I'm starting on the empty shell of my '70 W-31. I would like to apply a sound/heat proofing material to the floor pan and firewall. I'm questioning the thickness and which Dynamat product to use. I'm thinking of 1/8" Dynamat on the firewall and pan with an additional layer of 1/4" Dynaliner on the firewall. Yet I don't want it too thick that it may interfere with carpet and trim. Any thoughts or experience would be appreciated.

 

I think you have the right idea using a butyl for acoustic and an insulator to keep heat out (or in if its winter).

FWIW, Dynamat and other equally good products with Butyl-like stuff on one side and foil on the other are sound attenuators. Period. The tar-like underside is going to absorb heat not reflect it back. So they are poor at insulating. They don't eliminate sound but keep it from reverberating. Car rattles turn into that solid sounding 'thunk' instead of a tinny rattle.

Dynamat is most useful in conjunction with high end audio systems but much more expensive than a similar Butyl and foil product made by Noico which does the same thing at a lower price.

If you want to both reduce sound level and insulate (who doesn't) then you need a second product which will at least insulate and provide some sound reduction. I like Noico Liner (Manufacture part number: NOICOSPL04) Its only 1/6th inch thick and fairly light weight so will not add much to bulk or weight. It doesn't absorb moisture. Note, this is not the butyl mat but a different product. Dynaliner which you mention is probably a similar product but likely more expensive like the Butyl product made by the same company.

I used Dynamat Butyl on a 1936 Street Rod and Noico Butyl on my 47 Olds and cannot tell the difference except Noico is about half the price of Dynamat.

I didn't use an insulator on the 36 but intend to on the 47 even though its a convertible. Lots of heat from the 461 on firewall and floorboards. I'd like to keep as much as possible outside.

That's my limited experience related to your question. There is quite a lot of information on the Internet as well. Others may have a different recommendation.
Jerry

 

After trying to remove that stuff for a floor mod on a current project, and seeing first hand some of the inexpensive brands ooze out of door openings on a hot Texas summer day, I will never install any of it on any of my vehicles.

 

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I agree. Don't use the inexpensive stuff that runs about $20 a roll.

Beware, the inexpensive stuff is mostly meant for mobile home/housing use and is NOT meant for cars. I wouldn't install it on any of my cars either.

The good sound attenuating products are Butyl covered with foil.

The cheap products are ASPHALT products not BUTYL. They are meant as roofing material. There is bad information out there on the Internet saying you can use this on cars and its only 1/4th the cost of the Butyl product which is meant for car use.

Asphalt will run in extreme heat and it smells when hot. Typically these are cheap, narrow rolls that can be purchased at the big box stores like Home Depot and Lowes. That stuff is inferior for car use and will "ooze" in very hot temperatures as has been reported on Internet reviews of various heat and sound treatment products. You get what you pay for.
Jerry

 

I will be using lizard skin on the current which is sprayed on and seems to be a better choice. They have both sound control and heat shield.

 

you can make lizard skin..cheap..theres nothing in it but latex paint and glass spheres do a google on home made lizard skin..the guys on the the garage journal have it all layed out..where to buy materials etc..and they have engineers that are members that have broken the formula and tell exactly what it is..id bet theres a lot on the HAMB too...