Hey Mike, its Trent. That set I bought a few weeks back is an old set a member had sitting on his shelf, so no telling how old they are. The set I got from Cruz up at RC's in NC came in a very different packaging. Wish I still had those gaskets to look at them.
Cometic HG design
- Thread starter Mike T
- Start date
Hey Mike, its Trent. That set I bought a few weeks back is an old set a member had sitting on his shelf, so no telling how old they are. The set I got from Cruz up at RC's in NC came in a very different packaging. Wish I still had those gaskets to look at them.
Mike T
Well-Known Member
- Joined
- May 3, 2013
Thanks for the photo and thank you for clearing that up, was really starting to wonder what to heck was going on.
A smear of "Yamabond'' around the water ports on deck and heads, and copper coat on all 6 sides of the gasket (filleted open) will seal like the heads and block are one item.
That's assUming the surfaces are FLAT and SMOOTH. And by 'flat' I mean machined or ground flat, not 'equally shiny all over from a ziz wheel'.
That's assUming the surfaces are FLAT and SMOOTH. And by 'flat' I mean machined or ground flat, not 'equally shiny all over from a ziz wheel'.
I've heard to do the same (copper coating) and I've heard not to..... I've done cometics all types of ways and it seems as long as the decks are clean and smooth like you say I don't ever have a problem. Although I will say I have never gone completely dry, always have had some sort of sealant around the oil returns.
Seems like there's a few ways to skin this cat, but I lean to having something on there to help.
I don't blame Cometic for saying not to fillet them and spray them. From their point of view they have no control over the end user screwing up the gasket by accident.
and I'm SURE they wouldn't like the idea of reusing one of their gaskets....
...like I'm currently doing. When I pulled the heads off my 4.1 to install my forged pistons I cleaned the gaskets, resprayed them and put them right back on.
and I'm SURE they wouldn't like the idea of reusing one of their gaskets....
...like I'm currently doing. When I pulled the heads off my 4.1 to install my forged pistons I cleaned the gaskets, resprayed them and put them right back on.
Mike T
Well-Known Member
- Joined
- May 3, 2013
Yes, I agree there are many ways to achieve a leak free seal. My case is a little different because the HG's are somewhat custom to my block and heads. A lot of time was spent reshaping areas of the gasket that were slightly hanging into the combustion chamber. For this reason I didn't put additional sealers on the gasket because intended to reuse them in the future and wanted to avoid trying to remove RVT ext. from them.
Bet the new ones will work dry as they have been recommending, particularly if they have improved the viton coverage as Rob has observed.
Bet the new ones will work dry as they have been recommending, particularly if they have improved the viton coverage as Rob has observed.
No disintegrations
Well-Known Member
- Joined
- Dec 27, 2015
Why wouldn't cometic or whoever made them just add the black coating to every side of the sandwich? To save 5 cents I think.
- Joined
- Feb 18, 2006
There is. It's called "viton" which is synthetic rubber. When people spray shit and put a smear of that around water ports they are doing more harm than good....
No disintegrations
Well-Known Member
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- Dec 27, 2015
Gotcha. For some reason I remember it not being on the inner layers.
i just got a set of cometic .040 gaskets for GN1 aluminum heads and roller cam goodies. The intention was to install these on my all original unopened engine. I asked vendor if I needed to deck block and they said no, clean it well and install them dry. Do you guys agree with this? What are the "prep steps" that I need to know about? I don't want to do the job twice. Thanks.
When I got home from work I can post a picture to see what they look like compared to the ones you guys have.
When I got home from work I can post a picture to see what they look like compared to the ones you guys have.
SCOOBY DOO
BASED CANADIAN PATRIOT!!
- Joined
- Feb 18, 2007
Cometic Technical Support-How To Install Cometic Head Gaskets
http://www.cometic.com/ft-2800-technical-support.html
http://www.cometic.com/ft-2800-technical-support.html
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Check your breather if you run them. They can drip and it can run off the valve cover and look like a leak.
Step one is to deck the block. During the decking process, make sure to bevel the hell out of the head bolt holes.
While the surfacing machine is running (and you're 'one with the machine') make sure your last pass leaves a SMOOTH SMOOTH SMOOTH finish. Then hit it with a diamond stone to make sure it's as SMOOTH SMOOTH SMOOTH as possible
NOTE: When I say 'surfacing machine' I DO NOT mean belt sander!!!!!
There's a few more steps, but you have a 30+ year old block that's not freshly machined (and when it was machined decades ago, it was machined for thick ass composites)
...so basically, don't listen to your vendor. MLSs are not for you with what you have going on.
- Joined
- Feb 18, 2006
I think you can get away without resurfacing but that's my opinion.
Clean and dry. Prep the mating surfaces with lacquer thinner then use low pressure compressed air to blow off any particles of dust and lint.
A important and often overlooked step is to chase and clean the head bolt threads then seal in
the new studs. I prefer blue loctite gel. This will ensure there will be no coolant leaks. After you chase the threads, use brake cleaner to douche the hole then compressed air to dry them out. New head studs also need to be cleaned with lacquer thinner. Clean clean clean. That's the ticket.
Once the heads are mounted and torqued I like to run a bead of black RTV on the front and back seam to help prevent oil leaks.
This procedure has had a 100% success rate for me.
I've machined enough heads and blocks to NEVER try an MLS on a 30 year old surface.
As the machine runs, you can see the 'islands' that are clean and the dirty low areas. They're always between cylinders or go from the combustion chamber to a water port. The high spots like to be at the head bolt holes. That alone is almost a deal breaker. If the clamping point is a few thou high, you just lost a LOT of clamping pressure between the head bolt/studs.
Not to mention the 'sawtooth' finish you get from knocking down the high spots from an aggressive cut with a high feed speed. Thin stainless steel just can't marry to those kinds of surfaces. ESP with only four clamping points per cylinder.
I'd never try it but If I did, I would REALLY be impressed with the black goo and/or copper coat.
Here's a good example of a factory GM finish (plus warpage from being torqued down)
With a thin steel intake gasket I might have had trouble with this manifold.
This was probably the ''flattest'' 8445 head I ever skimmed. It came off a low mile N/A regal I found crashed in the junkyard. It does have a little twist to it though
As the machine runs, you can see the 'islands' that are clean and the dirty low areas. They're always between cylinders or go from the combustion chamber to a water port. The high spots like to be at the head bolt holes. That alone is almost a deal breaker. If the clamping point is a few thou high, you just lost a LOT of clamping pressure between the head bolt/studs.
Not to mention the 'sawtooth' finish you get from knocking down the high spots from an aggressive cut with a high feed speed. Thin stainless steel just can't marry to those kinds of surfaces. ESP with only four clamping points per cylinder.
I'd never try it but If I did, I would REALLY be impressed with the black goo and/or copper coat.
Here's a good example of a factory GM finish (plus warpage from being torqued down)
With a thin steel intake gasket I might have had trouble with this manifold.
This was probably the ''flattest'' 8445 head I ever skimmed. It came off a low mile N/A regal I found crashed in the junkyard. It does have a little twist to it though
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