Alternator heat shield advice sought

[dllubin]

I've got a 74 alternator heat shield that I was cleaning up and accidently got a small amount of water on the insulation material (faces exhaust on vertical part of shield).

The insulation that got wet turned into a watery oatmeal-like substance. Not sure how it lasted 44 years without getting wet but there looks like there are the remains of a dark coating in places. Perhaps that was the waterproofing. The insulation was held on by the bendable tabs.

Does anyone have a recommendation for suitable replacement insulation?

Thanks,


Don

 

[Dr.Jeff]

Don, there is a common product that would work great for this. It is some kind of woven glass type of fabric made with a reflective layer on one side and a strong self adhesive on the other. I've used it for lots of applications and it does an amazing job of preventing the heat from transferring past it. Different companies call it various names, and prices are all over the place. Look for a generic one.
Looks like this:

 

[dllubin]

Jeff:

That looks like a good candidate. Do you recall what name(s) it goes by or what type of places sell it? It certainly looks like a lighter alternative to cementing on a firebrick!


Thanks,


Don

 

[Dr.Jeff]

If you want a generic (less expensive) version, try ebay. Otherwise for a brand-name version try one of the big mail order parts houses like Summit or Jegs, etc. I don't recall the proper name, but start by looking for "heat shield". There are a ton of different types these days, and some are really expensive. But the basic stuff like in the photo works excellent for me.

 

[dllubin]

If you want a generic (less expensive) version, try ebay. Otherwise for a brand-name version try one of the big mail order parts houses like Summit or Jegs, etc. I don't recall the proper name, but start by looking for "heat shield". There are a ton of different types these days, and some are really expensive. But the basic stuff like in the photo works excellent for me.

Jeff:

I did a quick search of "heat shield" and like you said that stuff popped up. I have not looked too far but I did see a 12" x 12" sheet of Thermo-Tec for $13 on Amazon. I don't think cost will be much of an issue since the piece I need is so small. It was pretty interesting to see the large dollar signs for big pieces. Glad I'm not doing a firewall. I suppose that the best way to keep heat off the alternator and also the carbs would be to wrap the headers since that is where most of the heat is originating. I'll probably save that project until after I get the car put back together and running.

Thanks,

Don

 

[Dr.Jeff]

Don, I think "Thermo-Tech" is the stuff I have. I bought a small sheet at first, but over time kept finding more uses for it. So eventually I bought a much larger sheet.

I've given a lot of thought to heat management for automobiles. In the world of physics, there are basically 3 types of heat transfer; conduction, convection, and radiation. If you are interested in reading more, look at this:
http://www.physicsclassroom.com/class/thermalP/Lesson-1/Methods-of-Heat-Transfer

There are several products or techniques that I consider effective, and many that I don't:

Having parts professionally ceramic coated works pretty well, partly for heat containment (less heat escapes the hot part), and partly for excellent corrosion control (parts won't rust no matter what they are made of or how hot they get). This would be best for exhaust manifolds. But it is rather expensive to have done. There are additional types of "coatings" but they are pretty specialized and even more expensive.

The low dollar version is to wrap the part with "exhaust wrap" (ceramic fiberglass roll). This contains heat pretty well, but it also traps moisture / condensation. So corrosion becomes a big issue. This would work well on stainless steel components (won't corrode) or over ceramic coated parts (corrosion protected, plus double insulated). Good for stainless headers.

The opposite of "heat containment" is to reflect and / or insulate the heat away from a "cold" component. The Thermo-Tech mat we already discussed earlier works well for this. There are various other types of similar products; some work better than others and are usually priced accordingly. This method would be best for under intake manifolds or over sensitive parts (electronics, plastics, hoses, wires, etc). A good one for hoses, lines, wire harnesses, etc is a tube made of such materials that slips over them.

Another important aspect of heat management is to reduce the transfer of heat between hot and cold components with good air circulation. Continuous flow of cool air through the area carries the heat away. Some of the products mentioned above (heat reflection / insulation) require a layer of air between them and the part being protected, so look at the directions. If such a product is applied in direct contact it becomes very ineffective.

Ultimate protection would be to do all of these methods; contain the heat within hot components, insulate the heat away from 'cold' components, and further reduce the transfer of heat between those two with good air circulation.

Your heat shield is an example of reflective protection. Adding the insulation layer (as discussed) makes it much more effective at this. Put it onto the "hot" side of the shield. But you can carry the protection further by adding any of the additional means of heat management described here.

The X has a real problem with heat build-up in the engine bay. So consider other components that can also benefit from better heat management.

 

[dllubin]

I found a 12" x 12" piece of the Thermo-Tec stuff for under $10 and ordered it. I checked out a number of the header coatings, some of them costing more than I paid for the headers. I was more concerned about protection rather than thermal management so I ended up trying the Rustoleum 2000F paint. It is different than most spray paints in that it requires several heat treatment steps culminating at 600F. I sprayed it on and it looked like any other spray paint but after the heat treatment it looked more like the parts were powder coated. I will see how well it lasts. The paint I put on in the 80s seemed to hold up OK except down by the collector where I'm sure it was pelted by road debris as a matter of course (hangs low).

That heat transfer link looks like something I had in undergrad physics class years ago but nicely presented.

I never really had any heat issues with the car and probably would have not delved off on this tangent had I not ruined the alternator heat shield the other day. Some time after I get this thing back together, I'd like to put a heat shield under the carbs. I've got them insulated from the intake manifold with those phenolic looking spacers but there is a lot of heat radiated off the headers. The biggest problem is trying to adjust the carbs without burning your fingers off. As a result, I use gloves!

 

[Dr.Jeff]

Ya, as I mentioned heat coatings are expensive. Typically the high-temp paints do not hold up well but having baked it the way you did will help. There is a fairly new "ceramic coating" product that can be applied at home. It is like a very thin paint and applied the same way. But it does not require the processing to cure it like a normal ceramic coating (which is what makes this one a "home" application). I have some but haven't tried it yet. The material costs more than paint but much less than having the headers professionally coated. It is applied to bare metal so you would have to remove the paint you just did.

Perhaps the fresh, baked-on high-temp paint you did will be sufficient corrosion protection to add a header wrap over. This would give a huge reduction in heat transfer from the exhaust.

Although you say you never had any heat issues with the car, there is more to it than that. I'm not talking about it over-heating or running hot. I'm referring to engine efficiency. Thermal management plays a significant role in how the engine performs and its reliability.

Adding a shield between the exhaust manifold and the intake manifold/carbs will also be a big help. Engines really like cooler induction. And ones with this "counter flow" design, placing the intake directly above the exhaust, is particularly disadvantaged in this regard. Not only does the heat rise to the carbs and manifold, but to the air surrounding the filters as well. The same Thermo-Tech material will work great on a heat shield for this also. Same structure as the alternator shield, an aluminum plate formed to fit between the manifolds with the insulation material on the hot (exhaust) side.

 

[LarryC]

I fabbed up a heat shield between the exhaust and the AC compressor a while ago. My next step will be to put a layer of Thermo-Tec on the exhaust side to further reduce heat transmission. Header wrap on the exhaust pipes is also a good idea, which I intend to do at some point. I got the idea from the engine of a Fiat Multipla that came through Albuquerque during the Hemmings Great Race a couple of years ago. These guys were doing a transcontinnen

tal thing in the middle of the summer, so I figured they knew a thing or two. Here in the dry Southwest header wrap is not the problem that it can be in wetter climates, so I think I will give it a try. Already have it on a Bronco with exhaust pipes running near a gas tanks. Works wonders.

 

[dllubin]

Ya, as I mentioned heat coatings are expensive. Typically the high-temp paints do not hold up well but having baked it the way you did will help. There is a fairly new "ceramic coating" product that can be applied at home. It is like a very thin paint and applied the same way. But it does not require the processing to cure it like a normal ceramic coating (which is what makes this one a "home" application). I have some but haven't tried it yet. The material costs more than paint but much less than having the headers professionally coated. It is applied to bare metal so you would have to remove the paint you just did.

Perhaps the fresh, baked-on high-temp paint you did will be sufficient corrosion protection to add a header wrap over. This would give a huge reduction in heat transfer from the exhaust.

Although you say you never had any heat issues with the car, there is more to it than that. I'm not talking about it over-heating or running hot. I'm referring to engine efficiency. Thermal management plays a significant role in how the engine performs and its reliability.

Adding a shield between the exhaust manifold and the intake manifold/carbs will also be a big help. Engines really like cooler induction. And ones with this "counter flow" design, placing the intake directly above the exhaust, is particularly disadvantaged in this regard. Not only does the heat rise to the carbs and manifold, but to the air surrounding the filters as well. The same Thermo-Tech material will work great on a heat shield for this also. Same structure as the alternator shield, an aluminum plate formed to fit between the manifolds with the insulation material on the hot (exhaust) side.

Based on how the last paint job wore, I would say the header wrap would not be a problem with corrosion as long as I stay a bit above the collector. That was the only place I had a bit of rust after sitting a few inches off the ground for 22 years. Since I'm really more interested in insulating the upper part of the header, I think it should be fine - particularly if I start the car regularly to drive off the moisture.

Before I put the DCNFs on, I had a heat shield between the carb and exhaust. I also built a modified air cleaner with an intake fitted to accept a 4" hose that was routed to a custom 4" fitting attached to the driver's side air intake in order to provide cooler (denser) air. There was an improvement but much of it could have been due to removing the snorkel on the stock air cleaner which had an opening about the size of a quarter. I knew a guy who solved that problem by removing the stock air cleaner cover and replacing it with an aluminum pie tin with three holes drilled in it for the hold down bolts. That allowed air to enter around the entire periphery of the filter. It looked a little funky but it worked. My plan was to do a heat shield and air box with the DCNFs but shortly after I put them on, my daughter was born and priorities changed for a long, long time. I don't have much clearance between the intake manifold and the header but I might try some of that Thermo-Tec stuff on the bottom of the intake manifold and perhaps an aluminum plate as you suggest in between. Another approach would be a plate between the intake manifold and the phenolic spacers which could provide a much larger shielded area. I suppose I'd need one more gasket per carb to prevent leaks.

 

[LarryC]

I forgot to mention that another thing I did that is low-Therm-Tec, so to speak, was insert a sheet of the Thermo-Tec high-T fabric-backed high-temperature exhaust shield on top of the exhaust manifold just underneath the carb. The idea was to replace the factory metal exhaust shield in that area. It was a spur-of-the-moment-I-had-a-piece-laying-around thing. And it has been on there ever since. Works perfectly, conforms to the irregular contours, does a better job than the factory metal shield, and I notice delays the turn-on of the carb cooling fan by a good 5 to 10 minutes in the summer after shut down. It turns down near the alternator and keeps it from sucking in exhaust-heated air as well.

 

[dllubin]

I forgot to mention that another thing I did that is low-Therm-Tec, so to speak, was insert a sheet of the Thermo-Tec high-T fabric-backed high-temperature exhaust shield on top of the exhaust manifold just underneath the carb. The idea was to replace the factory metal exhaust shield in that area. It was a spur-of-the-moment-I-had-a-piece-laying-around thing. And it has been on there ever since. Works perfectly, conforms to the irregular contours, does a better job than the factory metal shield, and I notice delays the turn-on of the carb cooling fan by a good 5 to 10 minutes in the summer after shut down. It turns down near the alternator and keeps it from sucking in exhaust-heated air as well.

Larry:

That sounds like a good idea. Can you tell me which Thermo-Tec product you used and how it was fastened? Any photos?


Thanks,


Don

 

[LarryC]

Well it was what I had laying around, which was the clamp-on exhaust heat shield kit
https://www.summitracing.com/parts/the-11675
which had special grommets for the circle clamps. However, that kit is nice in that the edges are properly finished.
But if I were to source something specifically for that purpose I would get an equivalent sheet of their materials and cut it to fit. As to attachment, that is the thing: I didn't attach it at all! It just lays there quite happily, and now for several years.

 

[Dr.Jeff]

For the manifolds I also like a product that is made with two layers of sheet aluminum, with a "waffled" surface, and a insulation layer between them. This eliminates the need for a "air gap" that most heat shields require between it and the adjoining surfaces (something that's impossible to do in this case). I found a particularly nice one at the recent SEMA Show that I'll try when I make a shield for mine. The space between the intake and exhaust on the X is a challenge. This product can be cut, bent, shaped, formed, etc easily yet is rigid enough to retain the shape and position when mounted. Many OEM's use it in critical areas (the new Vette is one example). Comes in various size panels. I'll look for the reference to it (my desk is a mess lately). It's not cheap but its the best product I've found for this application.

 

[lookforjoe]

The stick on wrap / shield typically does not stay put over time. I have use DEI and another name brand that eludes me right now. It will stick to itself & never come apart, but if applied as a single sheet will typically peel over time, depending on the proximity to exhaust / heat. My solution for this is to rivet the heat film at even intervals with 'fender' washers to prevent it pulling off the rivet head. This has worked for me. I have to say that in most cases, mine has NOT been applied to a perfectly flat surface, and that fact may alter the long term adhesion.

 

[dllubin]

The old insulation was held on with bendable tabs from the factory. I suppose I could use those if the adhesive is not durable. Rivets could work too. The surface it goes on is perfectly flat. I've got it down to bare metal right now but plan to put a fresh coat of engine paint on it before installing the insulation. The 12" x 12" piece of Thermo-Tec showed up in the mail yesterday. It looks pretty generic to me - no packaging or any markings to indicate it was made by Thermo-Tec although that is what it was sold as.

I see you are from Rockland County. I used to date a girl from Nanuet many years ago.

 

[Dr.Jeff]

Sounds like a limerick: "I used to date a girl from Nanuet. She had a very nice..." I'll let you finish it.

The stick on wrap / shield typically does not stay put over time.

I have not had any issue with the self-stick product staying put, even after years of service. However I typically have not placed it directly next to an exhaust manifold, where the temps are much higher. And I have not placed it in a particularly harsh environment, like the under-carriage (i.e. on the bottom side of a floor pan, over the exhaust). I'm not suggesting those are the applications where Hussian had problems, just thinking it might have differing results depending on the circumstances.

None the less, I would not expect any adhesive product to work on a shield placed directly between the intake and exhaust manifolds on the X. That is way too hot and pretty much in direct contact. That's why I suggested the other product with multi layers and insulation between them (I still don't remember the name of it).

With all this in mind, here's another suggestion for your alternator shield application. Maybe try cutting the material about 2" larger than the metal shield on all sides, wrap that extra amount over to the other side of the metal, then put the rivets/washers through both layers of the material and the metal in between (hope that makes sense).

Regarding those "tabs" on your shield. I see they are not at the edges of the shield, but well into it. I think I'd flatten them and make the insulation go all way across the entire shield, for added heat protection.

 

[lookforjoe]

Before laminating & riveting the underside edges. Did the same for an alternator shield that comes off the right side palte, just don't have a pic. I do feel like it makes a difference.

Used it for much the same thing in my old Volvo - between the header & the compressor output (not visible)

Jeff, if you didn't use it in a harsh environment (temp wise) then, what's the point

 

[lookforjoe]

I see you are from Rockland County. I used to date a girl from Nanuet many years ago.

I moved to Nyack/ Valley Cottage area in 1980 from England. Been here ever since, except for a short trial run in Pasadena (1982). Nanuet is just a few miles away.

 

[dllubin]

Sounds like a limerick: "I used to date a girl from Nanuet. She had a very nice..." I'll let you finish it.


I have not had any issue with the self-stick product staying put, even after years of service. However I typically have not placed it directly next to an exhaust manifold, where the temps are much higher. And I have not placed it in a particularly harsh environment, like the under-carriage (i.e. on the bottom side of a floor pan, over the exhaust). I'm not suggesting those are the applications where Hussian had problems, just thinking it might have differing results depending on the circumstances.

None the less, I would not expect any adhesive product to work on a shield placed directly between the intake and exhaust manifolds on the X. That is way too hot and pretty much in direct contact. That's why I suggested the other product with multi layers and insulation between them (I still don't remember the name of it).

With all this in mind, here's another suggestion for your alternator shield application. Maybe try cutting the material about 2" larger than the metal shield on all sides, wrap that extra amount over to the other side of the metal, then put the rivets/washers through both layers of the material and the metal in between (hope that makes sense).

Regarding those "tabs" on your shield. I see they are not at the edges of the shield, but well into it. I think I'd flatten them and make the insulation go all way across the entire shield, for added heat protection.

Yes, they have already been flattened. It was a whole lot easier to clean the part up after I flattened them with a hammer and anvil.