LTx engines using Cometic MLS headgaskets
Thread Starter
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
LTx engines using Cometic MLS headgaskets
Has anyone here used the Cometic MLS style headgaskets on a LTx engine and experienced oil seepage at or near the number 7 or 8 cylinders. I have a problem with oil seeping out near the inside head bolt just below the 7 and 8 exhaust ports. Oil is not coming from above at the valve covers nor is it coming from the intake china wall area.
Le Mans Master
Joined: Oct 2004
Posts: 5,841
Likes: 19
From: CLT, North Carolina
The Cometic MLS gasket is a very good gasket. We saw a marked reduction in cylinder wall distortion when we went to it but the block must be honed with them under the honing plates or you could actually have increased distortion if honed with another style gasket such as a composition. Anyway, I am digressing; to address your question, it is highly likely the oil leak is originating in the corners where the head intake flange intersects the block deck and china rail and could be following the edge of the gasket between the head and deck and running down where you see it. Clamp load decreases the further away you get from any head bolt and the narrow portion of the MLS gasket up towards the china rail is notorious for leaks because of insufficient clamp load. We usually apply a thin film of silicone between the layers about an inch down from the ends in that region. I understand Cometic is now rolling a bead in that area to address this problem. All our gaskets have this correction however Cometic makes our gaskets to our specifications so you might have to ask for the bead.
Regards, Greg
Regards, Greg
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
Originally Posted by tjwong
Has anyone here used the Cometic MLS style headgaskets on a LTx engine and experienced oil seepage at or near the number 7 or 8 cylinders. I have a problem with oil seeping out near the inside head bolt just below the 7 and 8 exhaust ports. Oil is not coming from above at the valve covers nor is it coming from the intake china wall area.
Le Mans Master
Joined: Jul 2000
Posts: 5,012
Likes: 5
From: OKC OK
You might wanna contact Ai. I think they recommend/use them. I've heard/read that getting a good seal is sometimes difficult w/ them...it had something to do w/ the proper head & block surface texture.
Thread Starter
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Originally Posted by Baldturbofreak
Tj, I had a problem with mine with the AFR heads hitting the Rivits that hold the gasket together. The solution was pulling the heads back off, cutting the rivets off, reinstall. All good
and I double checked the china wall, head and intake meeting points. I assembled the engine on the stand and made double sure that that area was well sealed. There is no sign of oil from that area and none from the valve cover seal. I am very perplexed, disgusted and totally frustrated. This car is my nemesis, it just won't go away It runs great, looks great but the damn thing sprung a leak in a place I would have never thought it would leak. It happens to leak just at those rivets, I spoke with Cometic, and Mr Gasket. Cometic made these for Mr. Gasket, they told me that they had three other complaints so they are going to have Cometic redesign the gasket for them. The new version will have a high temperature silicone coating that is 1mil thick, whereas the present gasket has a elastomer coating .001 thick. They are sending me a new set of gaskets, but I still have to tear the engine down which I don't want to do. The thing looks so damn good now and its spotless.
Thread Starter
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Originally Posted by Baldturbofreak
Tj, I had a problem with mine with the AFR heads hitting the Rivits that hold the gasket together. The solution was pulling the heads back off, cutting the rivets off, reinstall. All good
Originally Posted by LT4POWR
You might wanna contact Ai. I think they recommend/use them. I've heard/read that getting a good seal is sometimes difficult w/ them...it had something to do w/ the proper head & block surface texture.
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
I discovered the problem before ever firing the motor, But with the drysump and 20" of case vacuum I doubt it would have leaked out. IN maybe but not out.
But just to make myself feel better I hit mine with a coat of permatex High Tack. Basically I treated them like a pair of copper gaskets. They want like a freakin 20 RA finish on the deck to work as delivered.
Damn LT1's with boost have the worst trouble with case pressure induced oil leaks. EVERY ONE!
I feel for ya TJ. I sure know what it's like to have a wholly uncoooperative car kick your **** around the shop.
But just to make myself feel better I hit mine with a coat of permatex High Tack. Basically I treated them like a pair of copper gaskets. They want like a freakin 20 RA finish on the deck to work as delivered.
Damn LT1's with boost have the worst trouble with case pressure induced oil leaks. EVERY ONE!
I feel for ya TJ. I sure know what it's like to have a wholly uncoooperative car kick your **** around the shop.
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Drifting
Joined: Aug 2001
Posts: 1,500
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From: Holliston MA
Cruise-In VII Veteran
I cut the rivets off mine on a L98 style, seperated the 3 pieces, spray coppered each, both sides, 3 coats, and installed them. Also ran a finger smear of Permatex #2 along the head to block parting line in the lifter gallery. No leaks so far. I've heard other similar complaints. You can reuse those gaskets. I ended up having to pull the heads back off to install a set of raised tie bar solid lifters.
Thread Starter
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Originally Posted by SloRvette
I cut the rivets off mine on a L98 style, seperated the 3 pieces, spray coppered each, both sides, 3 coats, and installed them. Also ran a finger smear of Permatex #2 along the head to block parting line in the lifter gallery. No leaks so far. I've heard other similar complaints. You can reuse those gaskets. I ended up having to pull the heads back off to install a set of raised tie bar solid lifters.