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Old 04-28-18, 07:58PM   #1
SloBird
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Default Will Cometic head gaskets seal where others fail?

I first assembled 400 late 2012 with Fel-Pro perma-torques, new turbo setup in 2013 averaging 12psi. Those gaskets lasted till Nov 2017, freshened up motor during winter using Fel-Pro black perf 1016 head gaskets. They lasted 3 days of test & tune averaging 6-8 runs per day. Both times head gasket pushing combustion sealing bead at #5 cyl to steam hole. I purchased Cometics from Butler, pulled heads today to install. Checked deck with straight edge, block above #5 has .002" low area between steam holes.

Will Cometics seal with .002" low spot? Do Cometics need a certain surface finish on block & heads? Thanks
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Old 04-28-18, 08:02PM   #2
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Quote:
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I first assembled 400 late 2012 with Fel-Pro perma-torques, new turbo setup in 2013 averaging 12psi. Those gaskets lasted till Nov 2017, freshened up motor during winter using Fel-Pro black perf 1016 head gaskets. They lasted 3 days of test & tune averaging 6-8 runs per day. Both times head gasket fail at #5 cyl to steam hole. I purchased Cometics from Butler, pulled heads today to install. Checked deck with straight edge, block above #5 has .002" low area between steam holes.

Will Cometics seal with .002" low spot? Do Cometics need a certain surface finish on block & heads? Thanks
cometics need a ra50 or smoother.
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Old 04-28-18, 08:16PM   #3
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cometics need a ra50 or smoother.
What do you use to get ra50? I'm used to using those scotch brite type rotary pads on hi speed air tool, use them on everything automotive where there's a gasket.

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Old 04-28-18, 09:49PM   #4
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Default Recently new Fel-Pro 1016

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What do you use to get ra50? I'm used to using those scotch brite type rotary pads on hi speed air tool, use them on everything automotive where there's a gasket.
Previous Fel-Pro 8518 failed the same, but lasted 4 yrs + with many days of racing
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Old 04-28-18, 09:56PM   #5
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When I send my heads and block to the machine shop I tell them RA 50. It is a real smooth mill.
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Old 04-28-18, 10:03PM   #6
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When I send my heads and block to the machine shop I tell them RA 50. It is a real smooth mill.
Thanks
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Old 04-28-18, 10:27PM   #7
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Cometics...definitely a better gasket. Just make sure to line up water holes with gasket just to make sure thereís enough gasket material to seal around the holes. Canít tell you if it will solve the .002 dip and will seal better or not. But you can resuse the Cometics over. Good luck
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Old 04-29-18, 01:39AM   #8
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Guys have used a product from hylomar with good results and I’ve used HI Tack by 3 m which I also use on my ( radials to rim to keep them from spinning on the rim instead of screws) it’s really just to seal for the water the cyl seals quite fine without the ra50 IMO

Most guys I know do not finish to ra50 and my head gaskets have only failed once and it was because they were burned by a header leak. That’s another story though. Just watch for interference where the gasket hangs out and the header may meet up with it.

There’s a thread here about the hylomar product but not sure they still make it. One of our members worked there of I remember correctly. Thats probably going back to 2009 or 2010 though.

Keep in mind I run iron block iron heads though, most people’s regorque issues come from Ron block alluminum head configurations. Diffferences in thermal expansion and contraction rates.
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Old 04-29-18, 03:08AM   #9
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Before I went to cometic, I use to spray both sides with copper coat worked real good.
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Old 05-02-18, 12:11AM   #10
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Default Putting Cometics coated with Hylomar

Just got my heads back from machine shop, had them take a light - smooth cut. Don't know what "ra" finish, but a lot smoother, block was smooth already. I read up on old thread from this site, convinced me to go Hylomar over copper-coat. Thanks for your advice Turbo69Bird.

http://www.pontiaczone.com/forum/sho...hlight=hylomar

I do love the boost though
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Old 05-02-18, 01:14AM   #11
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Hope it works for you
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Old 05-02-18, 10:52AM   #12
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Cometic people will tell you not to put anything on there gasket. Just dry, thats what i do . If theres a problem with leaking its because of something else...
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Old 05-02-18, 11:39AM   #13
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Iíve got some good pics of some failed cosmetics for those who think they are infallible.

That being said I run cosmetics still, but they arenít the be all end all by any means. Some cosmetics with a coating would be the way to go. Especially a self healing coating.
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Old 05-02-18, 11:41AM   #14
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. As flanges sealed with Hylomar Universal Blue are pulled apart, the material stretches, and then breaks cohesively, leaving sealant on both sides. When the flanges return together, the putty reseals, a self-healing mechanism. This makes Universal Blue a particularly effective sealant on close fitting large flanges which are subject to extreme vibration, distorition, or joint movement, because while the seal may break for a microsecond, it reseals and the fluids remain contained.


Keep in mind I am talking about sealing water withe the cosmetics, that’s it’s issue. Sealing the cylinders has not really been an issue with cosmetics for me. Except when they were burned by an exhaust leak caused by the cosmetic extending too far out and interfering with the exhaust flange being torqued tight against the flange.
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Old 05-02-18, 11:49AM   #15
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Quote:
Originally Posted by SloBird View Post
Just got my heads back from machine shop, had them take a light - smooth cut. Don't know what "ra" finish, but a lot smoother, block was smooth already. I read up on old thread from this site, convinced me to go Hylomar over copper-coat. Thanks for your advice Turbo69Bird.

http://www.pontiaczone.com/forum/sho...hlight=hylomar

I do love the boost though
Youíre welcome, I hope it works out for you now. people who use I swear by it.
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