Sound insulation -



I seen the 1st U-tube Vid Grumpy recent prior Grumpy.
Its a nice lesson in Internal Combustion Physics at work for you.

Tonight I will post a few old HO RACING ARTICLES.

Need to eximane close as a group.
Pontiac 421& 428 &455 hard to find today.

A Corvette shoud stay Chevrolet powered too.


solid fixture here in the forum
KEEP IN MIND YOU MAY NOT ALWAYS WANT TO REDUCE THE SOUND, IN FACT ONE FACTOR THAT MAKES THE USE OF A DUAL QUAD SETUP ON A BIG BLOCK, is that three stage sound as the various stages of the throttle blades on the carbs open .


and there are cold air duct hoods that make routing cold air to the engine efficient





Bringing the thread alive Grumpy.
Good info in the 2nd Link.
WOT Action for Max Power.
The link still works.
Trapped in the old website yet.


Well-Known Member
I ALMOST completed installing Butyl sound-deadening panels in my 79 last weekend. (I still have the rear section and behind the driver's seat area to complete.

I did want to comment on the difference between some of these very similar products and the products melting from above and current pricing of the different products in the sound-deadening category.

SOME of the Butyl-Rubber sound-deadening products are a blend of Butyl-Rubber and Asphalt. These tend to have worse sound deadening / absorption properties vs. pure butyl-rubber AND their performance at sound deadening declines as temperatures increase- they also have lower melting points.

The thicker the material, the more effective they are.
For the comparison below I attempted to select versions of each brand that were 80mil (2mm) thick when available.

1. Dynamat: Comes in the super thin "Superlite" which is .045" thick / 1.143mm and "Xtreme" which is .067" thick / 1.7018mm; 36 sq ft costs $200
2. FatMat: 70ml thick version comes in a 25 sq ft pack for $80
3. Hushmat "Superbulk kit"- only 1.5ml thick, 36 sq ft $170
4. Noico: This WAS the Amazon recommended brand until a few months ago and contains a lot of asphalt so it melts at high heat AND smells like rubber/ tar. It WAS 80mil thick and cost only $68 BUT it's manufactured in Russia so you won't find it on Amazon any more anyway. Good riddance to it's stinky asphalt smell!
5. Kilmat: 80 mil, 36 sq ft now costs $69 today; Silverfoil (I paid $58 in Feb 2020)
6. Siless 80 mil, 36 sq ft ; $69 -black foil no lettering

The Kilmat and Siless are by far the best deal out there right now. The Kilmat doesn't have the asphalt smell of the Noico. I can't speak for the Siless as I haven't used it yet.
[Edit] I've now used the Siless and can confirm that there is no asphalt smell from the Siless products either.
Kilmat Sound Deadening Installed-mostly.jpg

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Well-Known Member
Another sound and heat insulation option that I DIDN'T see covered on here is special carpeting set options from ACC.

ACC offers both a "mass backing" option that adds a 45 mil thick Ethylene Vinyl Acetate backing to the carpeting, but it only gets applied to molded pieces and not die cut pieces like flat cargo and side panels.

They also offer a carpet set pile upgrade that they call "Essex Plush", it includes 40% denser carpeting pile and is 3/8" thick instead of 1/4" thick so again provides additional sound deadening and heat reduction vs. standard carpeting pile.

For my 79 C3 I'm going with 3 layers of interior sound and heat reduction:
1. The 80 mil Kilmat sound deadener
2. A 3/16" thick, aluminum backed closed cell foam (From "VetteNuts" who sells pre-cut kits for most Corvette generations)
3. The ACC Carpet set with the mass backing and "Essex Plush" pile. -I shopped every major Corvette supplier's best Christmas sales and special coupon codes in Dec 2020 and the regular everyday price at RockAuto beat every single one of them, for what that's worth.

On the exterior of the car I'm going with WisAuto Aluminized stick-on Heat Shield sheets on the firewall, AC evaporator box, under the foot wells and part of the trans tunnel. -I know some folks go with the Lizard Skin ceramic paint in those area, which seems like a really good option.

The AC Evaporator boxes tend to get forgotten but some C3 folks will go to exorbitant lengths to get cold AC and the passenger exhaust manifolds/ headers are sitting right next to the AC evaporator box, so it seems like the perfect place for a heat shield that reflects back that radiant heat.

I also have a transmission tunnel foam collar that blocks engine bay heat from migrating into the top of the trans tunnel.

Image showing the thickness difference between standard ACC Carpet pile and the Essex plush:

In my life I moved from the quiet of Indiana cornfields, to the quiet of a small town in Ireland (although we had fog horns and a commuter train), to the constant barrage of noise that is living in a Seattle suburb so for the past 3 years I've been adding lots of noise reduction to my life wherever I can. Quiet appliances and noise reduction products (I even applied noico panels to the inside of my washer and dryers panels; I put my garage air compressor into a garage cabinet and covered it's walls with sound deadener products, mass vinyl sheets in the attic over the insulation, etc..). I love the sound of my Vette but I want to cancel out the annoying sounds and get rid of the footwell inferno. I'm hoping my efforts pay off.

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Well-Known Member
I ran out of Kilmat and needed more to finish the rear cargo area and over the rear wheel wells. The Kilmat was delayed for a few weeks getting to me so I cancelled the order and ordered the 120mil version of Siless, which I think is the thickest Butyl mat product sold. $69 for 30 sq ft.

I got it all installed. Then installed my aluminum backed closed cell foam "VetteNuts" kit and the ACC carpeting kit everywhere but the big piece in the rear (I still need to get that one done). -I'll post pictures later today after my big meeting coming up in 15 min...

I used the SEM black dye on the seats and seat cushions too. SHOCKED at how amazingly new they look now.

My 5 point seatbelt harness bar "Shark Bar Series 2" also showed up this week so I'll get to mock it up for installation and figure out where to cut the carpeting for it.

Interior is getting SOO close to done!



Well-Known Member
Siless120 mil on the wheel wells and in the cargo areas.
Rear Siless 1.jpgRear Siless 2.jpg

Apparently I forgot to take a still photo of most of the closed cell foam so all I have is my too long-winded video:

Last picture is mostly a celebration that the front ACC Essex Plush mass-backed carpeting is in. Perfect fit in the passenger. Just a bit of trimming to clear the gas pedal in the front mostly.
Carpeting Front- complete.jpg
Plan is to burn-in the holes for the seat bracket bolts and the seat belt fasteners using a 10mm socket heated until it's glowing red hot. (First poke a nail through the center of each hole and then just center the hot 10mm socket over the nail head. Supposed to make very clean and fray-resistant holes without the need for the cheesy looking flaps.

My new speakers won't fit behind the original grills so I'm installing boxes that sit on the rear wheel wells that still allow storage of the T-tops and don't block any light or the cargo area lid.


Staff member
Looks like an expert job !

Did you have a template to cut out the insulation or did you trim it after you placed it ?


Active Member
I used the German version of Dynamat called Alubutyl (pretty much the same, but for a fraction of cost).
And between the Alubutyl and the carpet, those heavy anti rattle mattes (I think they are pressed out of rubber waste) that you put under your washing machine. Works quite well so far - I don't have a comparsion to "professional" car sound deadening materials though, but it's good enough for me.



Well-Known Member
Looks like an expert job !

Did you have a template to cut out the insulation or did you trim it after you placed it ?
It's not an expert job, but it's done at incredibly slow turtle speed so it can simulate an expert job in terms of quality. ;-)

The closed cell foam insulation set that I bought ($99 2 Christmas's past on a big sale) came already cut for a C3, so I was able to use those pieces as the templates for the butyl mat sheets for all the intensely curved pieces (those rear wheel wells in a C3 would be an install NIGHTMARE otherwise).

I basically just held the pre-cut insulation pieces up where they went and noticed if I wanted any areas slightly bigger then used them as a template on the butyl sheets and modified, accordingly.

For the places where I didn't have the insulation to use as a template (storage boxes), I just used the peeled off butyl sheet backings to make a template -lay them over where I want them to go and then trace the outline with a black magic marker and then cut them out and use that as the template for the butyl sheets.

AdamTracing Butyl Curved Shapes from VetteNuts Kit.jpg