Heat Box - straightening out fiberglass?

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Dusterdenovo

Dusterdenovo

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I'm now in the middle of rebuilding my heat box and I notice that the front of the passenger side fresh air box is caved in more than 1/4" - looks like the support rod was torqued up pretty tight and the strain on the bracket has made the door - side of the box quite concave.

I'm wondering if gently 'warming up' the fiberglass with a hair dryer or very carefully with a heat gun would soften it up enough to flatten it out? Don't want to try this for fear of it turning to dust or something before running it past FABO.

Your thoughts are welcomed, as always.

Thanks, Larry
 

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Perhaps pop riveting a small (1/4 x 1/4") length of angle alum inside the box,, outta sight, in a manner to support/straighten the box..
 
For sure, to straighten it out now, and also prevent it from just happening again.

Will discover how cooperative 42 year old fiberglass can be. Or not.
 
The support rod there has a predetermined thread length. It must compress a seal to the cowl but cant be over tightened. Given its location, I really don't think the rod could warp the fiberglass even over a long period. The seal fails too so...
If the box is prone to bowing, the door opening is the weakest side.
I'll bet my quarter that the box has always had about the same amount of bow there.
 
Are you thinking that is just a quality thing? I could see that.

The door closes with a bit of a gap along the top, even though I never noticed this 'problem' in the last 6 years of driving the car. But now that it's sitting on the workbench......

I wonder if anyone out there has the same issue with their heatboxes?
 
I don't know that anyone else has looked at this so closely. I certainly haven't.
 
RedFish said:
I don't know that anyone else has looked at this so closely. I certainly haven't.
Click to expand...

LOL i was just going to say...that would be going right back in my car exactly the way it is!

If you hear some kind of whistle or something from the little gap, i'd put a piece of weatherstripping from home depot on the back of the door and call it a day :p
 
RedFish said:
I don't know that anyone else has looked at this so closely. I certainly haven't.
Click to expand...

I have. (looked it over that close.)
The core neeeded replaced so when I pulled it I replaced all the foam seals on the doors inside and out, repaired the front of the box where the Jbolt pulled a hole in it, insulated around all the tubing exposed between the core and the firewall, lubricated all the hinge points, then painted it all and put it back with new defroster hoses.

I agree with the strut idea inside the box, as They are not very forgiving with heat
, and may in fact crack when pushed back out.

I think the combination of a heat gun and a section of flat 1x1/8 aluminum gently inserted and rivited or glued in place would be a really good idea.

15 minute Locktite (JB weld type stuff) works extremely well on that composite glass material if you need to do anything like that for any reason.
 
Trailbeast I'm in the middle of doing the same job with my heat box that you described. After listening to the feedback I'm now thinking that the cure could end up worse than the disease with this warped fiberglass. I did only notice it once it was all on the workbench so I may just go with the extra piece of foam tape.

I'm thinking of painting the heat box with Satin clear coat to freshen it up a bit, so if I crack it worse it would look crummy with a big epoxy repair on it and I'd have to go with satin black or something.

If this all sounds anal, it probably is but it turns out that nothing is too good for my mistress....

One thing, I'll mention, I just got my hands on my Detroit Muscle Heat Box rebuild kit yesterday. At first glance, it looks pretty bang on for fit and materials. Anxious to get this puppy back together.
 
If the heater box has a crack in it, could gorilla glue fix it or should I search for a new one. It's 50 years old so I guess I shouldn't expect it to be flawless. It is a large crack, Hope to remove the dash today and check more on the box in the morning. I have the rebuild kit for it. Should you just clean these really well, or paint them.
 
My heater box is the same way, I did not notice it until I replaced the heater core.
 
I don't think it is typical fiberglass, more like fiber-reinforced plastic. Anyway, I repaired some small gaps w/ plastic epoxy and drywall mesh. The epoxy is the 2-tube type ($6).
 
I used my wife's blowdryer (just this side of a heat gun), and heated up the problem area a couple of times, straightening it with bar clamps against a steel plate a little more each time. The fiberglass or whatever it is did actually soften up and move. It stayed straighter each time it cooled after I did the heat up/clamp process to the point where it is almost but not completely 'good as new'. A tiny crack formed on the lip of the door but I used plastic epoxy on it and it's staying put. I also fitted a piece of aluminum angle in the box and riveted it to the support bracket to prevent the box from distorting again.

That plastic epoxy is great stuff - drilling out the rivets on the vent door caused some ugly holes that I just filled in with epoxy and redrilled neat new holes.

A light sand and a couple of coats of satin clear and the heat box looks great. As mentioned earlier in this thread, the Detroit Muscle rebuild kit was perfect for the job.

I'm putting courtesy lights under the dash, so all this work will look really slick under there.

Final assembly of the heat box this week.
 

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Tadams said:
If the heater box has a crack in it, could gorilla glue fix it or should I search for a new one. It's 50 years old so I guess I shouldn't expect it to be flawless. It is a large crack, Hope to remove the dash today and check more on the box in the morning. I have the rebuild kit for it. Should you just clean these really well, or paint them.
Click to expand...

I pressure washed fiberglass parts, gave them a light sand and 2 coats of satin clear. Glass beaded the metal blower plate, flaps and lever pivot shafts and cleared them as well. Fixed a few little repairs with plastic epoxy. with a light sanding of the surfaces to bond, it sticks like steel.

Turned out great. Will post a picture of it all back together this week.
 
Good job Buckwheat. That came out nice.
 
100_5601_zpslsnvt7fm.jpg


The left inside corner

I have cut a slice in it> to let it open up
placed a piece of angle iron on the outside
heat the box with a heat gun
place a short piece on the inside, clamped together with "C" clamps

reheat a few times

then fill the gap, in the corner with J B weld
 
Use some rtv to build up the gaps let it harden some tape up the door and close it come back a few days later pull the tape off the rtv... Straighten the box all you want once it gets a few heat cycles it warps back or cracks.... $ .50 fix
 
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