72 front bulkhead configuration

[Don K.]

Hello,
This is my first post on the Technical Discussion Board.
A friend of mine is restoring a 1972 big block convertible. My hobby of restoring old fiberglass boats from the fifties, and my experience from glass repairs I did on my 62 Corvette, led him to ask me for some help on the body restoration. The engine, suspension, and driveline have been completed and he has now mounted the body on a stand.
The body is not in the best of condition. It has suffered both front and rear crash damage and the repairs were crudely done.


So the questions are;

Is the metal gusset used on all C3 models?

If so, would it then have a metal gusset?

Any pictures, dimensions, sketches, etc. of this area would be appreciated.
This car is not being restored to a judging level, but the owner wants to do as much as reasonably possible to make it correct.
Thanks.

[Bill C.]

Re: 72 front bulkhead configuration

AC hoses go through an area that is passenger side, way up top by where the core support bolts to the fiberglass (see old photo of car before resto).

As for the mess on the other side ----
someone just hacked out part of the fiberglass side and metal side support. You will need to replace the inner glass section and get a new core support side bracket. I will try to get a pic from my car for you.

The holes for the bumper brackets --
they had a rubber flap (like inner fender well covers) stapled to the fiberglass. I think the holes were quickly cut out - but not really sure.

I will try to get pictures for you.

[Bill C.]

Re: 72 front bulkhead configuration

more pics ---



ALSO --
on the second picture where you have labled "AC hose access" -
that may be where the head lamp vacuum hose pass through as well as the foward lamp harness.... not 100% sure on this.

[Don K.]

Re: 72 front bulkhead configuration

Thanks Bill, that gives me a little more idea of what we are up against. The owner had removed all the metal supports, radiator, and associated parts a few years ago when he started the restoration and they are still packed away. It looks like we are going to have to get that stuff out and mock up the whole area to make sure our geometry is right and to identify where we have missing fiberglass.
I still am wondering about that gusset.
Thanks again for the pics!

[Bill C.]

Re: 72 front bulkhead configuration

Mine is a 72 and I do not have that gusset anywhere.

Mine is a April production car - maybe it is a carry-over from 70-71???

Glad the pics could help you out --

If you need any other pictures - be more than happy to take some for you.

[Chuck S.]

Re: 72 front bulkhead configuration

Mine is a 72 and I do not have that gusset anywhere.

Mine is a April production car - maybe it is a carry-over from 70-71???...

No, not from 70 anyway. I'm pretty sure that reinforcing plate is not original. If it is original, then this is for an option I don't know about.

That appears to be a designed bulkhead penetration for a model-specific aftermarket air conditioning system. The refrigerant hoses or tubes may have passed through the driver side bulkhead if the compressor mounting was on the driver side of the engine. Aftermarket retrofits put stuff where there's room, and not necessarily where the factory installed it.

The reinforcing plate is clearly designed for hoses or wires to pass through...note the rolled inner edge. Examine the edges of the fiberglass cut...if it's a retrofit, I would expect those cuts to be rough and ragged or at least very irregular. As Bill says, it could also be irregular if it's a factory hole.

I would patch rather than replace the bulkhead; that bulkhead has a lot of strong, complex bonding joints to the inner fender, outer fender, and lower fascia pan. Repair will be considerably less work, and it will be undetectable if done properly. I can't be sure from the pictures, but if they also butchered the lower fasica panel and the spoiler flange below, I think I remember that being relatively easy to replace.

As Bill says, there is metal reinforcing bracket for the radiator support that rivets to the outside of the inner fender. There is also a flange formed into the bulkhead's radiator support side; if that flange is completely gone, it will probably be easier to just graft in an edge with the flange...forming thin flanges like that out of resin and mat is a giant PITA.

In the 70 AIM, this detail is shown in UPC11/13, Sheet B2. It should be similarly located in the 72 AIM...next to last section before options.

[Rich P.]

Re: 72 front bulkhead configuration

I have seen the pop riveted gusset on later 70-early 80's fenderskirts and NOS replacement skirts that we used to get in body shops back in the early 80's.

Rich

[Chuck S.]

Re: 72 front bulkhead configuration

I have seen the pop riveted gusset on later 70-early 80's fenderskirts and NOS replacement skirts that we used to get in body shops back in the early 80's...

Interesting...later cars must have used the hole for something, and service replacements superceded the earlier design.

Probably the best approach is to use one donor piece to replace all of the radiator support side of the bulkhead from above the reinforcement rivet holes down to just above fascia pan bond by making cuts into the top and bottom of the bumper support hole.

The flange I mentioned earlier ends about 2" above the pan bond, and "angles" back into the bulkhead edge below, which has a little roll in it...about 1/2" radius. That would be a good location to make the bottom cut.

It appears the inner fender is missing now; that will simplify the repair considerably.

[Jack H.]

Re: 72 front bulkhead configuration

A/C equipped cars from this era DID route the refrigeration lines serving the receiver/dryer + condensor through the wheel well. The body cuts were rather crudely made (no real dimensional spec) by assy workers in a hurry to churn jobs out the door.

Consult the AIM (Assy Instruction Manual) under the C-60 (A/C) option in the rear section of the book. You'll find the call-out(s) for the body components that were affected by the addition of A/C.

Also, an issue that MANY restorers and body repair folks miss, is installing the refrigeration hose protective panel to the inner fender in the RH wheel well. Savvy judges will use their fingers or inspect with a mirror/flashlight for the presense of this added fiberglass panel and deduct accordingly for its absense.

The panel or shield was installed to surround/cover the refrigeration hoses routed through the wheel well and protect them from stone-throw and/or road debris that might be kicked up by the front RH wheel while the car was in motion...

[Chuck S.]

Re: 72 front bulkhead configuration

A/C equipped cars from this era DID route the refrigeration lines serving the receiver/dryer + condensor through the wheel well...Also, an issue that MANY restorers and body repair folks miss, is installing the refrigeration hose protective panel to the inner fender in the RH wheel well...

All true, Jack (I have one)...but this "funny hole" and his repair problem is on the driver side.

[Don K.]

Re: 72 front bulkhead configuration

Thanks everyone for all the input.
I am now convinced it's a factory gusset, but as Rich says, probably on a service replacement piece. I spent 40 years working in manufacturing and service engineering and everything about the bracket and rivets says it was done as a factory process. The rolled edges indicate it was stamped with a die and each rivet is compressed to the same shape and height.
As Chuck mentioned, the gusset was shaped to clear the "funny hole" so I have to assume when the gusset was riveted on by the factory the hole was there at the same time. I believe the gusset was probably a response to a cracking problem from one hole to the other.
The owner says the car never had an aftermarket AC that he was aware of so the chances are it is not a hose access hole.
Some of you oldtimers may remember that Themo King (maker of truck/ trailer refrigeration) sold add-on auto AC systems in the late sixties and early seventies. I started with them in 1969 and my first job was to train technicians to install aftermarket AC, and as Chuck said, the hoses could be anywhere. Speed of installation was paramount. Where they went, and how they looked was secondary.
The possibility of this being a service part means it could be a fit-all part and the extra hole has a purpose for an option in some other year.
So, the plan right now is for me to do a better job looking at the AIM. I may have missed something.
We also need to get all our metal parts out and see just we have and don't have.
I think we also need to try to get a look at one or more local (Minneapolis) cars to see just what the correct configuration is.
I really don't think we will have to replace the whole bulkhead. I've gotten pretty good at fabricating quick and dirty molds to make complex patches for boats, and if I can see what is missing I think I can reproduce a decent patch.
Thanks again for the input. You can never get too much info when you have a project like this one!