Athena Jug And Cometic Head Gasket

[terse]

Here is the old Cometic I had on this Athena motor. You can see where it blew "outward" and it was leaking coolant out of the mating surface. It never blew inward just outward, so it never mixed coolant with oil or coolant into the combustion chamber. The black stuff on the gasket did melt and got on the piston, and part of the gasket around the piston area snapped off and broke about 75% of the way around, and could have broken completly off and into the cylinder destroying the jug, piston and valves.

Top side: facing the valves.




Bottom side: Facing the piston.



And where the gasket broke off.



No marks were on the piston and there is no way the piston hit the gasket. The Cometic gasket is alot wider in that area then the piston is wide. I personally think the gasket was faulty, but have no real way to prove it.

[N.J.C.]

I'm sold! Pinned!

[drnez]

QUOTE (tersejr @ Jul 26 2007, 04:46 PM)

And where the gasket broke off.

[/b]

This is exactly how my cometic gaskets looked after they were blown. broke the same way, and the blow through was also very similar.

[terse]

QUOTE (drnez @ Jul 26 2007, 03:33 PM)

This is exactly how my cometic gaskets looked after they were blown. broke the same way, and the blow through was also very similar.[/b]

No kidding! Hmmm..... You got me thinking now.

[NormalZ]

QUOTE (tersejr @ Jul 26 2007, 01:46 PM)

The black stuff on the gasket did melt and got on the piston, and part of the gasket around the piston area snapped off and broke about 75% of the way around, and could have broken completly off and into the cylinder destroying the jug, piston and valves.[/b]

Terse, what's the exact bore diameter of this specific blown Cometic gasket?

[LittleMissE]

QUOTE (NormalZ @ Jul 28 2007, 01:01 AM)

Terse, what's the exact bore diameter of this specific blown Cometic gasket?[/b]

94.86mm


Also, we all just came back from a hard dune trip, and the Athena brand head gasket with coper spray did not leak, blow, spew, over heat or anything, and is holding up perfect. Yes it is in a 14.25 motor.


**this is Tersejr... forgot to log LittleMissE out first**

[nator187]

Little addition to this story. I had a 96mm Cometic gasket that I modified for my Athena. I did one layer at a time and started with the steel spacer.




Woody

[terse]

Thanks nator187.

This Z motor is still currently kicking azz with the stock Athena head gasket. No leaks, no over heating.

I have modified a Cometic head gasket for my personal Athena 480 yfz like nator did. Although I did all 3 layers together with a fine grain dremel stone. Took lots of time to not have burred edges. It has held up for 3 dune/ drag trips, but still holding my reservations on it.

[cheapracer]

Well I guess I'll throw my experience in here seeing as how I just stepped into this myself. After several years of use the compression began to drop off on my Z. Not unheard of seeing as how much ride time it got and it was time to change out the cam chain (only 2 clicks left) and clutch anyway. I pulled the head and the cylinder, I had the cylinder re-plated and I re-ringed the piston. Cylinder was completely flat, I checked with a straight edge, cylinder head was flat, also checked. Ordered up the Cometic gasket as, you guessed it, it was half as much as the Athena gasket. Put it all back together, yes I noticed the Cometic didn't line up with the cylinder cooling passages very well (the Athena wasn't perfect either) so I carefully trimmed it out so it lined up around the coolant passages and made sure there was no sharp edges or burrs on it. I used the copper spray sealant (I always do), and torqued everything down in 4 steps. I ran the engine for quite a while on Friday until the fan cycled on twice. I shut it down and let it cool completely and checked the coolant level and it was perfect. Let it sit overnight and checked in the morning (Saturday) and the level was still perfect. I fired it up again and let it run until the fan cycled on and off twice more, I let it cool completely checked and it was still fine. I then checked the oil level (perfect) and put the plastics on. We went riding on Sunday, I let the Z warm up completely before taking it out on a short ride, maybe a mile or so and it was running great but I needed to get some load on it to help break in the new rings so I headed out on a flat dirt fire road. At this point I noticed a slight buzz from the engine. Nobody else in group could hear it but I could. In neutral you couldn't hear it but in gear you could so I putted back to camp in 2nd at about 15mph according to the GPS. Total distance ridden was about 3 miles. At camp I checked the oil level.....completely full right to the top and the upper radiator hose was cold (no coolant).

After it cooled off I checked the radiator and it was down about 2 inches. I pulled the oil pressure test port screw out and bumped the starter and got a small sample of the oil in the engine and it looked like it had milk mixed in. The only difference between the last build and this one was the Cometic gasket. If you have a stock over bored cylinder use the Cometic, if you have an Athena cylinder spend the extra cash and get the Athena gasket. Either that or plan on doing it twice.

[87 s10]

I was reading a couple of pages back where someone said that was the stupid to put silcone around headgaskets well it's not I do the same thing on my mustang it works I spray alot of nitrous on my car and I kept blowing headgaskets a guy that builds race motors at the local machine shop told me to put a bead of silcone around where the piston comes up on gasket in a circle than put your head on top with arp head studs than when the head raises up the silcone stretches to keep gasket from busting