Cometic gaskets
 

Just received my first set of cometic head gaskets. Quite a departure form the fel-pro gaskets I have been using for years now.

Any tips on the best usage or any pitfalls to avoid? I assume everything is the same as far as installation. I have been told they don't need to be re-torqued

Re: Cometic gaskets
 

Just torque them down and forget they are there. They wont fail.

Re: Cometic gaskets
 

that is what is what I hoped to hear. Just hard to wrap my mind around the loose layers at the bore's edge :D

Re: Cometic gaskets
 

Haven't used them on my boat motors but used to use that brand on all my race motors in my jet skis. Had more in those than in the small blocks in the scarab. Just as here money wins every time. They definatly were different than oem but never a problem on my 2 strokes.

Re: Cometic gaskets
 

To look at them , you would wonder how they seal but I've used them in a number of engines with both steel and aluminum heads and never a problem :D

Re: Cometic gaskets
 

They were the answer with my Procharged motor. No problems since.

Re: Cometic gaskets
 

Can they be re-used after the initial use and torque application?

Re: Cometic gaskets
 

A legendary engine builder, Lee at Lab engine strongly recommends them.
I like Felpro, but Cometic really is the cutting edge in performance gasket technology.
Cometic provides so many more different bore sizes and thicknesses than anybody.
Whatever the cost, they are worth every cent ! BBB

Re: Cometic gaskets
 

Reusable? Or is it one use and they are out?

Anybody?

Re: Cometic gaskets
 

Cometic says yes as long as you measure them and they come up to .015 thicker than the compressed thickness. I dont know if I would, too much work if one leaks.

The key is to not let any debris get between the layers. That might be hard after using once. If I was going to reuse, I probally would apply copper coating to the gasket. A friend of mine does that every time. I just use them bare and open the package right before I install it to keep it clean.

Re: Cometic gaskets
 

I used them with lots of nitrous in a pro streeter,not one issue!

Re: Cometic gaskets
 

Several companies make multi layer gaskets including Fel Pro.

Re: Cometic gaskets
 

Where do I find the acceptable compressed thickness figure?

Re: Cometic gaskets
 

they come in different sizes

Re: Cometic gaskets
 

One good thing about cometic gaskets is that they handle detonation really well. I was running 10.2;1 compression on my engines, and the detonation actually damaged the pistons before the head gaskets.

These things are good !

Re: Cometic gaskets
 

What Cometic told me was, If the gasket is suppose to have a .040 compressed thickness, if you measure them uncompressed with a dial caliper, you need to get at least .050 to .055. I did not spend much time quizzing the guy since I had new ones and it did not matter. If this is something you want to do, give Cometic a call and hear what they have to say first hand. That call I made was over a year ago, so they may not recomend that any more. I still would not use them over.

Re: Cometic gaskets
 

One of the keys to having all the time success with Cometic head gaskets is to make sure the block and head surfaces are correctly finished , free of nicks and gouges or scratches and to make sure you use a good cleaner like alcohol or such to clean both surfaces before assembly and make sure you do not get carried away with head bolt thred sealer-lubricants that will squish into the gasket seal area when installing. Also inspect the viton(black) coating for gouges, abrasion and such because it is this coating which actually fills in the tiny voids in the surfaces when the gaskets are torqued. Proper torque in proper pattern in at least three steps is also advised. We have been using exclusively Cometic head gaskets for over three years on all our 496 engines and kits without one failure or problem. They are in my opinion definitly the best head gasket for marine use. Yes we do use them over on the dyno motors several times and checking the uncompressed height is a must when you do this.

Ray @ Raylar

Re: Cometic gaskets
 

Did we come to a consensus regarding the need to retorque after intial run in period? Always needed to do this on new conventional style fel-pros.

Re: Cometic gaskets
 

If you have properly torqued the Cometic head gaskets once , thats all they will ever need.

Ray @ Raylar

Re: Cometic gaskets
 

I've heard nothing but good things about Cometic gaskets. They are the latest technology but I think they've been around for several years but were used primarily in race bike applications. I've noticed lately that now Mr. Gasket and Fel-pro are making the MLS gaskets as well, at competitive prices.
I agree with Ray that particular attention needs to be given to the finish of the deck and heads.
The Cometics actually come with instructions which tell you that the finish needs to be like 5 ra (I think its 5). Ra is basically the smoothness of the finished surface. I not sure what method is used for this so talk to a machinist/engine builder. I recently read an article on the new Fel-Pros which indicated that the Fel- Pro gasket require less of a smooth surface because they coat the outer layers with Viton which fills in minute surface imperfections. I also noticed that the Fel-Pros are made of Stainless Steel layers. I'm not sure about the Cometics. Anyone know whether the Cometics are stainless? I have a set that I'm hoping to use in salt water so I'm thinking the stainless is the better way to go.

Re: Cometic gaskets
 

I've just checked Cometic's website and the correct finish standard is 50 ra.
Also, the gaskets layers are Stainless Steel and the outer layers are coated with a .001" layer of Viton. They are intended to be installed without any sealers.
From what I've seen and heard, it seems they're the way to go.

Re: Cometic gaskets
 

Can someone explain 50 RA in laymans terms?

Re: Cometic gaskets
 

RA is roughness average and it is exactly what is sounds like. Think of it as the machining equivalent to a sandpapers grit.

Re: Cometic gaskets
 

Thank you Ray :D