Hood insulation: Why? Do you keep it, or don't you?

[LT7A]

I've had some vehicles with hood insulation and some without. From a high performance mindset, I can't see how it would help. Unless you live way up north in Coldlandia or Coldaska and have a hard time maintaining operating temperature, I don't see how there's a benefit except at initial startup/warmup. I can more easily make a case that it's there just to suppress sound. We all know that NVH is really important to the manufacturers. I would imagine that quiet seems smooth, and smooth + quiet probably help sell vehicles on test drives. Once up to operating temperature, it seems that any insulation would have a negative effect on performance. There is a lot of air going over the top of the hood that could draw heat out of the engine compartment. The closest thing to the hood is typically where the air and fuel are being drawn in. Any drop in temperature in that area sure seems like it would be a performance gain however minimal.

I'm considering pulling the hood insulation out of all of my rigs. I don't mind hearing the motor when it's doing its job. And generally speaking, if it's not revving up, then I don't think it's going to transmit much noise through the hood through the windshield and into the cabin. And I don't mind startling innocent bystanders and woodland creatures when I drive by. What do you guys think: Keep it, add it, toss it?

[Bandit130]

You are referring to the under side of the hood? I don't think it is necessarily insulation. From what I was told years ago, it is held up by plastic clips. Designed in the event of engine fire, clips will melt and it will fall down on engine to help smother fire.

I believe this is correct but someone else may know the original purpose if not for a fire.

[mongocanfly]

^^^^never heard that before^^^^
Keith....what say you?

[langss]

Not that it has made a difference with the longevity of the paint on the hood of my truck, but that is the reason I have been told that all the Mfg started insulating under the hoods. I remember the plastic retainers were supposed to melt and drop the insulation, but I think that would just make it harder to put out any fire. If it in good condition, I would leave it. If its shredded up like the one in my truck, maybe say goodby.

[Bluestep]

I have always assumed it is for sound dampening, as it was included only in the more upscale trim packages.
I have never heard the fire suppression theory. I don't buy it. If that was the case it would seem that all trucks would have had it. As for the plastic retainers, they are just the most logical fastener for function and ease and speed of assembly.
I do not have one on my pickup. I painted the underside of the hood so that it looks fine without it and the sound of the engine is pleasing to me.

[langss]

Originally Posted by Bluestep

I have always assumed it is for sound dampening, as it was included only in the more upscale trim packages.
I have never heard the fire suppression theory. I don't buy it. If that was the case it would seem that all trucks would have had it. As for the plastic retainers, they are just the most logical fastener for function and ease and speed of assembly.
I do not have one on my pickup. I painted the underside of the hood so that it looks fine without it and the sound of the engine is pleasing to me.

I'll go with your analysis. Like I said above, it did nothing for the paint, and I would not want to be a Fireman trying to lift that thing up to shoot an extinguisher under it.

[LT7A]

Interesting! I had not thought of the fire suppression possibility. The only engine fire I've ever had to put out was low on the motor and feeding off of the accumulated oil leak build up. That was on the motorhome of somebody I didn't know along the highway. Curious, did the Cheyenne or Scottsdale trucks have hood insulation?

[langss]

Originally Posted by LT7A

Interesting! I had not thought of the fire suppression possibility. The only engine fire I've ever had to put out was low on the motor and feeding off of the accumulated oil leak build up. That was on the motorhome of somebody I didn't know along the highway. Curious, did the Cheyenne or Scottsdale trucks have hood insulation?

I have been to a lot of wrecking yards over the years and I have never seen any square body without the insulation. True many(like the one in my truck)were thrashed and hanging down, but regardless the remains were always there. So it may have been an option, that was part of another package.... Who knows today.

[Bluestep]

Originally Posted by langss

I have been to a lot of wrecking yards over the years and I have never seen any square body without the insulation. True many(like the one in my truck)were thrashed and hanging down, but regardless the remains were always there. So it may have been an option, that was part of another package.... Who knows today.

Langss, here is a link to the GM Heritage Center
https://gmheritagecenter.com/gm-heri...tion-kits.html
You can look up your model year of pickup (or any other) and can read about how the different models were equipped. It is very well documented from the time the trucks were built. No guessing, conjecture or assumptions.

[langss]

Originally Posted by Bluestep

Langss, here is a link to the GM Heritage Center
https://gmheritagecenter.com/gm-heri...tion-kits.html
You can look up your model year of pickup (or any other) and can read about how the different models were equipped. It is very well documented from the time the trucks were built. No guessing, conjecture or assumptions.

Thank You for the information.

[abig84]

Originally Posted by langss

I have been to a lot of wrecking yards over the years and I have never seen any square body without the insulation. True many(like the one in my truck)were thrashed and hanging down, but regardless the remains were always there. So it may have been an option, that was part of another package.... Who knows today.

Interesting, I personally have never owned or seen a square with it. I've never had it and never had any over or under hearing issues

[100%Chevy]

I bought a new 80,C-20 Custom Deluxe and it didn't have the hood blanket.
The new 82,K-10 Silverado I bought has a hood blanket.(still have the truck)
So,maybe it's a Silverado thing?
And,I have had underhood fires with no damage to the paint,possibly because it has the blanket.Not big fires either.
My 65 Impala has one and is held up with steel clips.
Mike.

[mongocanfly]

my 81 custom deluxe had it so its not just a silverado thang...

[bennylava]

My main concern, and the reason I keep mine, is sound deadening. Exhaust may sound cool, but engine noise is just annoying. Here's a better one I want to get someday:

https://www.amazon.com/FatMat-Hood-L.../dp/B00H6X4V7C

[langss]

Thank You for that link. When I get back to working on my truck, I will have some of that to replace what's already shredded, and all the little plastic retainers that have started to just fall away.

[mongocanfly]

I know mine came off ebay and I think this is where I got it...looks great,,, fit perfect.....https://www.ebay.com/itm/1981-1987-C...dV1K-F&vxp=mtr

[stanski]

Definitely have to call BS on the fire suppression theory. Underhood pads were available on some cars as far back as the 50's. They were there to suppress engine noise and improve interior comfort. Prior to the age of plastics they all had metal retainers and rods, I think by the time those melted and released the blanket, the fire would have burned itself out.

[nascarmikeb]

'86 Sierra Classic, I have the blanket as well.

[hatzie]

It's for noise suppression. It was stock on the higher trims and optional on the lower trims. You could pick N choose your options back then, unlike today.

It's part of the 16.5 Insulation and Deadener group in the 79-84 parts books... There are a lot of different deadener and insulation pieces referencing floor and engine. I assume deadener means sound-deadener.

[Keith Seymore]

It was part of the uplevel trim packages, like Cheyenne and Silverado. That's why you don't find it on the lower trim levels, like Custom Deluxe or Scottsdale.

It was primary to control radiated underhood noise. That's why it was also part of the Diesel Prep package.

It was made of a flame retardant material, which is perhaps where they understanding came from that it would smother an underhood fire. It certainly would not be prudent to make it out of some type of flammable material.

K

[Keith Seymore]

Originally Posted by mongocanfly

my 81 custom deluxe had it so its not just a silverado thang...

Nope.

Either somebody added the insulator, swapped hoods, or it was a factory mistake, but it is not part of the Custom Deluxe trim level.

K

[hatzie]

I made an assumption that it could be optioned on the lower trims because I had two mid-80's Custom Deluxe trucks that came to me with that pad on the bottom of the hood.
Prolly the PO just installed it. Not like it's a super tough thing to do.

[mongocanfly]

Keith I know anythings possible....mine came from a fire dept...always stored inside...never wrecked...with 20200 miles on it...I just assumed it was original...
and I mistakenly said mine was a custom deluxe but mines a Scottsdale. ...
ye9 is not on my spid if thats the deadner code....

[hatzie]

YE9 is the top trim package RPO.

GM likes to recycle RPOs and Trim package names.

1973-1974

Base model - Chevy Custom/GMC Custom
Z62 - Chevy Custom Deluxe/GMC Super Custom
Z84 - Chevy Cheyenne/GMC Sierra
YE9 - Chevy Cheyenne Super/GMC Sierra Grande


1975-1981

Base model - Chevy Custom Deluxe/GMC Sierra
Z62 - Chevy Scottsdale/GMC Sierra Grande
Z84 - Chevy Cheyenne/GMC High Sierra
YE9 - Chevy Silverado/GMC Sierra Classic


1982-1987

Base model - Chevy Custom Deluxe/GMC Sierra
Z62 - Chevy Scottsdale/GMC High Sierra (Note this change)
Z84 - Discontinued
YE9 - Chevy Silverado/GMC Sierra Classic

http://www.73-87.com/7387info/7387trimlev.htm

[wazzabie]

I know for a fact that the hood blanket was included from factory in custom deluxe.