Cometic: Coated v. Uncoated

[Chezedik]

Alright, if anyone is aware, I have had serious vacuum and oil consumption issues that I have traced to AT LEAST my Cometic. It is the uncoated (non-Viton) treated with Permatex Head Gasket sealer (I guess not!). Anyway, how many of you have used the coated Cometics with good luck, without treating the block or head.

Oh BTW, before I hear about it from Cory, I know that they are good when properly installed, but I am not pulling my engine again! So I am asking those who have installed them in the same manner.

Anyone with any worthwhile input (don't just say they suck, tell me why) or people who aren't trying to belittle others (no crawling up someone's *** for what they have to say), please let me know what you think.

[extreme135]

I just put my cometic gasket on for the second time, my first build I did not use any copper spray on it just the gasket with the head,front cover and block decked, tightened the headdown with arp studs to 75LBS. after running the engine for about 30 seconds, oil started leaking out the exhaust side of the head some, but after running the engine for about 30 min. it stopped completly, my second build with the same gasket I sprayed it with copper spray and torqued the head to 80ft.lbs., did not have any leaks at all. But both times had the block, head and front timing chain cover decked and surfaced, if it is not clean level with a polished looking finish, you likely will have problems, because it is metal, I have heard of guys block sanding the head and block and getting away with, but i would not personally, what do you have it torqued down to, you might fix your problem by torqueing the head down some more.

[Chezedik]

I am torqued to 70, I may try a little more tq. Anyone else?

[480sx]

Well iv had my heads of twice already, and now that my engine is together and running iv noticed i have the same problem that Extreme had. I dont understand why the HG's dont come with that information, that you need to coat them with Copper spray or some equivalent. Mines leaking oil like a civ all over the exhaust side, not sure about the intake side because i cant see it! Basically means i have to take the heads off again(joy! im becoming a Ka pro :/).

I took time to try and resurface the block and heads myself. Took 180 grit, then 220, all the way to 500 grit. Im sure taking the block and HG to a machine shop to get them to resurface it would have gotten a more even job, but i doubt it would have made a huge difference. I just feel that without the coating the Cometic is destined to leak. I mean this thing is just pouring oil over my block...

Has anyone tried other brands of metal HG's? Im curious if its just a Cometic thing or if all metal HG's need sealer.

[Chezedik]

Actually they tell you not to, but mine did not have the viton coating. They claim that the copper will kill the viton. BTW, turns out my TQ wrench failed when putting the head on. I just checked it today, and it was 40 or less! TQ'd to 80, I will let you know how it goes.

[Florida240sx]

Wow..... You couldn't tell by feel that you were off by half?

[Chezedik]

That's why I have to assume that it just needed to be retorqued, because I should definately be able to feel that difference, right?

[sniperbill3]

You should feel the difference immediantly, the same thing happened to me when i put on a head gasket for the 2nd time after overheating the first one.

[wild_maxx]

the improper torque probably caused your leak. I was reading the instructions for my Cometic HG and it said:

1) dry installation recommended. 2) mating surfaces must be smooth 50 RA or finer

I took a few pics of mine. It does have the viton seal you are talking about. Its around the water passage and thats the only one. (click for larger image)

[nissanfanatic]

Go buy another torque wrench..

or

If its Craftsman, take it in and report the fault.

At the very least, borrow one that is in tolerance so you aren't just guessing.

[Chezedik]

I have a replacement wrench now, I got it at Advance. Theirs are lifetime warranteed, but Craftsman are only 1 year.

Also, they recommend dry installation on Viton applications. Mine is not a viton. Improper TQ definately caused my leak. We will see how it turns out.

[nissanfanatic]

I used copper spray-a-gasket on my Viton coated Cometic. I would highly recommend it. It will move if its not needed.

[eazye2000]

I used a .074" cometic on my KADE.Head and block were not decked or surfaced.Engine had 179k at rebuild.Machinist confirmed straightness on both head and block.I wire wheeled and polished both the head and block surface.I did not copper coat the cometic, nor was it coated or whatever.

I have 400 miles or so on my motor, and no leaks. I used a 5-step process when torquing down the studs to ensure consistency. I used the JGS steps and specs and added a few of my own.

I have no idea why mine is still ok at 14psi so far. Maybe it's the luck of the draw. I have no idea. But by rights, mine should be leaking from all the 'neglect' and lack of preparation on my part.

[nissanfanatic]

You must have done good prep work.

You also used a thick *** Cometic...hehe

[rotorimp]

3000 miles on the motor (cometic-decked block and surfaced head) arp studs torqued to 50ft/lbs--used copper coat non viton gasket no leaks to report.

[drEameRvaJ]

What's the difference between a cometic headgasket and a felpro?

Which is better? I'm gonna have 11MM or 10MM head studs to go with which ever headgasket I go with..

[extreme135]

A cometic HG is metal, wich is much stronger than a stock felpro HG, the cometic is reusible in most cases and will hold much much more pressure(psi) than a felpro gasket, and works very well if installed properly.

[1WheelWonder]

Since torque wrenches were mentioned, the Craftsman wrenches are only 1 year however your local Sears store or Sears service center will service/calibrate them for free, most Sears stores will have to send them off which takes a week or so.

[Chezedik]

Yeah, I said that earlier! j/k. I didn't know that they would recal for free.

I would love to tell you all how this turned out, but of course I lost spark. If it isn't one thing, it's another. I bet it is just a broken wire. I think emanage may have to come out and Mega-squirt may be in.