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ivwshane
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PostPosted: Tue May 19, 2020 8:57 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

One tip I forgot to mention was that a really good tool for widening the crimped tin (before you paint or media blast), is to use an old chisel to get it in the groove and pry it up. A small chisel is good for the areas that bend where as the larger chisel was useful on the longer flat spots.

As far as the insulation staying in place, I donít think it will be an issue because when you put the halves together it puts pressure on the heat shield and will hold them in place.
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PostPosted: Tue May 19, 2020 7:48 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

asiab3 wrote:
I think any bare blasted metal needs to be protected from corrosion. I've never taken a T4 exchanger apart, but if it were my car I would absolutely use VHT Flame-Proof roof stuff on the pipes if you are committed to the DIY route. It's going to smell for the first few trips, so keep the heater off until the smell goes away.

Since you have them apart, you have the luxury of using the 2000į paint on the headers and 500į paint on the outer skins. The outer shell of most heat exchangers don't usually get hot enough to fully bake the Flame-Proof 2000į stuff.

Unless they slid off with no drama, do a test fit of the manifolds on your heads to avoid having to tweak them with fresh shiny paint. (This goes for tin as well if you plan on refreshing that too, because blasting can warp the metal slightly.)

I look forward to learning what other people did with the insulation.
Robbie


Thanks, Robbie! I kinda thought that was going to be the case. So, yeah, I will prep them to paint (just the tubes not the fins). I used the Flame-Proof 2000į on the shells and I think I will use the same for the pipes. I am going to have to arrange for the family to be out of the house again for the stinky 3 hour process of curing the paint.
I was doing a test fit of one of the exchangers a few nights ago, trying to put it all back together to see how they will fit, but it was late and I was getting frustrated, so I shelved it for a new day. I need to finish painting the pipes now, too, anyway. I am concerned with the tin fitting back together and keeping the new insulation in place.


ivwshane wrote:
I have a 77 so my approach may not be universal.

But I powder coated the pipes and flanges with high temp powder, leaving the fins media blasted bare aluminum.

I shaped the heat shield to match the original heat shields that were two separate pieces.

Because the 77 uses multiple pieces instead of just one like the OPís I media blasted all the pipes and powder coated them with the high temp powder. I then used the heat shield and buttons to make a cover for the f-pipes and I decided to wrap the after burner pipes. My hope is that the powder coating will protect the pipes from any rust/moisture that the exhaust wrap might collect.

Eventually I want to try and replicate the original tins (I have my originals) but that wonít be for a while.

As far as putting things back together. You definitely want to have the channel opened wide to give you plenty of room to squeeze things together. The tool I used do clamp the two halves together was a hand seamer like this:

https://www.homedepot.com/p/Wiss-3-1-4-in-Hand-Seamer-WS3N/301293863

Thanks, ivwshane! I saw that crimping tool in one of the other threads that you were a part of and made a mental note of needing to get it. It seems like it will be crucial for this job once I get there.


Sorry no photos today. No progress today. I am really bummed to not be driving my bus in this great weather. But the new muffler arrives on Friday. Looking forward to that!
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PostPosted: Mon May 18, 2020 6:50 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

I have a 77 so my approach may not be universal.

But I powder coated the pipes and flanges with high temp powder, leaving the fins media blasted bare aluminum.

I shaped the heat shield to match the original heat shields that were two separate pieces.

Because the 77 uses multiple pieces instead of just one like the OPís I media blasted all the pipes and powder coated them with the high temp powder. I then used the heat shield and buttons to make a cover for the f-pipes and I decided to wrap the after burner pipes. My hope is that the powder coating will protect the pipes from any rust/moisture that the exhaust wrap might collect.

Eventually I want to try and replicate the original tins (I have my originals) but that wonít be for a while.

As far as putting things back together. You definitely want to have the channel opened wide to give you plenty of room to squeeze things together. The tool I used do clamp the two halves together was a hand seamer like this:

https://www.homedepot.com/p/Wiss-3-1-4-in-Hand-Seamer-WS3N/301293863
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PostPosted: Mon May 18, 2020 2:19 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

I think any bare blasted metal needs to be protected from corrosion. I've never taken a T4 exchanger apart, but if it were my car I would absolutely use VHT Flame-Proof roof stuff on the pipes if you are committed to the DIY route. It's going to smell for the first few trips, so keep the heater off until the smell goes away.

Since you have them apart, you have the luxury of using the 2000į paint on the headers and 500į paint on the outer skins. The outer shell of most heat exchangers don't usually get hot enough to fully bake the Flame-Proof 2000į stuff.

Unless they slid off with no drama, do a test fit of the manifolds on your heads to avoid having to tweak them with fresh shiny paint. (This goes for tin as well if you plan on refreshing that too, because blasting can warp the metal slightly.)

I look forward to learning what other people did with the insulation.
Robbie
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PostPosted: Mon May 18, 2020 8:26 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

asiab3 wrote:
Ha! I like the bolted end cap solution.

The pipes are indeed straight through, which is why your Dremel-ministering to any flashings at the joints is appreciated. Go ahead and snake whatever won't get stuck through there, but then again they will be black on the inside after a few minutes of running.

Do your best to avoid fingerprints on the metal before painting. I use NEW rubber gloves to handle blasted parts for final cleaning before paint. Like Steve said, most blast media has special clean-up steps. What are you using?

Robbie


Thanks, Robbie! The end caps seem to have worked well.

I used a 2 stage blast with glass media. It shined up well. I am wondering if I need to paint the exchanger's tubes at all. I guess I'm getting lazy, or maybe just frustrated with not being able to take my bus out for a ride. I want to get the engine back in!

I did some dry-fitting of the new insulation, too. question for the folks who've used this insulation: did you try to wrap the whole exchanger with one piece of insulation (cutting holes for the pipes) or did you install it in two pieces like the original asbestos insulation was installed???

It is going to be a pain getting these back together and crimping the edges. In retrospect, I wish I would have completely uncrimped all of the edges before I prepped & painted the shells. After uncrimping the edges now, I can see that there are large portions in the inside channel of the crimped edges that are not cleaned and painted. oops.

Here are some more pics of my progress from last night while my 1yr old baby boy slept.


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PostPosted: Sat May 16, 2020 11:46 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

Ha! I like the bolted end cap solution.

The pipes are indeed straight through, which is why your Dremel-ministering to any flashings at the joints is appreciated. Go ahead and snake whatever won't get stuck through there, but then again they will be black on the inside after a few minutes of running.

Do your best to avoid fingerprints on the metal before painting. I use NEW rubber gloves to handle blasted parts for final cleaning before paint. Like Steve said, most blast media has special clean-up steps. What are you using?

Robbie
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PostPosted: Sat May 16, 2020 11:05 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

asiab3 wrote:
I avoid blasting the insides of exhaust pipes anywhere near the exhaust ports. "Reversion" is the tiny bit of exhaust that is sucked into the combustion chamber with every intake stroke. Because the valves aren't magical devices that open and close instantly, there is always a TINY bit of overlap between strokes on a 4-stroke engine. (This is also why copper exhaust ring leaks can be a tiny vacuum leak source.) I do not like blast media in my combustion chambers, so I don't blast the insides of any exhaust components that attach to the head. Muffler? Sure, but no go on the inside of the header pipes for my engines.

I suspect a long freeway drive on a well-tuned engine should burn out any meaningful carbon deposits from those pipes.
Robbie


Thank you Robbie! I haven't heard of "Reversion", but that makes sense to me now. I assumed that the exhaust ports entirely went one way, but I can see how debris could be sucked back into the head. I definitely do not want sandblast media in my combustion chamber.

SGKent wrote:
just as an FYI, blast media, expecially minerals like glass or garnet etc, create a static charge that holds some of the material to the metal. The only way to get all of it out is to use a mixture of water and wetting agent that nullifies the charges and washes away the particles. That is why machine shops wash the things they glass bead. Then immediately hit it with clean dry air to blast anything else out and dry the metal to stop flash rust. Any media that gets into the outer shell will end up inside the bus eventually. Media on the inside of the pipes can be washed out with the soapy water under pressure, then air as I mentioned.


Thanks, SGKent! I have blocked the ports as best I can and I am going to sandblast carefully. After blasting, I will clean the exchangers as best as I can and then let the exchangers sit in the parts washer overnight again to hopefully nullify the charges and wash away any remaining particles that may be present.

Another question: On the exchanger, are the pipes from the head through the exchanger clear to the muffler? Could you snake a pipe cleaner through? are there fins or blockages of some kind on the inside of those pipes, or are they just pipes? (I guess I could just peek in there with a flashlight, but I've plugged them up now for sandblasting)

Here are some pics of my progress. I've blocked the ports to the exhaust with masking tape first, then bolted a piece of cardboard with wide washers to the exhaust side. On the ports to the head, I cut cardboard plugs that fit exactly in the ports from a thick piece of cardboard. I left a wider (thinner) flange on the cardboard. So most of the thickness of the cardboard is inset into the port while the thinner flange sits on the edge (like an upside down straw boater hat). Then I taped around the edge of the port to keep the cardboard down. I am not going to get too crazy with the sandblasting, so I think this will do just fine.

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PostPosted: Sat May 16, 2020 11:47 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

just as an FYI, blast media, expecially minerals like glass or garnet etc, create a static charge that holds some of the material to the metal. The only way to get all of it out is to use a mixture of water and wetting agent that nullifies the charges and washes away the particles. That is why machine shops wash the things they glass bead. Then immediately hit it with clean dry air to blast anything else out and dry the metal to stop flash rust. Any media that gets into the outer shell will end up inside the bus eventually. Media on the inside of the pipes can be washed out with the soapy water under pressure, then air as I mentioned.
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PostPosted: Sat May 16, 2020 11:34 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

I avoid blasting the insides of exhaust pipes anywhere near the exhaust ports. "Reversion" is the tiny bit of exhaust that is sucked into the combustion chamber with every intake stroke. Because the valves aren't magical devices that open and close instantly, there is always a TINY bit of overlap between strokes on a 4-stroke engine. (This is also why copper exhaust ring leaks can be a tiny vacuum leak source.) I do not like blast media in my combustion chambers, so I don't blast the insides of any exhaust components that attach to the head. Muffler? Sure, but no go on the inside of the header pipes for my engines.

I suspect a long freeway drive on a well-tuned engine should burn out any meaningful carbon deposits from those pipes.
Robbie
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PostPosted: Sat May 16, 2020 11:16 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

BusBerd wrote:
ivwshane wrote:
My heat exchangers are the later style and I didnít blast the inside because it was super rough unlike my other exhaust pipes so I couldnít be sure I was going to be able to remove all the media.

Looking good so far though!


Thanks!

Do you know what the danger is of having a little stray media left over in the heat exchangers?


it will end up inside the bus and possibly in your and your passenger's lungs. Do your best to clean out the exchangers and tubes.
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PostPosted: Sat May 16, 2020 10:46 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

ivwshane wrote:
My heat exchangers are the later style and I didnít blast the inside because it was super rough unlike my other exhaust pipes so I couldnít be sure I was going to be able to remove all the media.

Looking good so far though!


Thanks!

Do you know what the danger is of having a little stray media left over in the heat exchangers?
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PostPosted: Sat May 16, 2020 10:08 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

My heat exchangers are the later style and I didnít blast the inside because it was super rough unlike my other exhaust pipes so I couldnít be sure I was going to be able to remove all the media.

Looking good so far though!
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PostPosted: Sat May 16, 2020 8:30 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

I have finished sandblasting the rest of the shell of each of the exchangers. I painted them as well with high heat paint.

I returned the thicker insulate and purchased the thinner one that was suggested above. (Pic below)

Now I am turning my efforts to cleaning the actual exchanger. I would like to sandblast the exchanger. I read on samba on one of the threads that it is suggested to plug the ports of the exchanger before sandblasting and I am wondering why. If media gets inside the exchanger can it not just be blown out? I want to clean out as much of the carbon deposits as possible on the inside of the exchanger. I soaked them in the parts washer overnight, but noticed very little difference. What is the best way to clean out the inside of the exchanger? (I do plan to Dremel the the edges of the muffler/exchanger ports, but that will only reach a little way inside.)

Thank you for your help!

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PostPosted: Mon May 11, 2020 8:17 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

The one I posted does not have a rigid backing but instead is backed by foil. I donít think sagging will be an issue nor will you need any adhesive to keep it in place.

A rigid metal back using the mesh fiber of the one I linked to would be ideal but Iíve never seen anything like it.
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PostPosted: Mon May 11, 2020 7:50 am    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

ivwshane wrote:
I donít think the breaking down of the metal facing from heat will be an issue as I used a heat source that is way above the backingís rating. What I gained from my informal experiment was that the heat was better deflected (meaning the outside of the heat exchanger was cooler) with the foil facing out.

However there was one more benefit to having the foil facing out that I forgot about. As you may have noticed, your heat exchanger was soaked in oil and I figured oil soaking would be minimized and maybe even burn off if it fell on the foil instead of getting soaked in the fibers.

That being said, itís why I believe the other heat shield I posted would be a better match, not only is it thin like the original but itís composed of a basket weave type fiber which may not soak up as much oil.

Thanks for the reply. The more I think about this, the more I think that I need to return the heatshield that I have and find a thinner one. I think you are right. it is going to cause much more trouble than it is worth.

I looked briefly at the link of the one that you've purchased (and I will look at it again more in depth), but can you tell me if it has the same metal backing that is slightly rigid? Did you have issues forming it to the exchanger shell? Did you need to use anything to keep it securely against the tin so that it doesn't collapse in over time(adhesives seem problematic)?

SGKent wrote:
Just as an FYI from older threads here on TheSamba. If the air flow thru the heater boxes is blocked the aluminum fins will melt. That means they are getting a lot hotter than 700F. They always have air flowing thru them, whether it is dumping or being used in the cabin that cools them down. The late system that Richard Atwell took readings from is covered in a metal plating on both the U tubes and F pipes. Inside is the same material like you found in the heat shields. Exterior temps will read lower than what the inside is experiencing. Aluminum melts at 1220 F so if the heat exchangers melt aluminum fins with the air cut off they are getting to at least 1220 F.

good point. I was wondering if the collection of heat by a restricted airflow would spike the heat higher than the heatshield is rated. I hadn't come across any old threads addressing this. I will try to search again using different terms. Thanks!

ivwshane wrote:
I was using map gas as my heat source...:p

But you do raise a good point. If the air is restricted a little, is it enough to melt the aluminum? I hope I donít find out the hard way.

Ditto.


Thanks, gentlemen! I am going to return this heatshield and research the one posted by ivwshane: https://www.amazon.com/Temperature-Header-Exhaust-...asin_image

I am also going to look for its equivalent on this site: https://www.heatshieldproducts.com

Once again, much appreciated!
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PostPosted: Sun May 10, 2020 9:02 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

I was using map gas as my heat source...:p

But you do raise a good point. If the air is restricted a little, is it enough to melt the aluminum? I hope I donít find out the hard way.
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PostPosted: Sun May 10, 2020 8:26 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

Just as an FYI from older threads here on TheSamba. If the air flow thru the heater boxes is blocked the aluminum fins will melt. That means they are getting a lot hotter than 700F. They always have air flowing thru them, whether it is dumping or being used in the cabin that cools them down. The late system that Richard Atwell took readings from is covered in a metal plating on both the U tubes and F pipes. Inside is the same material like you found in the heat shields. Exterior temps will read lower than what the inside is experiencing. Aluminum melts at 1220 F so if the heat exchangers melt aluminum fins with the air cut off they are getting to at least 1220 F.
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PostPosted: Sun May 10, 2020 8:03 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

I donít think the breaking down of the metal facing from heat will be an issue as I used a heat source that is way above the backingís rating. What I gained from my informal experiment was that the heat was better deflected (meaning the outside of the heat exchanger was cooler) with the foil facing out.

However there was one more benefit to having the foil facing out that I forgot about. As you may have noticed, your heat exchanger was soaked in oil and I figured oil soaking would be minimized and maybe even burn off if it fell on the foil instead of getting soaked in the fibers.

That being said, itís why I believe the other heat shield I posted would be a better match, not only is it thin like the original but itís composed of a basket weave type fiber which may not soak up as much oil.
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PostPosted: Sun May 10, 2020 6:07 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

ivwshane wrote:
While it may seem to make more sense by having the metal side against the heat pipe but my tests showed that the metal doesnít stand up to the heat like the fiber does. It also didnít deflect as much heat when having it that way vs the heat contacting the fiber side firs.


That is interesting. What test did you do where the metal didn't stand up? How much heat did the metal stand before it broke down? The insulant is rated for "Continuous operating temperature of 1800 degree Fahrenheit, 2200 degree Fahrenheit intermittent". I assume that means with the metal side out. All of the applications I've seen is indeed, as you've mentioned, with the metal side out. But, according to ratwell's site (with a slightly different exchanger) the hottest it gets is 700 degrees Fahrenheit coming off the head near the exhaust ports, less than half the temp that the insulate is rated for with "continuous operating" temps. So, I wonder, even if it does not perform at its peak with the metal side on the exchanger fins, would it perform well enough for the max 700 degree temps of the heat exchanger? It just seems like the fiber insulant would be better secured being sandwiched between the shell of the exchanger and the metal facing that is already on the fiber, rather than having the metal facing on the fiber butting up to the shell and then the fiber side open to, on, and in-between the fins.

If my original thought is NOT the placement and it needs to have the fiber side facing the heat source, then what can I use to keep the fibers from obstructing airflow between the fins?

FYI here is the website for Heatshield: https://www.heatshieldproducts.com/heatshield-101

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here are some pics of the exchanger where I tried to show how far the fibers could come down between the fins to obstruct airflow. I also took a pic of it upside down on the exchanger, which is how I thought I could install it. Then I took pics noting the fitting of the original asbestos insulant.
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PostPosted: Sun May 10, 2020 4:10 pm    Post subject: Re: cleaning heat exchangers 72-74 Reply with quote

While it may seem to make more sense by having the metal side against the heat pipe but my tests showed that the metal doesnít stand up to the heat like the fiber does. It also didnít deflect as much heat when having it that way vs the heat pipe contacting the fiber side.
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