achalmersman stroker 4.1 build (291 block)
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The reason I made sure everything was so flat was because I was going to show the whole Buick community how it was done. I was so sure that they would seal if everything was completely flat. In reality,the gaskets that Cometic says only leak when installed in an improper way (any way other than dry) leaked like a sieve when put on dry. Cometic warns that they might fail if any kind of coating is applied by the consumer. What a joke. The good news is that Cometics and Hylomar are an unbeatable combination.
achalmersman
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Lmao I can see myself going through that. I will learn from YOUR experience thank you very much lol. I still think I will probably put a smear of RTV in the top corners for oil, and maybe around the water ports
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It's amazing how my spellchecker needs spellchecking.I though I wrote how the cometics are not a slap on gasket hope you didn't think I though you went through all the prep work for no reason.
I highly recommend you do exactly what I did to ensure your surfaces are flat. Hylomar is untouched by antifreeze,water,oil,gasoline,and many other liquids. Both oil and coolant will seep through the layers if installed dry. Resist the urge to use silicone. Use only Hylomar. This is the national distributor for Hylomar.
http://www.silver-seal.com/product/HUBRA1/Hylomar-Universal-Jointing-Compound-69-oz-Aerosol.html
I knew what you meant.
Spray
That's the thing with MLS gaskets. The surfaces have to be FLAT and they HAVE to be smooth. Zero exceptions.
If anywhere on the head or deck has a 'mountain' that's a couple thou thick, that basically becomes a fulcrum with an unclamped load all the way around it. 99+% of the time it's going to hit water, a head bolt hole, or combustion. A nice squishy composite gasket that's .060+" thick can conform and absorb those nuances. Gaskets made of stainless sheet flat out cannot.
I've never used Hyloamr on MLSs but plain ole copper spray has gave me 100% success rate with new gaskets AND reusing Cometics as well. I do run a GM seal tab just for good measure.
Then again I use a GM seal tab on every cooling system I own, except my jet boat
If anywhere on the head or deck has a 'mountain' that's a couple thou thick, that basically becomes a fulcrum with an unclamped load all the way around it. 99+% of the time it's going to hit water, a head bolt hole, or combustion. A nice squishy composite gasket that's .060+" thick can conform and absorb those nuances. Gaskets made of stainless sheet flat out cannot.
I've never used Hyloamr on MLSs but plain ole copper spray has gave me 100% success rate with new gaskets AND reusing Cometics as well. I do run a GM seal tab just for good measure.
Then again I use a GM seal tab on every cooling system I own, except my jet boat
achalmersman
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No hijack offense taken. I encourage tech discussions in this thread
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Not really. Most engine builds are in an 'overlap' area where either will work. Only a MLS gasket HAS to have fully prepped surfaces. By 'prepped' I mean machined flat. Not belt sanded, not filed, not 'scraped smooth' with a razor blade... Machined flat and smooth. (Hand lapping counts and that's a machining operation). With a thick composite gasket, those things will seal on damn near anything.
So to loosely answer your question, composites will pretty much work anywhere. (If you're making so much power that a composite won't work, you already know what to use and how to use them). MLS gaskets can only work after prep is done.
You can go further with a MLS but if the heads and deck were machined by GM in the 80's, they'll probably leak on a 300hp stocker.
So to loosely answer your question, composites will pretty much work anywhere. (If you're making so much power that a composite won't work, you already know what to use and how to use them). MLS gaskets can only work after prep is done.
You can go further with a MLS but if the heads and deck were machined by GM in the 80's, they'll probably leak on a 300hp stocker.
achalmersman
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Well my block deck was machined to get it square but it's not a mirror finish. I can see the machine tool marks. I don't know what 50RA looks like but my heads are straight from Nick / porter and the deck is very smooth. What process would somebody use to try to finish lapp these surfaces? Would a long piece of glass do it with 800 grit and wd40? What's the process
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Can you snag a fingernail on the marks?
I used a diamond stone to highlight any tool marks. Draw a line across the surface with a sharpie and hit it was a stone or some glass. Whatever marks are left will look waaaaay worse than they really are. You'll probably die of old age using WD and 800 grit.
I did have a slight advantage since I was doing the machining myself so I was able to screw with feed and speed while I was shaving.
I used a diamond stone to highlight any tool marks. Draw a line across the surface with a sharpie and hit it was a stone or some glass. Whatever marks are left will look waaaaay worse than they really are. You'll probably die of old age using WD and 800 grit.
I did have a slight advantage since I was doing the machining myself so I was able to screw with feed and speed while I was shaving.
I wasn't planning to get my block decked, but I know my heads have been ported in polished previously about 5k miles ago along with an intake, so I wasn't planned to resurface anything. But I guess I'll have to talk to my machinist and see if he thinks it needs it or not.
The one I described.
It doesn't matter what he thinks. You need prove that your decks are flat. The processes that I described will tell you what you need to know and will create the smooth flat surface you need to use Cometics. There is nothing,above and beyond what you've done,that you need to do to get a good seal with composite gaskets.
achalmersman
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What if I don't have access to a special piece of steel that so know is perfectly flat? Is glass a no-no or not flat enough?
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achalmersman
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Without flash
With flash
Snag a fingernail...no, but going against the tool marks you can feel the "vibration". My heads feel like glass going across them with my fingernail. I'm guessing the block deck isn't good enough.
No trees were harmed in the sending of this message, however, a significant number of electrons were terribly inconvenienced.
Edit: pictures suck because website is compressing the hell out of the file.
With flash
Snag a fingernail...no, but going against the tool marks you can feel the "vibration". My heads feel like glass going across them with my fingernail. I'm guessing the block deck isn't good enough.
No trees were harmed in the sending of this message, however, a significant number of electrons were terribly inconvenienced.
Edit: pictures suck because website is compressing the hell out of the file.
