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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.

Motor 164.jpg Motor 167.jpg Motor 165.jpg Motor 166.jpg Motor 168.jpg

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.
 

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I didnt put caliper to mine but I seen some of the same signs on my block between the a few cylinders.
 

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I didnt put caliper to mine but I seen some of the same signs on my block between the a few cylinders.
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?
 

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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.

View attachment 148791 View attachment 148792 View attachment 148793 View attachment 148794 View attachment 148795

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.
 

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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?
 

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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...
 

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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 :rolleyes:
 

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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 :rolleyes:
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.



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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 :D
 

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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 :D
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.



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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..
 

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so gn7 do you think or feel it would be safe to run a felpro performance line head gasket in a bbc with 13.5 to 1? and if so, what about nitrous on top of it? I personally went with the mls because of the high comp and nitrous, I thought of it as insurance, but I might need to take a head off and am not sure if it's a problem with the mls gasket or not. Needless to say they are pricey lil fockers! and if I could be safe with the performance line, then all the better.
 

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so gn7 do you think or feel it would be safe to run a felpro performance line head gasket in a bbc with 13.5 to 1? and if so, what about nitrous on top of it? I personally went with the mls because of the high comp and nitrous, I thought of it as insurance, but I might need to take a head off and am not sure if it's a problem with the mls gasket or not. Needless to say they are pricey lil fockers! and if I could be safe with the performance line, then all the better.
13 to 1 is fine. NOS? You just stepped over the line. I would go with the MLS. I am all in favor of the composite performance line. I think they are much easier on aluminum heads, and they are cheaper. But in you case, I would go for the extra insurance.



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