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MG MGA - Sound Deadening and Thermal Insulation

This is a spin off from the thread on Under Dash Cover. There is a BIG difference between thermal insulation and accustical damping.

sound deadening materials are usually high density (heavy) and fairly thin, being glued directly to a body panel. Much of the effect comes from damping vibration by increasing mass of the panel, thereby lowering the natural resonance vibration frequency. This material will usually have low thermal resistance.

Some additional sound deadening effect can be gained using a composite material with a low density absorbent underliner and a high density facing material. This traps accustical energy within the softer material between the panel and the face layer. This material may have slightly better thermal resistance by virtue of the low density underlayer (mostly air space), but it will still be a fairly poor thermal insulator if it is thin.

Better thermal insulation is gained using a low density material (high air content) with more thickness. Heat transmission is inversely proportional to the thickness, with a point of diminishing returns. A layer about 3/8 inch thick under the carpet can do wonders for stopping heat flow to keep you cool in the summer and warmer in the winter. Given the thickness and the rigid face layer it is a fairly good sound barrier. This stuff can also be quite light weight and downright cheap.

I bought a 4 ft x 6 ft roll of the cheap stuff from J.C.Whitney several years ago for $19.95. The facing is a double layer of aluminum foil with a very thin 1/4 inch mesh thread for reinforcement. Underneath is a 3/8 inch layer of "natural fiber" which appears to be shreaded urethane foam (similar to felt) with minimal random thread inclusion to hold it together. The full roll was about 5-1/2 pounds. I used only 1-1/2 ft off the 4 ft wide roll, placing it under the seats. The last carpet kit I bought from Moss Motors included felt underlayment for the tunnel and front footwells.

If you can do this before the wiring harness is installed it would be easy to insulate the underside of the heater shelf and back of the upper bulkhead, which is a single layer of sheet metal prone to transmit heat and noise from the engine bay. You can also glue this stuff underneath the battery cover, which is a significant source of noise transmission from the exhaust.

Just putting felt under the tunnel carpet makes it go from burning your leg to just warm in hot summer driving, and keeps you significantly warmer in cold weather. I may have more to offer on this subject if this thread takes off like I expect it will.
Barney Gaylord

The big Healeys appear to have an even bigger driver compartment heat problem than the MGA's. Several Healey owners have used this koolmat mentioned in the origional thread and they rave about how good it insulates. I am doing a Healey now and I am debating on using this product. I will wait to see what comes from this thread. Have a good day!

John Progess

Hi John. I used to own a big Healey years ago, and can attest to the severe passenger compartment heat problem they had. The twin exhaust pipes ran beneath the driver's side (metal) floorboard, and despite asbesdos shielding, the heat from the exhaust, and the engine was in a word, unbearable. After a long drive one summer, I found that the crepe soles on my shoes had melted and were stuck to the floor mat, due to the cockpit heat! MGA's also have a cockpit heat problem, but not anything near as bad as the Big Healeys! Since I am currently in the process of re restoring my MGA, I plan on doing something about the somewhat uncomfortable cockpit heat, and have already been investigating appropriate heat shield materials. If you go on ebay, and do a search for auto insulation, you will find several listings for various types of insulation. Most of these seem to be fiberglass/foil or rubber/foil compositions. These products are advertised as being good for about 1200 degrees F. I obtained samples of some of these products for testing and frankly, I am not terribly impressed. I then did an Internet search for industrial grade insulation, and have found a ceramic fiber insulation that is supposed to be good for about 2600 degrees F, and am trying to obtain a sample of this materialfor testing. If anyone is interested, I will let them know how the ceramic fiber insulation tests turn out, if and when I get samples. Cheers, Glenn

The temp ratings for insulation are for the MAX temp it will survive under. The coefficient of heat transfer has nothing to do with maximum ratings. If the maximum temp involved is say 500F, then insulation rated for more is not necessary. In fact, most high temp rated stuff is not very good at actually insulating efficiently against heat transfer, it's just the only thing that will survive at high temps and still do some insulating. Insulations rated at lower temps will be much more effective and far cheaper.
FR Millmore

Glen, I am looking foward to the results of your research. I to remember the days of a hot cockpit from the days of my youth in my spitfire! My MGA (Frame off) is almost ready for paint. I would like to insulate the underside of the shelf before I place it on the frame.
Barney, thanks for your insight! I am looking into what JCW offers today......
Bill Robinson

You might try Sleepy Hollow Supply, ltd at Check out their CERA-FOIL product. I installed it in my MGA fifteen years ago and then in my TD three years ago. Does the job. Marvin
Marvin Stuart

Hi FRM. Clearly, MGA cockpit temperatures should never reach anything close to 1200 degrees F! I do realize that the advertized temperature is the maximum heat the material will tolerate. I was just thinking that perhaps the more expensive and exotic 2600 degree rated ceramic fiber stuff might have better insulative qualities than the less expensive fiberglass and rubber based insulations I have tested so far. As you have pointed out though, that will not necessarily be true. Your comment about high temperature survivability, vs a less efficient heat barrier is well taken. As always, your comments, insight, and expertise are most welcome. Cheers, Glenn

There was a fellow on one of the forums making up Koolmat kits for MGAs and Magnettes.
I don't recall who it was but I will see if I still have him on file.

Rich McKIe

Found the info.
Mike Hickman was doing the pre-cut kits.
They have been getting good reviews.
his e-mail is sandyandmike

Rich McKIe


Congratulations on starting the longest ever thread title!

I recently bought the same stuff that you did from JC Whitney in the hope that it will reduce a little of the cockpit heating. While it would be preferable to apply the material before putting the wiring harness and all of the behind the dash connections, it isn't absolutely necessary. I have applied it after having passed all the wiring through, not as a single sheet, but by cutting, glueing and fitting individual bits in place. The effect should be the same, it was a little more work, but no worse than any other under the dash job. But, until the car is back on the road, I won't know if it has been worth the trouble. I'll let you all know when that day comes.

Dan Barton

Has anyone heard of lizardskin ( It is a ceramic insulation that paints onto the panels and is said to deal with both heat and sound issues. It is sandable and paintable and goes on to credit card thickness for ideal effectiveness. It cost about $180 for a cars worth and could be sprayed onto the inside of the entire car (including the roof of the coupes). Yes, expensive, but could help eliminate building up surfaces with bulky mat material. I have not seen this product in person but am intigued. Does anyone have any further knowledge about it?

Randy Myers
'59 roadster, coupe

As I stated in the other thread, I have installed a product called BQuiet. Thru Barneys definition, I am now more likely to call it sound deadener than insulation. It does seem to reduce some of the heat inside my Coupe. So ,I will leave it there are proceed to ADDING the insulation products directly on top of it. Will it be sufficient to just add regular carpet (chewed rag) underpadding as a heat insulator or should I go for something more high tech. Remember this means I will have a layer of BQuiet....carpet under padding and then the carpets. Heck, if I put any more stuff I won't be able to get in the car. Gordon
Gordon Harrison

I am thinking of puting aluminium sheet somewhere half way between muffler and floor boards to reduce heat transfer. Anybody to comment?

Moss offers one. I would think you would want some space between the floorboard and the shield. Not sure if Barney has addressed this.


On my '56 roadster I installed, some years ago, one sheet of thin steel beneath the drivers seat and up the front of the driver's foot board between the exhaust and the wood floor. I mounted it on the exposed ends of the floorboard screws, using suitable nuts.(The existing captive nuts acted as spacers)
The result is an air gap of about 3/8 - 1/2 inch between the steel and the wooden floor, and it seems to work well. I was always told that the best heat insulator is air (that's why they use it in double glazing, and because you can see through it!).
I will do the same on my 58 Coupe, but it will be easier as I will fit it before the body goes onto the chassis and before the engine is installed.
I will also put something under the heater shelf and on the inside of the vertical panel under the dash, as suggested by Barney, before installing the wiring etc.
Mike Ash put some expensive material on the underside of his Coupe's roof to keep it cool - I'm going to paint my roof white which will reflect the sun.
Seeya all at GT32.
P. Tilbury

A couple of other products that the Healey guy's are using are Dynamat which is a aluminum backed butyl rubber product and is adhesive backed. For the transmission tunnel an aluminized heat barrier product again adhesive backed is available from pegasus auto racing ( For a insulating underlayment check out The Healey owners have really done alot of reasearch into solving the heat problem in the cockpit. Have a good day!

John Progess

Barney I am trying to find what I lined my coupe with. It was made for MBenz hear in South Carolina I had a few peaces left over but unable to find have a look this is the under side of my coupe you will see what I used (1/8 fiberglass with 22g aluminum with self sticking peal off). I installed on the out side of the floors and then installed the floor boards, I used it on the inside of the lid and installed on the outside of the toe boards also I used the liner from Moss. Just to give you an idea of how great it works it was 55d (F) I had to turn on the heat to warm up my toes. I do not even feel the heat from the exhaust pipe under the seat.
Thanks for all the great help, if not for your web-site I would have been up the creek
I hope your frend: CLiff(SC)

Regarding Lizard Skin, I have purchased and applied it to my 58 coupe. However, I haven't driven the car since it was applied. However, putting a heat gun on one side and my hand on the other indicates it should help a lot. Also, rapping on the roof indicates its dampens noise pretty effectively. I put it on the underside of the tranny tunnel, battery cover, underside of the roof. I applied it with a foam brush. Keeping the foam brush wet help a lot. If you want to spay it, you must rent or buy (even more $$) a special spray gun if you want to spray it.

G T Foster

Oh, did I mention that, if you want to spray it, you must rent a special spray gun, if you want to spray it. But, only if you are spraying it...........:)

G T Foster

Does anybody no if the "Under Dash Pad" by Moss 9241-980 is foiled backed? or what the thickness is?
Bill Robinson

I have one in hand. Moss number 241-980. 1/8 inch thick light brown felt plus a 1/32" thick tough textured black vinyl skin facing. No foil.
Barney Gaylord

Note that plywood with carpet is a pretty good sound deadener, so it probably wouldn't do much good adding sound deadening material to the MGA floors. For that you should think more in terms of thermal insulation quality.

Sound deadening does the most good on single layer sheet metal panels, like the heater shelf, upper bulkhead, tunnel, battery cover, inside the door skins, in the Coupe roof, and inside the bonnet. It also adds weight and doesn't make the car go any faster. So I tend to think more about thermal insulation for temperature control.

Martin, -- The original under floor heat shield (as supplied by Moss) is a sheet metal pan covering a thin layer of insulation, screwed directly to the floor underside. It covers only a small area below the seat. The intended function is to prevent fire in the plywood and carpet (and seat) if (when) the pipe makes contact here after the rear muffler hanger breaks. Keep an eye on those pipe hangers, guys.

I have been looking at the Autmotive Insulation web page here:
This looks like very good thermal insulation in a thin package. The material is 3/16-inch thick "closed cell microcellular polyethylene", does not hold moisture, and is supposed to be thermally as good as two inches of fiberglass. This could do well all around the cockpit as heat insulation. It also has bright aluiminum skin on both sides for 97% radiation rejection, so it should be good above the exhaust pipe if you put it on the bottom side of the floor, and should keep the bonnet (engine cover) cool if you want to line the underside. It also claims to be a sound deadener, but no quantitative numbers there, so that effect is ill defined (and maybe not so amazing). The best feature may be that it's relatively cheap at $0.69/sq.ft. I have a sample coming and may comment more on it later.
Barney Gaylord

Would you suggest using Lobucrod insulation in place of the regular carpet underpadding or as an extra protection conmined with the underpadding? Gordon
Gordon Harrison

I don't have any recommendation on this product yet. I'm waiting for the sample. It will be fairly good thermal insulation in a thinner form, but not so good padding to cushion your feet. Being thin it would be good insulation inside of the doors and in the Coupe roof. Being reflective it could be good under the bonnet. Not sure about the temperature tolerance yet. It is rated up to 450dF, so it may NOT be good in close proximity to the exhaust pipe.
Barney Gaylord

Using sound insulation on an MGA Roadster is probably a complete waste of time (though it might be useful on the coupe. I also drive a Boxster and can assure you all that, once you put the top down, the decibels go up enormously. Heat insulation must be the way to go and, if it deadens the sound a tad, so be it. I wonder how many of us bought our "A"s for their quietness?
Dan Barton

Hi All
Have just read this thread.
I finished a body off restoration of my A 1 month ago and followed some of Barney's recommendations plus my own. Still HOT in the cockpit! For the record, I used (illegal) asbestos on the front panel and both panels under the left floor; zinc plated the underneath of the tunnel and then covered it with a cloth insullation; underlay beneath the carpets and insullation on the inner fire wall and beneath the scuttle. Can't remember the brands of insulation used but were the most expensive, hence hopefully the best availible. Obviously not so..... Still love my A.
Dave Godwin
David Godwin

Hi guys, i know a company that you might be interested in

They specialise in Koolmat insulation products and have MGA kits avaliable. There's an interesting article from a guy that used one of the pre-cut insulation kits on his MGA

I hope this is useful to you.

Matt Unger
Matt Unger

In the UK, I'm about to fit something called Tri-Iso Super 10 under the carpets - it's a high-spec roof insulation material with several sandwich layers of foil, foam etc. - very thin and very high thermal insulation properties.

I will report back on performance - has anyone else tried this stuff?

Richard Ross

After I restored my 1600 coupe I was very disappointed with the amount of mechanical noise in the interior (commented upon in the original road tests). I consulted a friend who is a distinguished retired acoustical/sound engineer. On his advice I put a lead light in the engine compartment one dark night and "zapped" all of the "stars" in the firewall (ie loose fitting grommets, "spare" holes, etc which he said would let much more sound through than any insulation would combat) with silicone, then obtained some insulation material consisting of two layers of thin plastic foam with a sandwich of lead film between them (the factory put plain foam on the firewall-fairly useless as a sound barrier). I think that I also put jute-felt under the carpets but I don't think that did much. The nett result is amazing, our coupe has been absolutely transformed!
Barry Bahnisch

I posted this earlier, but it's gone missing, so:
I sent Barney my dissertation on all this, and he has graciously put it up at :
for all to peruse. It covers most of the stuff raised and more besides.
FR Millmore

With all the talk about heat shields etc has anyone tried "Exhaust Wrap" around the exhaust pipe itself ?
I've thought about trying it but never got round to it.
I also found that the horizontal chassis "goal-post crossbar" on which the pedals are hung gets very hot (particularly in the passenger footwell on my RHD roadster)and I have insulated it using commercially available car carpet underfelt ,cut to shape and then bolted on using the various spare threaded holes in the "crossbar".



Check the archives for both A and B. Topic has come up a number of times. IF I remember corectly the wraps tend to trap moisture and accelerate corrosion. A coating such as Jet Hot seems to get good reviews for keeping engine compartment temperatures down.


58 A
Larry Hallanger

This thread was discussed between 04/03/2007 and 27/03/2007

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