research and by looking at the Riviera installation was that ‘dimples’ in the sheet metal just above where the floorpan joins with the brace that forms the front of the trunk/rear seat back support were possible candidates.  The passenger side outer location is pictured below.

 

3. The spot I chose for the passenger side center location is shown below.

 

 

4. Before making large holes in my car, I decided it would be prudent to drill a small 1/8” pilot hole first so that I could confirm the location from under the car.  I wanted to ensure that I could install all of the hardware, access the nut with a wrench and make sure that there were no cables, brake/fuel lines or other interfering structure.  As seen below, the area was indeed clear and provided a good, flat area surrounding the anchor point.  I did the same for each of the candidate locations.  If I had encountered a problem, the small hole would have provided a reference point to locate a suitable spot.  The small hole could then be plugged with caulking compound.

 

 

5. Below is a picture of the hardware that I installed.

 

 

6. I purchased 7/16” x 1 ¼” Grade 5 bolts and self-locking nuts.  I also purchased a selection of washers, including the largest diameter fender washers that I could find.

 

 

7. I doubled the large fender washers and then included a regular flat washer then the nut.  On the inside, I sandwiched the belt anchor between a pair of flat washers.  So, the schedule is: bolt head/flat washer/belt anchor/flat washer/floorpan/fender washer/fender washer/flat washer/lock nut.

 

 

8. I used black RTV to seal the hole where the bolt passes through.  I also applied a dab to the first fender washer installed against the floorpan.

 

 

9. Here’s the view from under the car with the belt anchor installed and tightened.

 

 

10.  Below is what the installation looks like from inside the car.

 

 

11. This is a shot showing both the inner (left) and outer (right) belt anchors as viewed from under the passenger side looking forward. It is important to space the belt anchors 12 to 15 inches apart – NEVER install the two belt halves using a single anchor point.

 

 

12. Another inside shot showing the inner anchors for the right and left belts.

 

 

13. With the seatback installed, the trick is to get the bottom in place with the belts on top of the seat cushion while keeping them from slipping back and falling under the seat

 

 

14. The finished product, ready for an ice cream run!

 

 

Hopefully others will find this information helpful, as the basic procedure should work on many 50's and 60's classic car.  The belts are available online from multiple sources and I sourced the hardware from a local fastener wholesale outlet.

 

[Larry Schramm]

If you would like to get correct seat belt anchors like this,

 

You can look here:

https://www.summitracing.com/parts/hfm-sbhp?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-autoloc&gclid=CMedusn4wNMCFYW4wAodiQIJJg

 

Or here:

https://www.julianos.com/Installation-Hardware-s/5.htm

Edited April 26, 2017 by Larry Schramm (see edit history)

[DavidAU]

Larry is right.   you have done a great job by installing the seat belts but in the event of a collision the sharp edges of the washers can tear straight through the floor panel. Even double thickness like you have.   

This is why the anchor plates that Larry put up have the edges bent down so if they are subjected to an instant load they will pull the floor panel up but not cut it and allow the seat belt to become free.

[EmTee]

OK, I think I'll swap the washers for a set of those reinforcement plates.  I'll update this thread after I have made the change.  Though unlikely (particularly as infrequently as this car is used), they don't call them 'accidents' for nothing... 

 

Order placed at Summit.

Edited April 26, 2017 by EmTee (see edit history)

[ted sweet]

aren't  the plates designed to welded to the floor?

[Larry Schramm]

I think that they are usually welded to the floorboard for ease of assembly when the vehicle is being built and always having a nut where it is supposed to be.  That way when installing the seat belts at the factory only one person is needed to install the belts.  I do not think welding the plates is a requirement because the ones that I have removed usually have had only a couple of spot/ resistance welded points to retain them in location.

Edited April 29, 2017 by Larry Schramm (see edit history)

[EmTee]

I received the anchor plates that I ordered from Summit.  Hopefully I will have time to install them this weekend.  I thought about drilling a hole in the plate to allow a spot/tack weld, but since my interior is installed I get nervous about hot work.  As an alternative, rather than weld, I'm considering using a self tapping screw through the floorpan into the plate.  That will keep the plate from spinning as I tighten the anchor bolt.

[Larry Schramm]

Let us know how it turns out and post some pictures if you can.

[Spinneyhill]

7 hours ago, EmTee said:

As an alternative, rather than weld, I'm considering using a self tapping screw through the floorpan into the plate.  That will keep the plate from spinning as I tighten the anchor bolt.

 

Drilling another hole will introduce another avenue for rust in the floor unless it is protected.

[EmTee]

I plan to caulk all holes and undercoat the plate from under the car when done.  That said, I don't wash the car with a hose and it doesn't leave the garage if rain is threatening.