Head gasket choice. MLS or Composition
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Head gasket choice. MLS or Composition

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    Default Head gasket choice. MLS or Composition

    540CI, 8.0:1 compression, max 8-9psi of boost, 850-900hp pump gas hyd roller 6000rpm max. Engines are in a heavy twin engine 38 Cigarette. We removed heads last night, as the valve leakage was excessive. Heads are in shop for rebuild. Head gaskets were showing signs of possibly a little leakage between cylinders. Previous engine assembler used a lot of copper rtv on the decks/heads when assembling with cometic MLS. Anyhow, the pistons are out of the hole about .005. I suggested getting Felpro MLS .053 thick as replacements. I like the coating on the felpros over the cometics personally. Both block and heads have proper RA finish. Cylinder head guy suggested standard composition type gaskets, but, I only see felpro has one thickness with the 1047 or 10748 stainless fire rings, and that's .039. I think that might be a little too tight for my liking with the pistons where they are. Any thoughts? He would like to not have these heads back off for a while.

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    Great question Joe!

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    Quote Originally Posted by Mild Thunder View Post
    540CI, 8.0:1 compression, max 8-9psi of boost, 850-900hp pump gas hyd roller 6000rpm max. Engines are in a heavy twin engine 38 Cigarette. We removed heads last night, as the valve leakage was excessive. Heads are in shop for rebuild. Head gaskets were showing signs of possibly a little leakage between cylinders. Previous engine assembler used a lot of copper rtv on the decks/heads when assembling with cometic MLS. Anyhow, the pistons are out of the hole about .005. I suggested getting Felpro MLS .053 thick as replacements. I like the coating on the felpros over the cometics personally. Both block and heads have proper RA finish. Cylinder head guy suggested standard composition type gaskets, but, I only see felpro has one thickness with the 1047 or 10748 stainless fire rings, and that's .039. I think that might be a little too tight for my liking with the pistons where they are. Any thoughts? He would like to not have these heads back off for a while.
    MLS require a good finish, but they also need an absolute flat surface. There is a difference. Head/block surfacers that use a rotary broach typically have the head tipped some to avoid back-dragging the cutter, but in turn, this creates a slight scallop to the cut. Composite gaskets have the ability to compress unevenly if this is the case, MLS gaskets cant. An almost sure sign of this is leaking between cylinders. The other thing is, I would not recommend using any sealer like RTV or silicone with MLS gaskets. If you think you need some extra sealing, I'd use a spray sealer like Copper Coat that you can apply evenly but on fresh surfaces with new gaskets, it shouldn't be necessary. It sounds like you're pretty much dictated to an MLS gasket with your thickness issue. Looks like the 1017-2 is .051" but only fits Mk4 blocks. Personally, I would recommend the MLS just because of the severe application.
    Last edited by scott foxwell; 01-15-2014 at 07:11 AM.
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    Senior Member ICDEDPPL's Avatar
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    Heres some pics:





    This doesnt seem like a good valve job to me:

    http://33outlaw.zenfolio.com/img/s5/...307208-215.mp4

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    Quote Originally Posted by steelcomp View Post
    MLS require a good finish, but they also need an absolute flat surface. There is a difference. Head/block surfacers that use a rotary broach typically have the head tipped some to avoid back-dragging the cutter, but in turn, this creates a slight scallop to the cut. Composite gaskets have the ability to compress unevenly if this is the case, MLS gaskets cant. An almost sure sign of this is leaking between cylinders. The other thing is, I would not recommend using any sealer like RTV or silicone with MLS gaskets. If you think you need some extra sealing, I'd use a spray sealer like Copper Coat that you can apply evenly but on fresh surfaces with new gaskets, it shouldn't be necessary. It sounds like you're pretty much dictated to an MLS gasket with your thickness issue. Looks like the 1017-2 is .051" but only fits Mk4 blocks. Personally, I would recommend the MLS just because of the severe application.
    I did see the 1017-2 gasket, but its listed as a non stainless ring gasket. the 1047 and 10748 are, but only avail in ..039 I believe. Scott, I have used the FelPro MLS gaskets, with good luck. I really like the black sticky coating on them. Actually, one of my engines has Cometic gaskets with copper coat, the other Fel PRO MLS that went on dry out of the package. No issues with either. Just wish felpro offered more sizes like cometic does. Is it fair to say that you agree with going with the thicker .053 gasket in this application? Thanks!!

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    Quote Originally Posted by Mild Thunder View Post
    I did see the 1017-2 gasket, but its listed as a non stainless ring gasket. the 1047 and 10748 are, but only avail in ..039 I believe. Scott, I have used the FelPro MLS gaskets, with good luck. I really like the black sticky coating on them. Actually, one of my engines has Cometic gaskets with copper coat, the other Fel PRO MLS that went on dry out of the package. No issues with either. Just wish felpro offered more sizes like cometic does. Is it fair to say that you agree with going with the thicker .053 gasket in this application? Thanks!!
    The black sticky stuff on the Felpro MLS is no more. Last couple sets of Felpro MLS I bought had a coating similar to the Cometic,

    Leakage between cylinders with the MLS gaskets can be due to using sealer. Even copper coat. If you are going to coat them, do it every where except between the cylinders. The other cause of leakage between cylinders is what Steel said. If the machinist tilts the head on the surface just a little too much to prevent back cutting/drag, then it will create concave/dip down the center of the head. Right where you need it the least.
    The MLS gaskets are great and they take a hell of lot of abuse, but the harder you lean on them, the better everything has to be right, or they are no better than anything else.

    IMO the Felpro composite can take anything pump gas can handle so long as you don't get it in detonation. I used them with all the boost I could produce on 110 race gas and never hurt one. You could never produce enough cylinder pressure to blow one on pump. But detonate it, and they're toast. But like you said, they don't make a thicker gasket with a SS core.

    I had the same issue with thickness and used SCE ICS Titans and I love them. Just an option.

    BTW, what block is that in the picture? At first glance it looks like a Gen 5, If it is, the gasket appears to be the wrong gasket. If its an early MK IV bowtie, never mind.



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    Last edited by gn7; 01-15-2014 at 09:21 AM.

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    Quote Originally Posted by gn7 View Post
    The black sticky stuff on the Felpro MLS is no more. Last couple sets of Felpro MLS I bought had a coating similar to the Cometic,

    Leakage between cylinders with the MLS gaskets can be due to using sealer. Even copper coat. If you are going to coat them, do it every where except between the cylinders. The other cause of leakage between cylinders is what Steel said. If the machinist tilts the head on the surface just a little too much to prevent back cutting/drag, then it will create concave/dip down the center of the head. Right where you need it the least.
    The MLS gaskets are great and they take a hell of lot of abuse, but the harder you lean on them, the better everything has to be right, or they are no better than anything else.

    IMO the Felpro composite can take anything pump gas can handle so long as you don't get it in detonation. I used them with all the boost I could produce on 110 race gas and never hurt one. You could never produce enough cylinder pressure to blow one on pump. But detonate it, and they're toast. But like you said, they don't make a thicker gasket with a SS core.

    I had the same issue with thickness and used SCE ICS Titans and I love them. Just an option.

    BTW, what block is that in the picture? At first glance it looks like a Gen 5, If it is, the gasket appears to be the wrong gasket. If its an early MK IV bowtie, never mind.
    Thanks for the Reply GN. Yes, they are mark IV bowtie blocks. I have seen the standard Felpro 10748 Marine gasket withstand 12lbs of boost on a procharged 522 no problem. I just wished they made it in a thicker gasket with a stainless core. I hate that most of the machine shops are always shooting for 0 deck. Seems like every engine I come across lately has been 0 decked, or even further. That sucks about the felpro coating, I liked that. Who knows what they did here on the install with the cometics,. I was always told cleanliness is imperative when dealing with the cometic during install, as even a tiny piece of dirt between the layers can be detrimental to sealing. I think, with proper RA, flat surfaces, everything clean, and a proper head torqueing procedure, everything would be ok whether cometic or Felpro. I know a bunch of marine builders claim they have best results with the cometics going on dry, and absolutely no silicone/rtv used.

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    These engines have Dart iron 345 heads, with ARP headbolts. On my engines, I have ARP head studs. Probably way overkill for what I am doing as far as boost, and not needed, but they make me feel warm and fuzzy. Any thoughts on going to a stud kit on these engines in question, or waste of money?

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    Quote Originally Posted by Mild Thunder View Post
    Thanks for the Reply GN. Yes, they are mark IV bowtie blocks. I have seen the standard Felpro 10748 Marine gasket withstand 12lbs of boost on a procharged 522 no problem. I just wished they made it in a thicker gasket with a stainless core. I hate that most of the machine shops are always shooting for 0 deck. Seems like every engine I come across lately has been 0 decked, or even further. That sucks about the felpro coating, I liked that. Who knows what they did here on the install with the cometics,. I was always told cleanliness is imperative when dealing with the cometic during install, as even a tiny piece of dirt between the layers can be detrimental to sealing. I think, with proper RA, flat surfaces, everything clean, and a proper head torqueing procedure, everything would be ok whether cometic or Felpro. I know a bunch of marine builders claim they have best results with the cometics going on dry, and absolutely no silicone/rtv used.
    I've used Cometics pretty much exclusively for the last 9 years and knock on wood, never had an issue. Zero deck gives you a lot more latitude with head gasket choice. We have Detroit graphite/composite gaskets that are .039", less than half the cost of a MLS and will take anything you can throw at them. Max bore available is 4.50 (Gasket is 4.53) for both Mk4 and Gen blocks.
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