Cometic Head Gaskets $139.99

[3400-95-Modified]

They were 4 layers for a .060 set, three were stamped, two back to back, then the thick and one more stamped one... I do not know what the thicknesses were.

[chri0029]

Thanks. That is really good if they had 3 embossed layers. That means they were designed for performance. 4 would be better (that is what the LS9 has), but sometimes that is not possible due to design constraints.

Now I am just wondering now how high the stopper is (or if it has one). That would most likely be on the only layer without embossed beads (the thick center layer) between where the embossed combustion bead sits and the bore. I assume the bore opening is probably around 95 or 96 mm to work on the newest LX9's, LA1's, LG8's, etc.

[3400-95-Modified]

Bore opening would be whatever you wanted it to be, stock 3500 was 3.720 and you can go up to .060 over, I checked...

There was no question in my mind that these were made for performance or not... Cometic is a VERY reputable company... It just sucks that this first run was not biased on the right gasket and that just put their completion of the fix too far after when I needed them. Otherwise I would have definitely used them.

I don't think these had a stopper bead from what I'm reading about what one is. I do not remember seeing something like that, but I could be wrong.

[SappySE107]

.060 thick had 5 layers. Embossed, flat, embossed, flat, embossed. I don't know what a stopper is.

[chri0029]

The stopper puts pretention in the head around the bore. Think of it as a transfer of the bolt load directly to the area that needs the highest sealing - the bore. It also acts as a compression limiter so the beads are not crushed flat. That limits their spring recovery long-term. Otherwise, you will develop fatigue cracks in the beads over time which cause leaks.

That's the secret to MLS gaskets - the embossment beads act as springs. Your cylinder pressure is balanced against your bolt loads. The more cylinder pressure you have, the less your bolts hold clamp and the more your head lifts. MLS beads spring to seal that dynamic vertical lift. Old graphite and composite designs had significantly less ability to do this. All new designs are MLS for this reason.

The stopper is a flat piece of steel near the bore on the flat layer about 1 mm wide. Without it, the overall CHG design is much weaker.

[SappySE107]

The OEM 3900 and 3.6 DOHC gaskets are 3 layer and has a stopper (looks like an embossing though in an otherwise flat middle plate). The Cometic has 2 flat pieces surrounding an embossed middle.

[chri0029]

Right ... the stock 3900 and 3.6 don't have crazy boost. That's why they only have 2 embossed layers. Look at the production LS9 gasket and see what you get. Try to take a pic of the Cometic stopper area since I don't understand what you are saying.

[eckoxl]

Any updates about the gaskets?

[SappySE107]

nope

[eckoxl]

Since the ETA was 3-5 weeks, what happens after 5 weeks (next week) if the gaskets aren't done?

[SappySE107]

People will be more upset than they are now?

[robertisaar]

People will be more upset than they are now?

like late parts have discouraged the roller rocker fanatics?

[scott0999]

could we get a new ETA?

[3400-95-Modified]

I ended up going with the stock gaskets which allowed me to finish my motor, but unfortunately I inverted two retaining clips in my trans which locked the input clutch and killed it... so I'm still on jackstands... LOL Hopefully their ETA is only a week out because they are passed their 5 week max if I did my math right. How many people are waiting on these to get a project done?

[geldartb]

kinda glad i held off on these till this coming winter.