Hi gents.

having to replace the front poly original bumper on my 76 as it had started to break and split up. Came off O.K. There is a rusty metal band that attaches at the top and sides and a thin metal band across the bottom.

I have a new fibreglass replacement bumper but no instructions came with it. Do I take this rusty metal bands off to fit the new fibreglass one. Any diagrams or pictures showing the fitting method would be greatly appreciated.

Oh! Is there any material, paint etc that keeps rust at bay for a number of years.

Jamie

 

Those rusty metal bands are the old bumper retainers, they need to come off, nuts accessed from behind.

They can be used with a little work to fit the new fiberglass bumper, but the "t" bolts from any supplier are probably easier.

For rust prevention, I like rust-converting primer (ectend, rust-fix...) others like POR-15.

Steve

 

The rusty metal band is the retainer that held your original bumper on.
You will need to take that off by removing the nuts on the back side. The metal band on the bottom won't be needed with your fiberglass replacement, you will simply mount the bottom of the bumper directly to the lower valance.

You will need to make a decision whether to keep your original crash
reinforcements in place or remove them, because the fiberglass bumper will not fit over them without modifying the center rubber cushion and the honeycomb. I recommend keeping them because in the event of a minor impact, the reinforcement will protect the body since the reinforcements are attached to the frame. The bumper will break regardless, but if you eliminate the reinforcements, an impact will spread into the body panels and cause more damage.

Let's say you decide to keep the reinforcements, here's the basic procedure that I use:
Once you get the old retainers off, Cover the body with paint grade masking tape to protect the paint from damage.



Inspect the fit of the new bumper against the body (don't use fasteners or drill holes until the end) it likely won't fit due to interference with the honeycomb and center rubber reinforcement. If there is interference, start by trimming both sides and the tops of each bumper guard. Use a angle grinder with a grinding disc and trim a little bit of material of at a time and test fit the bumper. I rub children's sidewalk chalk on the inside of the fiberglass cover each time I test fit. The chalk will leave marks on the rubber parts wherever the fiberglass cover contacts it. These are the areas on the center reinforcement will need to be trimmed away. You don't want anything rubbing or chafing the inside of the fiberglass cover. No doubt you will place the cover on and off the car a 100 times to get it to fit correctly

Once the bumper fits over the guards without interference, you need to trim the honeycomb like the pic below. Using the angle grinder, cut the front corners at a 45 degree angle and remove a little off the top edges as well. Again, use the chalk to indicate interference areas.



Once the honeycomb no longer interferes with the fit you can start fitting the cover to the body. Make note of how the sides of the cover align with the forward edges of the fenders and how it fits in the center between the headlights. Don't be surprised if there are gaps. Gaps will be very common on '75 & later front ends such as the Toledo Pro Flex type shown below:




In the above photos, you will notice that the contours between the
headlights do not match and there are gaps at both ends to the fenders. This is where fitting is critical because if you were to tighten the ends of this bumper in place as it is, the center would bow or buckle upward due to the interference in the center. The fit you have will determine where you start sanding.

In this case, block sanding the center of the cover to start (area between the headlights) will move the bumper back a little and reduce the fender gap. Sand straight and very carefully with a hard block a little at a time (keep fitting) and stop sanding when you hit fiberglass. The gel coat is quite thick. Use a round wood dowel wrapped in sandpaper to sand the round areas until they match the body.

ACI standard fiberglass bumper:


Use masking tape to hold the cover in place while you inspect the fit. The idea is to sand the gel coat in trouble areas until you achieve the best fit across the front even if it doesn't look good yet. Then you can proceed with filler on the back edge of the cover to fill the remaining gaps. Generally the gaps do not exceed 1/8" so I use Vette Fill for this. One trick is to mold the cover to the front edge of the body using Vette Fill and Saran Wrap. The Saran Wrap will protect the paint on the body and the Vette Fill won't stick to it. Cover the front body edge with Saran Wrap held in place with masking tape. Sand the gel coat off the back edge of the bumper cover where the filler is needed. Working in 2' lengths or less apply filler to the back edge of the bumper cover and press and align the bumper onto the body and tape it in place until the filler dries. The filler will mimic the shape of the body so that the gap matches and also when you tighten the cover to the body, the cover won't flex. You may have to fill a couple times to get all the air pockets. Once you get it all sanded you can drill the holes and test mount it with the studs.

 

Many thanks gents, especially to Al who took the time and trouble to post the info up. Looks like it's a lot of painstaking effort to get it to fit but will be worth it once fitted.

Jamie.