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'73T Heat Exchanger Rescue... worth the trouble?

Hi All,

I'm cross-posting this out of my separate thread in the engine rebuilding forum... seems more appropriate here.

Newbie '73T 2.4 MFI Engine Rebuild

I pulled the original heat exchangers, and had them blasted with the intent of painting or coating and re-using them. The blasting revealed quite a bit of pitting, and the repair looks to be well beyond my meager metal working abilities.

Other than the pitting, they're completely intact, and in pretty good shape.

Any opinions on how one might repair something like this? Or is this the obvious kick in the pants needed to get into some new SSIs?

Thanks!


- Jake





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Old 07-02-2018, 04:33 PM
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The pitting looks to have perforated the metal envelopes in quite a few places. I’d look for some SSI (or Dansk now) exchangers instead of spending money on these.
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Old 07-02-2018, 06:30 PM
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I welded some patches on a set iím still running on my car. Iíll eventually get SSIís and regret not getting them when they were cheaper and USA made. But my patches have held up just fine.
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Old 07-02-2018, 08:12 PM
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For your safety, get some SSI's
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Old 07-02-2018, 08:13 PM
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It’s not the holes you can see that are dangerous. If the header pipes inside the heat exchangers are perforated you will have exhaust gas entering the cabin.
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Old 07-02-2018, 08:26 PM
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I recon do a Josh style repair - or get a workshop to do it. Nothing too fancy. Just a bit welded over the top of the rusty bits.
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Old 07-02-2018, 08:30 PM
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Dansk not only makes SSIs but steel heat boxes as well duplicating the original including the street sweeper style of 72/73.
What you have lasted over 40 years when it was driven in any weather, that will never be duplicated in today’s market.
Save nearly half of SSIs pricing and tomorrow what you run won’t make any difference.
Bruce
Old 07-02-2018, 09:14 PM
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Quote:
Originally Posted by timmy2 View Post
Itís not the holes you can see that are dangerous. If the header pipes inside the heat exchangers are perforated you will have exhaust gas entering the cabin.
Easy enough to pressure test if you wanted to.
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Old 07-03-2018, 04:55 AM
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Thanks for the feedback.

@Josh D:
Nice pics. That's exactly the kind of repair I was imagining- just not sure I can pull it off

Quote:
Originally Posted by timmy2 View Post
Itís not the holes you can see that are dangerous. If the header pipes inside the heat exchangers are perforated you will have exhaust gas entering the cabin.
Quote:
Originally Posted by Josh D View Post
Easy enough to pressure test if you wanted to.
I don't have any evidence that the internal header pipes are damaged (though, not sure how I'd know...other than not falling asleep the last time I drove it???). Given the safety concern, a quick pressure test would make a lot of sense! Any suggestions on doing that? I'm picturing some rubber stoppers jammed into the headers, one w a fitting for my air compressor.

Thanks again,

Jake
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Old 07-03-2018, 05:42 AM
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Quote:
Originally Posted by Josh D View Post
Easy enough to pressure test if you wanted to.


Yup.. Savable. I do them for customers all the time.

Pressure test to make sure a good way to double check header integrity
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Old 07-03-2018, 05:54 AM
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slap em back on and drive. Mine were WAAAAY worse then that and gave plenty of heat in Canadian weather deep into December. The actual exhaust is way thicker steel than that so it wont be an issue. Unless its a concours car , and all you want is a bit of heat those will be fine. even just rivet on a patch if its beyond your welding skills with some muffler cement between. I mean really you just want a bit of heat, you will get another 5 years out of those things easy.

just a redneck perspective
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Old 07-03-2018, 06:20 AM
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Good thread. My 82 has stock units and I too would like to upgrade/backdate my exhaust. I looked at a set a few months back and found some nasty corrosion on the pipes, including where three merge to one. There is a repair section available for the straight-ish length from the muffler flange forward, but on the one I looked at, it would not have sufficed.
Assuming the pipes were ok, the welded casing repair shown above looks very sensible...I'd run those with no shame. John in CT.
Old 07-03-2018, 02:09 PM
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I kind of went overboard, but I was enjoying the challenge. Welding metal that thin with a mig was interesting.
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Old 07-03-2018, 02:43 PM
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Quote:
Originally Posted by Josh D View Post
I kind of went overboard, but I was enjoying the challenge. Welding metal that thin with a mig was interesting.
I was wondering about that... what gauge sheet did you use? 22awg?

I'm afraid I'll burn more new holes than I'll fix Still, I might give it a go...

- Jake
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Old 07-03-2018, 03:00 PM
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TIG weld it if you can .. Use 20 ga.
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Old 07-03-2018, 03:14 PM
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I got some parts together to pressure test the headers, just to confirm that they're sound and that the pitting is limited to just the heater boxes. This was a fun and easy project, and it revealed something useful too!

I ordered a "tank valve" and some #8 rubber stoppers from Amazon. My plan was to plug up the headers, and mount the tank valve into one of the plugs so that I could pressurize the system using my normal tire inflator, which has a built in PSI gauge.

Here's the tank valve:



... and mounted in one of the plugs. I got solid plugs and drilled a 1/2" hole in one of them. The tank valve threaded right in:



Then I used some 1/4" hardware through some scrap particle board to block off the exhaust exit. Here's the basic setup:



I couldn't get the particle board to seal, even with some rubber acting as a gasket. The more I cranked down on the bolts, the more it would flex in the middle, creating a gap. Fortunately, I had some scrap 1/8" metal laying around- that did the trick. I used a piece of rubbery toolbox shelf-liner as a makeshift gasket, you can see it sandwiched in there.



Worked great! I'd get a little pressure built up- didn't take much- and one of the plugs would pop and shoot up to the ceiling! I think I could've ended the test here, but I wanted to see if I could build up some more pressure, so I tried to clamp the plugs down into place:



This kinda worked, but I had to keep one hand on the un-clamped plug with the valve in it, otherwise it would shoot out. I could usually get to about 10 PSI before this would happen (but my hands were full so I couldn't get a pic of the gauge reading). Anyway, this header definitely looked good.

Here's the next one:



This one was leaky right off the bat. I thought maybe I had a big problem, but I was able to find the leak, right here in one of the welds:



I could hold my finger over these 2 little holes, and then build up a little pressure. So, I think this one is all good as well- just need to fix that weld a bit.

With that, I'll try to patch the pitted areas on the heater boxes. I may not get very far, but at least I now know that the headers are fine!

Cheers,

- Jake
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Old 07-07-2018, 08:32 PM
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Also, the rubber stoppers came in a 10-pack. I'm only using 3 at a time, so if you want any of the extras, just pay for shipping and they're yours.

Jake
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Old 07-07-2018, 08:35 PM
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You could have just cut out the rusty bits and had a look then welded in your replacement strips....Regards,Michael.
Old 07-09-2018, 10:50 PM
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Good job. John
Old 07-10-2018, 03:29 AM
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Quote:
Originally Posted by donlan View Post
You could have just cut out the rusty bits and had a look then welded in your replacement strips....Regards,Michael.
Yeah, you're probably right- but I wanted to know for sure. This was cheap and easy- plus, I would have never otherwise found the leaky weld on the header outside of the heater box.


Quote:
Originally Posted by jjeffries View Post
Good job. John
Thanks! But it's a bit premature- hold your judgment until after I butcher the sheet metal

- Jake
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Old 07-10-2018, 05:13 AM
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