To insulate under the hood or not.

[tobyS]

My 929 that is excellent otherwise had wet insulation on the underside of the hood and made spots of rust on the inside of the hood. I removed it and it dried out and put the rust in check.

In north Indiana we can get rather cold, so not having insulation could be a problem.

I'll be refinishing the inside of this hood and don't want water issues. Previous rebuild trucks had a foam rubber that looked nice but how would one hold it in place.

What have you guys done.....wish I had bought a nos hood in gl days.

 

[Bill Nutting]

It was falling apart on my M934 so I removed it. I don't know what a 1/4" of foam rubber was supposed to insulate. Noise or cold temperatures. A 1/4" of foam rubber is completely useless for noise reduction and the engine makes it's own heat. I'm not replacing it. I might have an NOS one that came with the truck. If I find it, I will bring it to Findlay...

 

[tobyS]

It was falling apart on my M934 so I removed it. I don't know what a 1/4" of foam rubber was supposed to insulate. Noise or cold temperatures. A 1/4" of foam rubber is completely useless for noise reduction and the engine makes it's own heat. I'm not replacing it. I might have an NOS one that came with the truck. If I find it, I will bring it to Findlay...

Thanks bill, but I can't attach it and don't want to glue it on. A late RR rebuild had 1" foam that was real nice. Still, without spot welding on retainers ...maybe a chicken wire frame or some welded wire.

I don't want to put on something flammable either, like have urethane sprayed on.

 

[therooster2001]

I used new stuff, with the old nail then the original retainers. It sticks on one side. I posted it before. I’ll look. Worth it.

Edit: can’t find the manufacturer right now. 1” thick, Mylar on one side. $130 shipped to do the hood.

 

[therooster2001]

Close up of original retainers. Do you still have original “nail” in the hood?


Sent from my iPad using Tapatalk

 

[tobyS]

Those retainers are the biggest rust area and they fall apart when touched. Not useable in my case.

A place about 30 miles away makes rock wool board product with aluminum skin. . I'll do a dumpster dive...they throw a lot away.

 

[swiss]

I have had good luck with Dynamat. Both inside the hood and the cab. I do not understand the rusting issue as water does not get inside the hood?

Sound Absorption For Your Vehicles Engine Noise | Hoodliner | Dynamat

Dynamat Hoodliner is specifically built to absorb engine noise from your vehicles engine bay. Maximum noise control for maximum comfort.

www.dynamat.com

 

[glcaines]

I have an M35A3. It originally came with a steel hood and insulation secured with the round fasteners. The hood was severely rusted everywhere those fasteners were located. I replaced the old steel hood with an NOS fiberglass hood and no insulation. I couldn't tell any difference in the noise level.

 

[Bill Nutting]

I have had good luck with Dynamat. Both inside the hood and the cab. I do not understand the rusting issue as water does not get inside the hood?

Sound Absorption For Your Vehicles Engine Noise | Hoodliner | Dynamat

Dynamat Hoodliner is specifically built to absorb engine noise from your vehicles engine bay. Maximum noise control for maximum comfort.

www.dynamat.com

I use Dynamat in the cab. Do you hear a notable difference with it on the hood? I also put 1/2” horse trailer mat on the floor of the cab. That really brought the noise down.

 

[Karl kostman]

My 939 had foam type stuff under the hood when I bought it and it was not secure at all, it used those nail looking things with the big washer retainers I tore it all out and have never replaced it. I live in ND and it did not seem to make any difference what so ever in how the truck ran summer or winter!
On my Deuce to reduce noise I Rhino lined the floor up to where the cab top joins the tub and all to the way to the top of the floors in the front to where they end under the dash, then I used Dyno-mat over top the transmission under the cover in the cab. The rook inside I used 1" think tractor insulation. That took my truck from wearing ear plugs when driving down the highway to no ear plugs and can have a decent conversation in the cab without shouting at all.