C3 firewall hood pin repair?

[Steve Wallach]

Anyone have a "NCRS" acceptible repair for the fiberglass hood pin area? This area seems to be commonly damaged and I'm trying to create a "perfect" repair for my 68 Coupe.

The stud plate rivets under this box, and is difficult to get to, but I can rivet the plate to a repair piece and then try to glue the fiberglass back into place, but this will make for a sloppy looking repair. Replacing the entire upper firewall really isn't an option either. (The 68 upper firewall is slightly different than the replacements or even NOS that I have seen)

Any suggestions?

Thanks,

Steve

[Chuck S.]

Re: C3 firewall hood pin repair?

A picture would truly be worth a thousand words in understanding what's needed to make this repair.

Typically, unless fiberglass pieces are missing, the approach would be to remove the bolting plate, taper grind the fractures, and laminate resin and mat over the fractures. To minimize the use of body filler, I usually laminate four or more layers where the books say only three layers. Ideally you would like to be able to laminate resin and mat to both sides of the repair, but in the case where you have no access to the backside, one side will have to do.

Once the repair is cured, use 80 grit paper on a block, maybe even on a grinder if you're careful, to sand the repair to contour. Locate the bolting plate, drill the holes and rivet the bolting plate in place.

[Steve Wallach]

Re: C3 firewall hood pin repair?

Hi Chuck,

The fiberglass is missing, but I have pieces from another firewall. The issue becomes riveting the plate in place before I glue it all into place. If I have to add resin, the rivets are then too low...
It's somewhat of a difficult repair.
If I can find a good firewall piece, I would be able to slide it from the front over the existing damaged piece and glue it over and on the old / damaged piece and blend it at the back of the firewall. The hard part is finding the good piece. I guess it was common for this area to become damaged.

Thanks for the suggestions,

Steve

[Dick W.]

Re: C3 firewall hood pin repair?

Steve I do not know of a Vette salvage yard in CA, but a good place to try on the other coast would be Cannons Corvette http://www.cannons-corvettes.com

[Chuck S.]

Re: C3 firewall hood pin repair?

OK...I just went out to take a look at my full scale training model. I see what you're up against now...you need to replace the entire "box" on the driver side where the hood latch bolts.

This is what I would do: First, find a donor piece for the box. As Dickie says, junk yards are a possibility, but unless the body is a total loss, they may be reluctant to chop up the firewall to give you a donor repair piece. You might also try The Corvette Image...they can provide a repair piece for most panels if you define the boundries you want. In this case, defining the boundries looks pretty simple.

I would remove the "box" at the bonds on the sides and at the back. You can try wedging the joint to break away the box flange, but be careful...the firewall fiberglass may break rather than the bonding adhesive. If you destroy the box flanges getting it off, it's no big deal.

In the front, I would make a straight saw cut across the firewall face where the brake booster or master cylinder bolts; the ideal place for the cut is right at the bottom of the side bonded joints. I believe there is a steel reinforcing plate directly behind the power booster...if that's the case, you will have to figure out how to make a neat cut without getting into the reinforcement (setting a cordless circular saw to shallow depth?)

You will probably end up grinding the bond areas to smooth and prep them for the repair piece...be careful to not cut off the rivet heads; the heads of the aluminum rivets holding a steel reinforcement under the dash are directly under the box flanges on both sides.

Do a good trial fit up of the donor repair piece to the open hole. Taper grind the sides of the saw cut joint before bonding the piece into place. With the hood latch bolting plate riveted to the donor piece, I would bond the repair piece in position on the firewall, then laminate resin and mat across the saw cut seam. Finish to contour. If you do good finishing work, once the firewall is blacked out, only your fiberglass bodyman will know for sure.

[Steve Wallach]

Re: C3 firewall hood pin repair?

Hi Chuck,

Sounds about right, except it's the Passenger side I'm repairing, so hopefully a little easier.

Thanks Again, I'll give The Corvette Image a try.

Steve

[Chuck S.]

Re: C3 firewall hood pin repair?

Your passenger side firewall may be different from my 70. It appears all the rivet heads for the stud plate are accessible through the wiper compartment/plenum on my car; not easy to get to, but you only have to back up the head...the top end is the one that is peened. There are, however, no good break points for the repair on the passenger side...a little more pressure on your finishing skill.