Thread:

MLS Head gaskets

Fel-Pro 1075, .041 compressed thickness.

If a MLS gasket is supposed to be a specified thickness when installed (compressed), can someone please explain why these gaskets (30 hrs run time), are measuring less then that after removal.



The most likely spot for a leak, is less then the compressed height by .005 - .006. Both the head and block are showing signs of leaking. Block was square decked .015, heads were milled .020, and both still check perfect.

Originally Posted by 28Eliminator

Fel-Pro 1075, .041 compressed thickness.

If a MLS gasket is supposed to be a specified thickness when installed (compressed), can someone please explain why these gaskets (30 hrs run time), are measuring less then that after removal.



The most likely spot for a leak, is less then the compressed height by .005 - .006. Both the head and block are showing signs of leaking. Block was square decked .015, heads were milled .020, and both still check perfect.

Are they thin just between the cylinders? What's the condition of the gasket?
I'd say you have a problem there. There should be no reason they'd be that way, especially with as mild a build as yours.

Originally Posted by coolerman

The "spring" to them is what makes the MLS gaskets work; ie: the "spring" is what makes it seal when the head slightly lifts and moves around. On a high output motor where there is a lot of heat, they will loose their "spring" to them. This is especially true on a 4.6 bore where the motor cannot dissipate the heat between the chambers due to the small amount of meat/webbing between the cylinders.

What are some more specs on your motor? Bore? HP?

"Spring"? Do you mean the embossing?

Originally Posted by steelcomp

Are they thin just between the cylinders? What's the condition of the gasket?
I'd say you have a problem there. There should be no reason they'd be that way, especially with as mild a build as yours.

Yes, only between the cylinders, were they thinner then the .041 supposed compressed thickness. They look fine, and appear to have sealed everywhere else.

This makes absolutely no sense to me. At worse, they should be no less then the .041, under any circumstances...

Got a call back from Fel-Pro yesterday afternoon. He told that the reason the Gasket was collapsed below the "Compressed height" between cyl's, was because I had an air pocket in the cooling system causing the head to expand and "squeeze" the gasket out of shape

Originally Posted by 28Eliminator

Got a call back from Fel-Pro yesterday afternoon. He told that the reason the Gasket was collapsed below the "Compressed height" between cyl's, was because I had an air pocket in the cooling system causing the head to expand and "squeeze" the gasket out of shape

He is not totally crazy. There is no water right where you measured it between bores on a siamesed block. Detonation will do the same thing to a head gasket. But your engine didn't seem to show signs of detonation in other cylinders.
But heat will do that to a gasket.

Its not so much that the base gasket is thinner, as much as the embossing is smashed flatter, annealed, and did come back.

Originally Posted by gn7

He is not totally crazy. There is no water right where you measured it between bores on a siamesed block. Detonation will do the same thing to a head gasket. But your engine didn't seem to show signs of detonation in other cylinders.
But heat will do that to a gasket.

Its not so much that the base gasket is thinner, as much as the embossing is smashed flatter, annealed, and did come back.

I can only assume that an Aluminum head motor would be even worse. Are the Cometic's any more resilient to the crushing? This is really disappointing. Cometic makes some very thick MLS Head Gaskets, and I would think there has to be some expandability/resiliency for expansion and contraction, especially at the extreme thickness's of some of them..

Maybe I should just a $29 NAPA head gasket and call it good

Originally Posted by 28Eliminator

I can only assume that an Aluminum head motor would be even worse. Are the Cometic's any more resilient to the crushing? This is really disappointing. Cometic makes some very thick MLS Head Gaskets, and I would think there has to be some expandability/resiliency for expansion and contraction, especially at the extreme thickness's of some of them..

Maybe I should just a $29 NAPA head gasket and call it good

Thats the job of the embossing.

Personally, for less than blown applications, I still like the Fel Pro performance line over the cometic/Fel Pro MLS. They are easier on the aluminum heads, and I have ran 12 lbs of boost on 9 to 1 compression without failure. They are way more forgiving to block and head maching, and they are cheaper. I don't use Cometic/FelPro MLS unless I have to.

Originally Posted by WETTE VETTE

Is the black coating on the gasket still there between the cylinders where the gasket is measuring thin?

Not really.. most of it is gone off the gasket, but some is still there, and appears to have been transferred to the Head and Block for the most part..