Permatex Silicone

[kschachn]

After filling the cavities in the mounts with Gray Permatex, I'm finding that when you glob that stuff thick like that, the sealant towards the center has a hard time curing. On the outer edges it's curing just fine. But several days on, if I press an edge hard enough I can still get liquid gray permatex sealant to smear out. I'm wondering how long it will take to fully cure through and through (if it ever does).

It's gonna be interesting to see if that stuff withstands the pressures it'll be up against.

Yes those are likely acetic acid curing or some other method that requires off gassing. For very thick blocks of silicone that you want cured you need something with an added catalyst, such as a tin curing variety.

 

[The Critic]

After filling the cavities in the mounts with Gray Permatex, I'm finding that when you glob that stuff thick like that, the sealant towards the center has a hard time curing. On the outer edges it's curing just fine. But several days on, if I press an edge hard enough I can still get liquid gray permatex sealant to smear out. I'm wondering how long it will take to fully cure through and through (if it ever does).

Ultra Grey is just hot garbage. I know it’s a hot take, but I stand by this statement.

Try some Nissan RTV (1217H) or Hondabond HT; both cure very quickly and will dry rock hard.

 

[MaximumMini]

Ultra Grey is just hot garbage. I know it’s a hot take, but I stand by this statement.

Try some Nissan RTV (1217H) or Hondabond HT; both cure very quickly and will dry rock hard.

That might rule that out for this purpose? I need some give to absorb vibrations.
As far as the Ultra Gray. I don't doubt you. If it crumbles and falls out or cracks, oh well.
Now, I have used permatex ORANGE in some situations that actually held together FAR better than I ever expected under grueling conditions.
To the point that YEARS later when I wanted to remove it it was a significant challenge.
Maybe the Orange would have been better overall?

I'd love to find the right diameter and thickness solid inserts (also with the right size bolt hole) that I could press into the existing mounts. Not sure if they're made though.

 

[lbhsbz]

We used to just stuff the voids with chunks of fuel hose or vacuum hose or both until it was relatively solid.

 

[thastinger]

I need a good, load bearing silicone that when cured, will help assist support a heavy load. Temperature will always be below 250F. It will not be subject to immersion, oil, grease or fuel.

AFAIK, Once fully cured, the RED Permatex Silicone is the sturdiest, hardest, most dense of the Permatex line of Automotive Silicone Sealants.

I need a silicone that can support substantial weight load without failing. Do you know of a better silicone in a tube that would be a better load bearing silicone?

Let's forget the specific application. It'll be insides the engine compartment. Who cares? All that is important here is which is the best at supporting a heavy load.

Thanks if you have any information.

3M 1211

 

[kschachn]

The OP seems determined to use everything but what he needs. Here is the proper material although the required durometer isn’t really known. This is a platinum cured type of resin that will cure regardless of the cross sectional thickness. Any one-component resin such as an acetic acid or alcohol cured resin may never cure properly.

https://specialtyresin.com/products...MI08HwgYG4kAMVHyGtBh3qPgT_EAQYBCABEgJxzvD_BwE

 

[Arc]

Windshield Urethane...hmmmm...that is some good stuff. That just might be better.

Yes, I'm weary of the motor mounts sagging after just a few months of replacement and the engineer in me believes this simple adjustment might greatly extend their life. Looking at them, I would almost say they are made to fail sooner rather than later judging by the amount of material used for suspension and the design.

Too soft and it doesn't help. Too firm and you'll feel the vibrations. It's a balancing act.

Why not just buy new motor mounts or make a custom set? Motor mounts are easy to fabricate.

 

[MaximumMini]

Why not just buy new motor mounts or make a custom set? Motor mounts are easy to fabricate.

New motor mounts are usually junk...unless you pay BIG $$$ and buy from the dealership. Even then you might get cheapies for the astronomical OEM price.

Fabricating them......
If I had the right rubber compounds I could gut the old ones and make my own. Figuring out how to do the suspension material is the trick I spose. The Butyl used in windshield installation seems like a good candidate.

Or....I have a 20 ton press so if I could find some the exact same OD..Maybe from a V8 chassis that hold much more weight and press those into the existing mounts. I'd have to have a cylindrical press block made to the exact dimensions required tho ($$$)

 

[Arc]

New motor mounts are usually junk...unless you pay BIG $$$ and buy from the dealership. Even then you might get cheapies for the astronomical OEM price.

Fabricating them......
If I had the right rubber compounds I could gut the old ones and make my own. Figuring out how to do the suspension material is the trick I spose. The Butyl used in windshield installation seems like a good candidate.

Or....I have a 20 ton press so if I could find some the exact same OD..Maybe from a V8 chassis that hold much more weight and press those into the existing mounts. I'd have to have a cylindrical press block made to the exact dimensions required tho ($$$)

I ran a solid motor mount once and it actually worked pretty good. My brother did all the fabrication work for me when he was still on this earth. He was always building race cars, big trucks, working on heavy equipment etc. I remember he got big blocks of some kind of rubber compound all the time but I don't remember where, that was all before internet ordering. He was always stopping at factories picking up custom orders. Good luck on building your mounts, there is satisfaction in fabrication instead of just purchasing something.

 

[Exhaustgases]

The Butyl used in windshield installation seems like a good candidate.

Butyl is gooey and soft stuff. It is the windshield Urethane that you want it hardens up some but has flexibility, and unlike butyl heat and oil will not affect it. I like butyl for some things because it is easy to remove and clean off and seals okay.

 

[Arc]

Try a rubber track pad for equipment. Probably pick up a couple used ones at a national guard armory or equipment rental place.