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Cometic gaskets

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  #21  
Old 06-26-2018, 09:15 AM
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Originally Posted by shanechevelle
The gasket makes a "bead" where the metal is missing...

The head smashes down and where there are holes the gasket isnt compressed there, therefore it seals.

With our gaskets the material, coating, wears off and your left with a piece of metal anyway.
I need an interpreter. Anyone?
 
  #22  
Old 06-26-2018, 10:32 AM
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Cometic is only a better gasket. It isnt going to solve a head problem.

ARP studs are only better than stretch head bolts. They arent going to solve cracked blocks or slipped sleeves.




*i dont know that i would personally REuse a worn cometic gasket. I would, however, reuse old ARP studs
 
  #23  
Old 06-26-2018, 11:23 AM
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I would expect the Cometic to last longer.
Reason being, different materials expanding and contracting at different rates.
Cometic are all metal, and layers. Layers should allow faster cooling and less distortion.
More so, I would think that a composite gasket will fail sooner...because it's composite.
It is also metal, but coated. The coating expands and contracts differently than the metal it covers.
So, after however many heat cycles, miles, years, it is going to break down, and seperate from it's metal base.
Blowing the head gasket at the individual gasket's weakest point.
For whatever that's worth.
 
  #24  
Old 06-26-2018, 02:21 PM
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Another point they make is that less clamping force is needed to achieve the same sealing properties when compared to a paper gasket. This means less chance of stretching or stressing the block and distorting cylinder profile. With an aluminum block, this alone could make the cometic a better idea.
 
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  #25  
Old 06-26-2018, 04:23 PM
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Originally Posted by Fast951
I need an interpreter. Anyone?
I used small words...

Basically, where the metal is pressed together the gasket compresses, where there is no metal the gasket doesnt compress...thus forming a seal, bead etc.
 
  #26  
Old 06-27-2018, 05:40 AM
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Rappelez-vous

Try them and report back when 100K more miles is achieved, simples !

Nothing ventured nothing gained, better than keep chewing the fat about hypothetical theories and non comparable experiences.
 
  #27  
Old 07-17-2019, 03:40 PM
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Originally Posted by abran

Rover engineers might not be the brightest bulb in the chandelier, but they have more hands on experience with that specific motor than Buick did. And if Paul’s account holds water, it sounds like they had to make a change.

so, if Cometics are the best thing since sliced bread, why are we all running composites?

What other aluminum block & head engines run Cometics that are daily driver tasked, non high performance engines?
I'm going to have to make the choice of HG in a day or two most likely. I have put MANY cometic metal gaskets in my performance cars with great luck but I ask, why do you wish to quote only non high performance engines? My Honda S2000 is currently making 768whp out of 2.2 liters. I daily drive it and have for 75,000 miles of rather hard street and track miles and it's holding still. The Stock S2k motor is also composite. There was no other reasonable opotion for my daily driver S2K than cometic really. The S2ki forum WAS for over a decade the single largest car community in the world and online and there was almost NO discussion of any option besides cometic unless you went to specialist companies/ custom gaskets etc. Many were tried but one worked and worked consistently. ARP studs were considered the budget option for FI, serious 1000whp+ 2 liter builds would upgrade to FullBlown studs instead of ARP but they cost a fortune and I'm a prime example of ARPs properly installed holding 768whp for a long time of daily driving and serious abuse.

This Engine isn't an F22c though, so stories may differ here and of course I'm open to ideas but I did want throw in that my experience in a few other vehicles is that cometic is fantastic. Perhaps it's just a better option.
 
  #28  
Old 07-17-2019, 03:42 PM
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Originally Posted by Fastercat

Another option I’ve never heard of with the rover engines is to O-ring the heads. When I was heavy into drag racing it was all the rage for boosted applications. Machine a grove for the cylinders and water jackets, copper O-rings for the cylinders and rubber O-rings for the water jackets.
I built many high end sled motors with this system but the tolerance of head to cylinder was very tight. Also I never used sleeved cylinders, always nicasyl coated.
Not sure if it’s been tried on the rover v8.
The answer is here is, longevity.

Fellow sledder here with a Turbo M1000. For sale btw if twin 500cc two stroke turbos are your thing. Currently at 470hp.
 

Last edited by 05TurboS2K; 07-17-2019 at 03:50 PM.
  #29  
Old 07-17-2019, 03:45 PM
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Originally Posted by OffroadFrance
Raceline


To my knowledge, steel head gaskets have been around for circa 20-30 years in various uses and forms for mostly modern performance vehicles engines where the engines are regularly stripped down. When someone proves they have used steel head gaskets for 100K+ miles without any issues I'll be convinced
The S2K forum is FULL of guys with over 100k on cometic some of them in EXTREME hp numbers and commonly daily driven. I'm at 75k. Again though, it's different motor so it could be apples and oranges. One thing that might be worth thinking about it when it comes to surface area, cometic gaskets care less while a composite gasket suffers greatly because it relies on the entire surface for sealing.'

There's another interesting thing about cometic being that its all steel and the bead itself flexing is what provides a sealing surface, when a composite gasket fails, it blows out, this isn't true of a cometic. When a cometic fails it just allows leakage to occur but it doesn't mean it will worsen and no part of the gasket gives way causing catastrophic gasket failure. Now, failing is failing because it still will need to be replace but it COULD mean it fails in a very minor way and doesn't progress, this might equate to you making it home or continuing to drive it under failed conditions if you needed to. Perhaps that's advantageous enough for some?
 

Last edited by 05TurboS2K; 07-17-2019 at 03:55 PM.
  #30  
Old 07-17-2019, 03:56 PM
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Is there any folks here that can attest to success with cometic in the 4.0 and 4.6 motors? Anything but results is, simply speculation. I'm going to have to make a choice based upon the info and results found on this forum.
 


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