Engine bay sound insulation?

[EsbenDenmark]

Finally done fixing up the truck and esp6the engine bay. Unfortunately the old firewall dampener is dead and in the trash. I have not been able to find a new or used.
So what can I use instead? I was considering a Dynamat Hodliner but are a bit worried it will soak up spray water and always be wet.
Don't want the rust to come back!
I have already put quite a bit of sound insulation inside the cab but want to get that extra layer on the firewall.

Any ideas how to make a good sound insulation on the firewall.

 

[RhinoRig]

I used the dynamat hood liner and it definitely works. Not sure about moisture being held and not sure how it would get there. It’s outer skin is a foil-like material that’s pretty tough and waterproof. I used regular dynamat inside the cab on the firewall.

 

[EsbenDenmark]

I used the dynamat hood liner and it definitely works. Not sure about moisture being held and not sure how it would get there. It’s outer skin is a foil-like material that’s pretty tough and waterproof. I used regular dynamat inside the cab on the firewall.

Good to hear that I am not the only one with that idea.
How did it turn out? Did it help with engine noise? Any chance you post/send a picture or two of the result?

I was not too worried about the outer skin but mostly the lower edge..(that's where the old so called dampener thing was rotten) but I guess I could seal that with some aluminium tape.

 

[Tigris]

Back when I had an FZJ80, I recall using a sprayable product on the entire floor pan and the firewall (engine side) because I too wasn't keen on the idea of using material that could hold water/dirt etc.

I don't remember the name of the product but it wasn't cheap, came in a 1 gallon can, and had a picture of a knight on it. I used a bedliner gun to shoot it in. The stuff was thick like a bedliner, it went in blue but cured flat gray (same color as primer).
Along with bethyl sound barrier, high mass carpet and carpet backing, and even 1/8" rubber runs in strategic place, that 80 was quite as a tomb lol.

The idea was to used different layers or materials that are "tuned" to different frequencies for best results. I recall having a substantial drop in dbs to the point that minor wind noises for rubber seals became suddenly very annoying lol.

Best of luck