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Went out to the shop tonight to take some measurements of the exhaust ports on the plenum and defrosters under the dash.
There are two different sizes. One size for both the left ports and one size for the right side ports.
For the right side, I can use a 2x4 scrap as a mold and do noo even have to cut if down. The left side is about a 1/2 longer so I can rip a scrap 2x6 for that mold. I have already ordered some sheets of ABS plastic. I am looking forward to attacking this.

Also, I have some door glass and vent windows on the way from Southwest Packard to replace some broken glass that I have.

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Looking forward to seeing your results.

Since you have so many sharp 90 degree bends both in the middle and on the sides the ABS will need to be quickly placed and formed before the stuff gets too hard to do a good bend yet also held while it completely cools. It will be worse with any little segments resulting from slits needed to avoid tears or wrinkles in the material.

To help the situation you could make two secondary molds for each size out of 1/2" plywood or such. It would need to be slightly larger in width than the pattern side with a gap only on the narrow sides roughly double the thickness of the ABS on each side. Make it so you can place the hot ABS over the actual pattern side and then after starting the bends with your hand gently push the larger mold on top to sort of help form and hold the ABS to the pattern. Once formed you can leave it like that while the ABS cools enough to retain the shape. Gently rounded edges or corners on both sides of the molds will help the ABS form without tearing.

How are you going to join the halves. If you plan to overlap the full sides then making one of the secondary molds slightly wider and adding a thin piece of cardboard or such the same thickness as the ABS to the sides of the pattern mold before forming the second half might provide a kind of slip fit when they are joined.

I found it hard to handle the ABS when hot and you almost need a flat solid metal surface for it to lay on while it heats and then help you carry it to the project so it does not droop. My kitchen oven and an old cookie sheet worked well but your wife may have other ideas so good luck there.

10 years ago last week I brought my 400 home from Memphis TN.
10 years ago this weekend I started this blog.
On the 24th of February, I am retiring after 31 years of working for the US Army as a civilian employee.
With more time on my hand and spring on the way, I may finally get to take the old girl for a ride.

Got some new parts this week and more are on the way.

One of my vent window frames is cracked. I am told that is pretty common.
If I grind off the chrome plating around the crack and repair the pot metal with Muggy Weld, is it necessary to re-chrome the whole part? The repaired area will be inside the door and hidden from view.

It would be cheaper to replace the whole part than get this one re-chromed.

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Muggy weld might work but you might also look thru Riki's 56 Ultra blog somewhere toward the last third. As I recall he did that exact same repair and had issues with the first method he tried. Don't remember if he wound up welding or just making a reinforcing plate to fit the hollow space and screw in.

Don't think it is necessary to rechrome unless the heat being that close to some visible part would travel and discolor..

I test fit the plenum this week so I could mark the hole for the heater core.

Also used the ABS plastic sheets to make one of the ducts for the defroster. I'll do a seperate post on those.

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I made a mold, using 2x4s, as Howard suggested. I put the 2x4s in the oven with the plastic sheets laying across it. With the oven at 325 degrees, it only took 3 or 4 minutes before the sheet was formed to the shape the lumber was setting on. Then I put the top of the mold over it to hold it in place. The first half was left in a little too long and started to warp along the edges, I took the second one out sooner and avoided the warping.
I made some slices along the edge and used then reheated them to shape them into a 90-degree angle. So now I have the two halves.

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I trimmed both halves to the correct length and used rivets to hold them together.
I am not sure if I will use this first one or not. The 2x4 I used to shape it may not be large enough. I made need something just a little larger but I will mess with it some more tomorrow before making the other side.
I am thinking that I will wrap it in the metal duct-work tape seen in the last image.

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Not a bad first effort. By the time you have the second or third made you will be comfortable with the process and can go into business. There are probably others that have falling apart or missing cardboard ducts.

Tape is not a bad idea but wonder how the defrost heat would affect the adhesive over time. I have not tried it but wonder how black ABS plumbing pipe cement would work on the sheets. If it would stick and soften the sheets like it does with pipe you could make a flat side piece. Hopefully the glue would melt the two together to form a hard cover over the segments to hide them and block any air leaks. If it does melt them together you might even cut each side down so a seam forms in the middle with no overlaps then cement everything together with the flat side pieces.

If the end openings are a tad off size on the small side you might be able to make a sort of taper mold the exact size needed or maybe a tad larger and then reheat the plastic and force the end over that to stretch the plastic a tiny bit. Once it hardened again it should be a close fit. If they are too large a layer of felt or thin foam weatherstrip on the outlet opening might take up enough slack.

Either way, I think it will need a screw or two to maintain the connection. Packard used one on the plenum side IIRC but the hard plastic may not have as much friction as the cardboard and might need a second.

Stewart

Why not make it out of stainless. Sheet. Cut the curve

18 Ga for sides

20 Ga for top and bottom.
Easier to bend

Then weld it up..

EDIT.

Could still use the black stuff to retain the heat
Pop rivet it on.