Dynamat Extreme works incredibly well for noise damping. Note that you don't need to cover everything, you just need ~1/3 coverage per panel.

I don't have any real experience with modern heat insulation but the Dynamat would go under whatever you choose.

 

I know Dynamat is a highly revered and effective product but I have pause to reconsider it. The downside of it I see is A) It is next to permanent .. B) It can be construed by future buyers as a cover-up to rusty floor pans.. I much prefer the type of deadening from the factory that Classic Alfa sells. I don't see the point of deadening the sound in an open car more than what was provided by the factory. I do know they are prone to floor heat from the exhaust as they have heat shields in those areas. Again the fibrous material used by the factory is more effective and reversible and renewable.. I question the tar based Dynamat on a hot floor panel. Just my 2 cents for things to consider.

 

I can tell you without a doubt that Dynamat works better than the OEM fibrous stuff. Though in terms of construction they're not as different as you think: the factory stuff uses bitumen (tar, basically) as the sticky stuff instead of the butyl rubber of the Dynamat. Butyl is denser and more effective, though.

As to open-top cars, it made a huge difference on the Giulia Spider in terms of the car feeling solid. The stock doors on that thing felt like they were made out of old aluminum cans when you banged on them or shut them. I stuck a maybe 18"x12" piece of Dynamat to the outer skin and it was night and day. I put it on the floors, firewall, and under the dash too and it made the car just feel more solid overall.

Haven't had any issues with floor or firewall heat, though in those applications you might want to seal the edges with the tape they sell.

 

Thanks for the info! Did you install anything on top of the Dynamat to help with heat insulation?

Best regards,

 

I'm more focused on floors. I think the doors on a Giulia Spider of the 60's had a cursory spray on patch of deadening inside the doors similar to the chassis undercoating that cut down on the "tin can" effect. Anyway, it's always good to share thoughts. Also, the Giulia Spider of the 60's is a completely different animal to a '73 Spider when it comes to heat on the floor.

 

amazon.com
LINGDA 21.53 SqFT 10mm Heat Shield Thermal Sound Insulation Proofing Deadener Mat Car Noise Control Acoustic Dampening Moistureproof Waterproof (40"X80")

 

I'm going with the existing Kilmat already on the footwells and floors under the seats (installed by my body guy), remove the old original crappy Jute insulation that is still wrapped around the shift tower (not sure why he didn't remove/replace it), add Kilmat over the center tunnel, between the seats (nothing is there at the moment) then use Jute thermal insulation from secondskinaudio.com under the new rubber floor mats, around shift tower, over the center tunnel and possibly under the seats if it fits with the new rear floor/tunnel rubber mat. The insulation is 3/8" thick, so it should be good to replace the original crap that's wrapped around the shift tunnel and will feel good under the floor mats. Just not sure if it will work under the seats/rear floors. I'll find out. That's the current plan of attack to reduce vibration noise and heat in the cab.

 

A second look at the Jute insulation around the shift tower indicates it's still in pretty good shape, and I'm thinking it would be wasted effort to replace it. But extending it over the center tunnel with this Jute product seems like a good idea, with Kilmat (same as Dynamat) added under that. My only concern is fitment of the rear floor/tunnel mat with an additional 3/8"+ 80mil Kilmat thickness in place. And I'm also second-guessing myself on putting the Jute insulation under the seats below the rear floor/tunnel mat, as it could potentially retain moisture down there. I still want the Jute under the new rubber floor mats below my feet for comfort and noise/heat resistance. I think it would make sense to glue the Jute to the bottom of the mats themselves, rather than to the floor.... thoughts?

 

My '84 has the cat right under the driver's seat, and when I bought the car huge amounts of heat poured into the cabin from the boot opening around the e-brake handle. In the hot So Cal summer sun I was roasting.

I temporarily used a zip-tie to seal the boot tight to the handle and substantially reduced the heat. As I've returned the car to original, the new e-brake boot doesn't admit heat and no need for the zip-tie. . . . .

David OD

 

One thing to check on before putting dynamat (et al) on your floor is the clearance between the seats and the carpet/rubber matting . If the dynamat is too thick you can have interference problems with the carpet/ mats when you try to slide your seats forward.

I've used the approach of putting a heat shield on the muffler itself with good results.

I used this
Muffler Armor.

However their prices have gotten... high... and if I were doing it now I might use a generic substitute.

I put it on top of the muffler using metal 'zip ties' and left the bottom side open to the air.

 

Thanks, great point. My body guy already put Kilmat under the floors, and that may explain why the seats do seem to be difficult to slide to and fro. So adding anything else under there sounds like a bad idea. I'll try and confirm.