I am ready to install the underdash insulation on my 68 Cutlass. There was none there when I removed the dash, so I am unsure how it attaches. Are there any mechanical fasteners, or is there an adhesive used? Also, does the tar side get unwrapped from the clear plastic? Which side (jute or tar) gets placed against the dash. This is for the upper dash area, same as this kit... https://www.yearone.com/Product/1964...***-442/lp6271

Thanks.

 

I believe the sticky side is up and the firewall insulation goes on by push plugs. also do not forget to make slits if aftermarket for accesories also.

 

Thanks. I can see where the push plugs go on the lower rubber insulation but I don't see any places for them on the upper part. Could you give me an example of where I might look for them to attach?

 

I believe the push plugs are for the firewall pad only. IIRC, the under dash pad is glued on.

 

Is the tar back meant to be heated and stuck, or would 3m super 77 be used?

 

That's not tar on the part (click and enlarge the pic)...it's likely a plastic layer. On the originals, the insulation side got glued up against the underside of the dash and the plastic side faced down (what you'd see if you stuck your head under the dash and looked up at it).

Factory appears to have used some sort of spray adhesive to stick this on so another spray adhesive should work....BUT...spray BOTH surfaces with the adhesive (read the back of the can).

To ease installation you can just put glue along one edge (maybe the edge closest to the firewall) of the dash metal and the insulation material....wait for it to tack up and sort of "hang" the piece in there. Then you can work your way forward in increments..spray a strip of both surfaces, wait for it to tack up, stick it together, etc. This way you aren't trying to spray the WHOLE THING at once and try to handle the thing.

 

Does this insulation do anything? Noise suppression or hold cabin heat better?

I had considerable dash diving missions fixing sparky things under there. 1967 insulation had tuned to brittle fluff so I scooped, plucked, vacuumed and air-gunned it out-a-there. Never considered putting that evil stuff back in!

 

you are completely RIGHT on that original stuff....WHAT A MESS!! Think about it everytime you hit a good bump with that old stuff in there...here comes some more mystery dust/particles.

Probably a noise barrier of sorts.

 

Whatever was originally there from the factory had disentegrated by the time I got the car. The new stuff I installed (thanks for the tips from everybody) seems robust enough to last at least 30-40 more years.