M35A3 underhood insulation rivets - size?

Potluckslammy

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Anybody know the dimensions for this little gem? All the black coating has cracked and blow off the insulation blanket, which I would like to take off and recoat. And there is rust-through beginning to show on the split steel hood, which will need repair.
I have the part number for the rivet, which is 12448964. Doing a search, it shows up in some aerospace parts houses, but only option is to request a quote. Also, yes I know they're available as N.O.S. from one of the MV parts suppliers...but $1 a piece makes my butt cheeks clench!
Figured something suitable can be sourced from some place like McMaster if I could get a measurement. Suppose if worse comes to worse I'll just have to cut one off and measure it. 😓
 
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Potluckslammy

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I'd get a single $1 rivet if you can and measure that to figure out a common rivet to use.

I saw a pack of 10 on EBay for $10 after a quick look. It might be a small additional price to pay to get your job done.
Yes, only available in packs of 10, so far as I can tell. Guess I need to stop being lazy, and just get to cutting! 😅
 

Potluckslammy

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Also, I plugged that number into a search engine and came up with a place called Rivets on Line. Was way cheaper the flea bay.
Yes! Excellent info! Looks like that's JC Sales, which comes up as a parts supplier in other search hits. Much better price, and best of all they list the measurements I was looking for:

  • Tubular Component Diam.: 3/16
  • Grip Range: 7/8 to 1-1/16
  • Head Diameter: 3/8
  • Material: All Steel
  • L1 Rivet Length (Max.): 0.53
  • L2 Component Length (Max.): 0.825
Thanks so much!
 

Potluckslammy

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How do you plan on re-coating the insulation? The coating on my hood and side panels is coming off too, little by little.
That's a good question, glad you asked! Well...I used some flex seal on a pair of insulated pack boots one time to waterproof. Worked ok, except it cracked pretty soon in the creases and folds where the fabric flexed. But I figure the insulation blanket doesn't flex, so it should be ok. Alternately, I thought about using some roll-on bed liner. The mat is porous, so it should adhere ok.
I'll try the back side first to see what happens. And I have two trucks to play with, so the worse of the two gets it first. Wash and dry the mats, spray the coating. Then flex it a bit after drying. Will be sure to post a write-up to share the results!
Also, another thing that goes with this topic is the subject of what to do with those retaining washers. They're pretty rusted, too! And while replacements are also available, I'll likely refinish the old ones. Rattle can paint would be ok, but these will likely be powder coated. Unfortunately, a bead blast cabinet isn't available, so something else will have to be worked out to clean them.
 

HDN

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I'm wondering if heat-resistant paint for the washers should be considered. The engine compartment probably gets up to about 200 degrees Fahrenheit, and I'm not sure how well regular automotive paint would hold up to that.
 

Potluckslammy

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I'm wondering if heat-resistant paint for the washers should be considered.
That's a good point. Pretty sure rattle can is good up to 200. I've used it for touching up automotive applications that get at least that hot. Have some tractor/implement paint in CAT yellow I'm going to use to touch up the valve cover...and the camo green I used on the thermostat housing and coolant pipe are holding up well.
If it were closer to the turbo or exhaust manifold a high heat coating would definitely be in order! But for these heat shield washers the powder coat I have planned will work well, and be more durable than paint. It's good up to minimum 400 degrees with no degradation. The application process is pretty easy, too, for small parts...assuming I get all the rust off!
 

glcaines

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I trashed all of that insulation under my steel hood. I plan on trashing the insulation on the side panels as well but haven't yet. That insulation causes rust if you have a steel hood. I located an NOS fiberglass hood years ago and it is far superior to the cut and widened steel hood that rusts no matter what you do. After getting rid of the insulation when I still had the steel hood installed, I couldn't tell any difference in sound in the cab. I actually have an NOS side panel for the drivers side and have planned on installing it for years and never got around to it. If it was me, I would look for an inexpensive fiberglass hood. They look substantially better and don't rust. If you do keep insulation, I would buy a length of new insulation material and forget trying to re-coat the old stuff. M35A3s produced in mid-1998 had the fiberglass hoods from the factory. Mine is a 1998 but was a few serial numbers shy of when they switched to fiberglass. I can't remember the S/N where they switched.
 

Potluckslammy

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I trashed all of that insulation under my steel hood....They (fiberglass hood) look substantially better and don't rust.
Agreed! My 99 has a fiberglass hood, and it's ok. Weighs about the same as the steel hood. Unfortunately, somebody busted off the corner hold-down...and tried to fix it with Bondo! So have some glass repair to look forward to... 😏 IMG_20220401_182556_277_copy_1200x1600.jpg Last I checked a N.O.S. fiberglass is about $800! So I'm just going to keep the steel hood on the '93. Will roll some bed liner on the underside after the rust is cleaned and repaired..should prevent any further issues in that regard.
 
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Potluckslammy

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Took a look at the situation today on both a steel hood, and a fiberglass. The steel will be easy-peasy...just drill out the old rivet, pop on a new one. And luckily most of the washers are in much better shape than I remembered:
IMG_20220401_170526_907_copy_1200x1600.jpg
All except for the bottom washers on the side panels, some of which were so far gone they fell off!
IMG_20220401_170547_200_copy_1200x1600.jpg
Discovered too late that the fiberglass hood uses a different attachment arrangement, so this is a VERY IMPORTANT nugget of information to include! The studs that hold the washers on are GLUED ON to the hood! They use a "push-on" type of fastener to hold the washer! Tried unscrewing the thing...pushing down and twisting, too...no joy. So got a claw hammer and tried prying the cap off! Wound up ripping the whole stud loose from the hood, and having to cut it after the fact! 😬
IMG_20220401_172326_090_copy_1200x1600.jpg
IMG_20220401_172336_935_copy_1200x1600.jpg
So don't do that! Looks like it may be possible to push the tabs open from underneath with a pick, or probe. I'll update a success or failure when the chance to try it comes up.
 

glcaines

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No photos of tearing out the insulation. My steel hood was so rusted under the insulation I simply took it to the transfer station for recycling. I believe the problem is that water leaks past the seams on the center piece of steel on top of the steel hoods and soaks the insulation with water which is held in and can't easily evaporate, rusting out the underside of the hood. One thing I found out is that there are two different designs for the fiberglass hoods. Mine has the scalloped edges on top, where some don't have this. I do know there were two different manufacturers. I know also that some aftermarket fiberglass hoods were available. I believe I paid $125.00 for my fiberglass hood, or something similar, but this was years ago.

M35A3 Front.jpg
 

HDN

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I brought my truck out of hibernation today. While checking the engine compartment fluids, I paid special attention to the underside of my truck's hood. Through an oddly-placed hole in the insulation, it looks like it had some black coating applied before the insulation was installed. As the hood was sitting in the upright position, I noticed water starting to drain from between the insulation and the rear edge of the hood. I also noticed a bit of rust along the hood nose's edge.

I think the next time I paint the truck I'm going to try to find a fiberglass hood that'll fit. If not, maybe I can find someone to make one for me.
 

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glcaines

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I brought my truck out of hibernation today. While checking the engine compartment fluids, I paid special attention to the underside of my truck's hood. Through an oddly-placed hole in the insulation, it looks like it had some black coating applied before the insulation was installed. As the hood was sitting in the upright position, I noticed water starting to drain from between the insulation and the rear edge of the hood. I also noticed a bit of rust along the hood nose's edge.
I think the next time I paint the truck I'm going to try to find a fiberglass hood that'll fit. If not, maybe I can find someone to make one for me.
You will love a fiberglass hood. They used to be fairly common, but are scarce to find now.
 

HDN

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I'll try to get pictures later today since I don't actually have any pictures of the top of my truck's hood! Usually any time I'm up there the hood's up, and I can't usually see the top of the hood unless I'm driving since my truck's hood is a few inches higher than the top of my head :p What I can tell you is that M35A2 hoods were cut down the middle and widened with sheet metal riveted to the halves. The hood was also lengthened with sheet metal riveted to the back edge of the old hood halves.

Later production M35A3 trucks than mine had 1-piece fiberglass hoods. I don't know at what point AM General started using those. I imagine an industrial engineer at the plant told their manager that the modified steel hoods were a PITA and that fiberglass was better for longevity and probably for cost of production.
 
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