Cometic MLS head gasket and Hylomar

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cjperformance
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Re: Cometic MLS head gasket and Hylomar

Post by cjperformance »

mk e wrote: Mon Oct 22, 2018 3:20 pm
cjperformance wrote: Mon Oct 22, 2018 3:10 pm
Mark, yes correct on the aviation over the long time span, it does eventually degrade and turn to that dusty crust for sure.
I've never tried 518 on a head gasket, that said I'm sure it would be perfectly its very good stuff.
I wonder how that will go long term, 10/15 years?
I've not tried 518 on a head gasket....I've been scared about the film thickness. The aviation sealer torques out really thin but 518....a few thou is about as thin as it gets I think. I use it on just about everything else and have been using it since the mid 90s....everything I've ever torn apart has looked good.....it does get a little brown where it was hot but still seemed to be flexible and sealed.
Good point re film thickness, I've used 518 on intakes like ford Cleveland with the metal pan gasket and removed them and it squeezes out to pretty much nothing but thats a thin flange point. Head gasket area could be a different story! Like when i have removed copper gaskets that someone has used 3bond on, you can scrape a thin layer of 3 bond from almost everywhere apart from around where the head bolt goes thru, it definitely leaves a thin layer , not good.
I'll keep the 518 for experimenting on a personal copper gasket 1st !
Craig.
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Re: Cometic MLS head gasket and Hylomar

Post by BradH »

Can I jump in here w/ a question? I found after the dyno session that the Mr. Gasket coated MLS gaskets I used when I reassembled my BB Mopar leaked water... :( I've since heard some other complaints about the Mr. Gasket MLS stuff, since they're no longer simply re-packaging Cometics as I believe the did originally.

I've bought a set of Cometics in the same bore size & thickness to replace them. "Once burned, twice shy", so I've also purchased the Mopar spray sealant the ChryCo dealers were instructed to use when changing out defective composition head gaskets for then-new MLS gaskets back in the '90s

What's the best approach to apply this sealant to be effective against water passage leaks without having excessive sealant on the head & block mating surface and avoiding sealant being squeezed into the chamber? Thanks - Brad
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Re: Cometic MLS head gasket and Hylomar

Post by Cubic_Cleveland »

BradH wrote: Thu Oct 25, 2018 2:54 pm Can I jump in here w/ a question? I found after the dyno session that the Mr. Gasket coated MLS gaskets I used when I reassembled my BB Mopar leaked water... :( I've since heard some other complaints about the Mr. Gasket MLS stuff, since they're no longer simply re-packaging Cometics as I believe the did originally.

I've bought a set of Cometics in the same bore size & thickness to replace them. "Once burned, twice shy", so I've also purchased the Mopar spray sealant the ChryCo dealers were instructed to use when changing out defective composition head gaskets for then-new MLS gaskets back in the '90s

What's the best approach to apply this sealant to be effective against water passage leaks without having excessive sealant on the head & block mating surface and avoiding sealant being squeezed into the chamber? Thanks - Brad
I’ve never used it (or heard of it down here), but I assume it’s similar to Hylomar spray? For Hylomar I hang the gasket from a piece of wire and spray a thin even coat on both sides. Let it tack off and assemble.

On disassembly I’ve never noticed it creep into the chambers, but I only use a thin coat and spray in a random manor, unlike painting a panel..
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