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Thread: Cometic MLS head gasket fitting method

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    Cometic MLS head gasket fitting method

    Hopefully someone can help with the process of fitting an MLS head gasket - I'm not usually a fan of them as feedback I've had about them is they are difficult to get a decent seal - but the engine needs one of these due to bore size.

    Is the recommended method (new gasket, not used) to use oil on the faces, Hylomar blue, or dry fitting?

    The engine already has a Cometic MLS on it, I'm just replacing as the engine is coming to pieces and as it hasn't had any issues I'm confident the head/block has the correct RA finish.

    Are there any other tips or tricks?

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    Re: Cometic MLS head gasket fitting method

    i fit they dry and have never had any issues, but that has always been with freshly skimmed block and head. it might be more critical if the gasket is reused, personally i dont reuse them id rather pay for a new gasket than risk a failure, i just dont see how they can be as good a second time round.

    ondy says use blue hylomar to avoid weepage of the waterways. which is probably good advise, i dont think he does anything simply for the sake of it. hylomar can be bought in aerosol form which is good for getting a thin light application.

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    Re: Cometic MLS head gasket fitting method

    i've fit them dry but some of the american forums use copper gasket spray. apparently they can be re-used. time will tell as i have re used mine for the first time although the car did not actually run and cometic say this should be no problem

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    Re: Cometic MLS head gasket fitting method

    I was advised by a well reputed competition engine builder to use a a thin coating of Welseal on a MLS gasket.

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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by Graham View Post
    i fit they dry and have never had any issues, but that has always been with freshly skimmed block and head. it might be more critical if the gasket is reused, personally i dont reuse them id rather pay for a new gasket than risk a failure, i just dont see how they can be as good a second time round.

    ondy says use blue hylomar to avoid weepage of the waterways. which is probably good advise, i dont think he does anything simply for the sake of it. hylomar can be bought in aerosol form which is good for getting a thin light application.
    Nice one, thank you Graham. And you're right : Onyd is very on the ball (as you are too!)

    Quote Originally Posted by fatboy slim View Post
    i've fit them dry but some of the american forums use copper gasket spray. apparently they can be re-used. time will tell as i have re used mine for the first time although the car did not actually run and cometic say this should be no problem
    Something to think about for the future, thank you.

    Quote Originally Posted by Forest_rallying View Post
    I was advised by a well reputed competition engine builder to use a a thin coating of Welseal on a MLS gasket.
    That's great, thanks - do you mean a thin coating all over, or just around water and oil ways? Just wondering about how it interacts with fire rings?

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    Re: Cometic MLS head gasket fitting method

    although it seems wrong, i dont think all over would hurt ( as long as its very thin) almost all composite gaskets actually have a sprayed on coating of something sealant like

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    Re: Cometic MLS head gasket fitting method

    Ive always fitted them dry. As said above on freshly skimmed head and block.
    I have reused one on a pinto once. I had no time to re-order one and car was due out the following day rallying.
    I covered both sides with a thin coating of copper grease that came in a aerosol tin. I have to say that engine lasted well over a year, before it broke a spring and droped a valve.

    Personally i would always fit a new gasket but if time is against me again in future, the method i mentioned worked for me and i would do it again.

    Jonny

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    Re: Cometic MLS head gasket fitting method

    I never had problems dry on Honda's which are almost polish skimmed. The first one I fitted to a Pinto was fresh shimmed but more coarse and little leak of water. I was already using Hylomar on Jaguar single metal layer gaskets for the same reason. Used Hylomar and bingo, no more leak. I have reused lots of them, take them apart, clean them with Thinners and use Hylomar between every layer.

    Almost 100% sure Wellseal will do the same for a Pinto but I would not give it a try on a Jaguar. You need a thicker layer and stronger. The reason you best use an extra sealer is only because most older blocks are not fine (re) grind. The Viton layer is really thin and can not "close" the coarse lines. The Hylomar can and will. Jaguars are an other story, you can grind until the are spot on because there will be no head left to grind. You really need to close "gaps". The Hylomar did it for me all the time. BTW, I no longer use single metal on Jaguar's, also Cometic and never ever had a single issue since then.

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    Re: Cometic MLS head gasket fitting method

    Thanks for the responses everybody.

    I've heard a couple of racers (racers who are engineers and who build their own engines) struggling to get the Cometic MLS to seal on a Lotus Twincam due to the cylinder heads inherent flexibility. I'm not rebuilding a twincam so it's not relevant to my initial question but it might open up some more discussion about this subject and whether anyone else has any issues.

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    Re: Cometic MLS head gasket fitting method

    for me, i like the fact a mls cant have its fire ring blown out, but also dislike the fact the things have no give in them, which is why on pintos i either use ARP studs and a conventional gasket, or MLS and std bolts

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    Re: Cometic MLS head gasket fitting method

    interesting topic.
    and we are talking about cast iron block and cast iron heads.
    for my knowledge mls are better when used on a cast iron block and alloy head.
    what do you think?

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    Re: Cometic MLS head gasket fitting method

    I've used MLS in any combination and always sealed as it should (with Hylomar). Also fitted and MLS and ARP (most of the time because I always use ARP if I can (not standard blocks). Possible it can "give" less but i thing you would be surprised how much flex there still is. You can never get the relief complete out of it when you torque the head. So this is the flex still in and maybe we don't need flex??

    At least, I've never had any problems with these gaskets and currently to me the best gaskets for Mini's, Jaguars, MG, Triumph etc.. which sometimes have to be sealed with minimum metal between 2 cylinders.

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    Re: Cometic MLS head gasket fitting method

    Can not believe it would give an issues in a Lotus or any other combination. Unless you do it wrong or don't use sealer where needed (and did it wrong). Nor do I believe you need an iron block and alloy head. In USA the use them in any kind of V8 combination.

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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by onyd View Post
    Can not believe it would give an issues in a Lotus or any other combination. Unless you do it wrong or don't use sealer where needed (and did it wrong). Nor do I believe you need an iron block and alloy head. In USA the use them in any kind of V8 combination.
    Lotus had problems with the cylinder head during early testing and couldn't get the gaskets to seal. I believe they had to change which casting foundry they used to get a better made head. It still leaked and then the cylinder head gasket was changed to a copper faced gasket to solve the issue so I think the issue is to do with the head in that case.

    It would be interesting to hear from people who have a Lotus T/C with a Cometic head gasket and relay their experiences.

    I'll be using the Cometic with an aluminium block and head.

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    Re: Cometic MLS head gasket fitting method

    Until date, none of the engine builders I know was able to seal a Jaguar with a Cometic gasket. I'm talking about Jaguars with fairly damaged water channels. Time after time I've saved them with my tube of Hylomar (and the knowledge).

    Unless the the Lotus casting is leaking water (not the surface against the engine) I would be surprised I would not be able to seal it.

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    Re: Cometic MLS head gasket fitting method

    A good friend has a BDA head with some corrosion damage around the water openings. They do not extend into the area around the combustion chamber. In looking at it yesterday, we decided that skimming the head would not be the best idea, because this head is going on a street engine. It had been skimmed before and additional skimming would raise the compression ratio out of the range of available pump fuel.

    I have repaired aluminum casting with Devcon F with good results. Anyone have an opinion on using this product to fill the corroded areas? The head would be returned to flatness using a lapping plate.
    Last edited by greengoredstop; 20-05-2017 at 02:58.

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    Re: Cometic MLS head gasket fitting method

    If I remember correctly Devcon F can be used up until 120 degrees Celcius or there-abouts.
    Would think that's not high enough.
    Some time ago I had a BDA head here from an engine on which 2 types of coolant were mixed with alot of corrosion as a result.
    A friend specialices in alloy welding and he repaired the head.
    See photos of before and after.



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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by greengoredstop View Post
    A good friend has a BDA head with some corrosion damage around the water openings. They do not extend into the area around the combustion chamber. In looking at it yesterday, we decided that skimming the head would not be the best idea, because this head is going on a street engine. It had been skimmed before and additional skimming would raise the compression ratio out of the range of available pump fuel.

    I have repaired aluminum casting with Devcon F with good results. Anyone have an opinion on using this product to fill the corroded areas? The head would be returned to flatness using a lapping plate.

    There you go this is good gear may be of some use for you ,


    http://www.belzona.co.uk/en/applications/engines.aspx

    Belzona 1111 (Super Metal),

    Belzona 1511 (Super HT-Metal)

    Cheers

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    Re: Cometic MLS head gasket fitting method


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    Re: Cometic MLS head gasket fitting method

    Thanks guys, I will pass this along.

    Rob

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    Re: Cometic MLS head gasket fitting method

    Devcon Temp range
    120 F wet. 250 F Dry
    Please confirm if this would this be suitable?
    Attached Files Attached Files

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    Re: Cometic MLS head gasket fitting method

    Used Belzona 1111 for filling ports many times, excellent stuff!

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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by James Jordan View Post
    Devcon Temp range
    120 F wet. 250 F Dry
    Please confirm if this would this be suitable?
    120 F wet is 51.6 C my thermostat opens at 82 C and temps can go above 100 C

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    Re: Cometic MLS head gasket fitting method

    You should never use sealant on a high pressure machined gasket face, your actually creating a leak path by doing that. Re. the cylinder head, Belzona is a better product, ive seen it used in the offshore industry on pitted steel pipework flange faces for very high temps and pressures up to around 120bar.
    Last edited by Erikmex; 27-05-2017 at 14:08.

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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by Erikmex View Post
    You should never use sealant on a high pressure machined gasket face, your actually creating a leak path by doing that. Re. the cylinder head, Belzona is a better product, ive seen it used in the offshore industry on pitted steel pipework flange faces for very high temps and pressures up to around 120bar.

    All depend about the situation and what "sealer" you are using. In case of the heavy damaged BDA as in the pictures above, Hylomar or Wellseal will not help, in case of my Jaguar, Pinto with not mirror grind surfaces, it's the only way to get the job done.

    Every modern gasket has a kind of sealer on as standard. The steel once's are using a thin layer of Viton. Usual OK for very fine grind surfaces. The extra sealant, if needed, should be very very thin as well and only get into the smallest gaps (if I may call them gaps). The gasket must be squeezed between the head and block, not floating on sealer.

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    Re: Cometic MLS head gasket fitting method

    A surface finish should always be such to suit the gasket material, only rough cast parts such as alloy thermostat housings etc should need a sealant......im sure it works tho.

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    Re: Cometic MLS head gasket fitting method

    I do understand what you mean and will be so in a perfect world. But in my world, it often does not. If you try to skim a Jaguar head until it is mirror finish as needed for the Cometic you ignition plug will be touching the piston, no metal will be left, they are far to porous.

    In case of the Pinto, dismantle the engine and skim, mirror skim the block. A lot of work which can be left by using the right sealer.

    Believe me, it is working perfect with Hylomar Universal blue and I guess Wellseal can do the job also. Please note it is NOT the fire ring we are trying to seal, only the water channels to the outside of the engine. Fire ring is build up so it get's a lot of torque pressure from the bolts and will seldom (never) leak. But I did found out in complete other setup's (Beetle engine) the Hylomar does help sealing the firing.

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    Re: Cometic MLS head gasket fitting method

    A mirror finish (approx 3microns) is never what you need to make a head gasket seal, blue hylomar will never help seal a fire ring either, its temp range is only to 250degC, way below the temp transfer you'll see from combustion through a fire ring.

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    Re: Cometic MLS head gasket fitting method

    We are not talking about using hylomar or anything else to seal a gasket fire ring. I was advised by a reputable engine builder that has built DFV's to BDA's and everything in between to use a thin smear of Wellseal on the MLS gasket to prevent seepage of coolant between the head and block faces, otherwise there's a chance of water dribbling down the side of the engine block.

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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by Forest_rallying View Post
    We are not talking about using hylomar or anything else to seal a gasket fire ring. I was advised by a reputable engine builder that has built DFV's to BDA's and everything in between to use a thin smear of Wellseal on the MLS gasket to prevent seepage of coolant between the head and block faces, otherwise there's a chance of water dribbling down the side of the engine block.
    I was just reading the comment above ''But I did found out in complete other setup's (Beetle engine) the Hylomar does help sealing the firing''. Ive used MLS gaskets lots of times and never used a sealant, i dont really see the point in machining a gasket surface true only to make untrue by using a sealant, plus id never like to run the risk of getting sealant into an oil gallery.

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    Re: Cometic MLS head gasket fitting method

    It's not because Hylomar claims 250 the product will melt direct over 250. And the place where the Hylomar is fitted in between is not 250 but more like 100 (engine water temp + a few ). Only the very last part of the Cometic is in the combustion chamber, and only a few hundreds of a millimeter Hylomar is making contact. The rest is flat between the cylinders and the head.

    It will help sealing the fire ring but it's mainly to prevent water leaks. I've done the same many times in Triumph TR4. Even now one TR4 is waiting to be tested but is setup as I was asked for by the customer.

    I use Loctite 5699 for fitting exhaust systems. It's is rated for 90 water, not red hot turbo's but it did survive a full race reason in between the tubular exhaust manifold and a GT35 on one of my Honda's.

    In Beetle engine you can use it as an extra sealer. Once the cylinders are lapped into the cylinder head you got approx 4 - 5mm "wall" where it meet the cylinder head. You put a little Hylomar (universal blue) on top and fit the head. Only little, the Hylomar will be pushed out and a very nice small ring will be formed on the inside of the of the cylinder head / cylinder. Because the pressure is highest where the four studs are the rest of the head tend to lift a little (I'm talking about VERY little !!!) just enough it can make a mini mini leak after some time and of course will be bigger and bigger once gasses can pass. The gasses will try to push the Hylomar "ring" into the leak but it can't because the Hylomar is to tick. Thanks to the fact it stay's some kind of elastic it seals the head. If you would use Loctite is would be bridle and gasses will pass.

    You don't have to believe it, can even ignore reading this info but if you do have a Beetle aircooled engine, take my advice. It does help if done correct and if you only put little on it, clean all very well with cleaning thinner it can't go wrong.
    Last edited by onyd; 29-05-2017 at 14:05.

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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by onyd View Post
    I do understand what you mean and will be so in a perfect world. But in my world, it often does not. If you try to skim a Jaguar head until it is mirror finish as needed for the Cometic you ignition plug will be touching the piston, no metal will be left, they are far to porous.

    In case of the Pinto, dismantle the engine and skim, mirror skim the block. A lot of work which can be left by using the right sealer.

    Believe me, it is working perfect with Hylomar Universal blue and I guess Wellseal can do the job also. Please note it is NOT the fire ring we are trying to seal, only the water channels to the outside of the engine. Fire ring is build up so it get's a lot of torque pressure from the bolts and will seldom (never) leak. But I did found out in complete other setup's (Beetle engine) the Hylomar does help sealing the firing.

    I have had a block coated a few years ago cylinder liner water jacket space never leaked again!!!!!!!!!! & its very reasonable on your pocket aswell

    There you go this may be of use for you in the future, for your Jaguar

    http://www.surfacetechnology.co.uk/c...aseal-pc50466/

    A Lot of the Pre-War guys use this process on Cylinder blocks & cylinders heads with 100 % results
    Even the UK Motorsport Triangle use these people says it all really .

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    Re: Cometic MLS head gasket fitting method


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    Re: Cometic MLS head gasket fitting method

    For sealing cylinder in a block I use Loctite 5699 (also for sealing block, gearbox...), for head gaskets Hylomar.

    The company in the link seems to be in business with this well trusted sealer for approx 25 years and I do believe it will do the same as Hylomar. Hylomar was original invented by RR for there first turbine engine so in business for at least double the time.

    I always stick with my well and trusted ways unless I do have a problem. It means, Hylomar, Loctite 5699, NGK plugs, Castrol oil ..........

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    Re: Cometic MLS head gasket fitting method

    http://www.surfacetechnology.co.uk/c...tion-services/



    Checkout the above link as I added the wrong one in the fistplace
    Internal Impregnation sealing for porous heads, blocks , pumps & castings
    Last edited by Yanmarman; 29-05-2017 at 17:37.

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    Re: Cometic MLS head gasket fitting method

    I,ve been fitting cometic mls head gaskets dry for some time on prexflow race engines and my twincam race engine. No problems at all. Until a few weeks back.

    I was building up a twink,I always water test the TC engine before timing the cams up and fitting the sump,water started leaking down the oilway which feeds the head/cams.
    I pressured the system 10lbs approx. and water was seeping out the gasket along the side of the block.
    I removed the head thinking I'd got some crap between the surfaces.When I removed the gasket it was wet all over indicating that the gasket was not sealing round the waterway holes. Hmmmm.
    The thing that I noticed was, on the twink head the oil passage is offset and is linked with a small well .When studying the gasket, which are designed for crossflows, the oval bolt/oil hole has a raised lip to seal oil pressure. This lip does not correspond with the well in the head,hence the water was tracking from between the layers of the gasket to the oil hole.
    I've recently done alot of work involving head surface finishes and am sure my machining meets the 50Ra requirement.Certainly had no problems on prexflow engines.
    After alot of head scratching and asking around people in the know,nobody had ever encountered the problem before.
    My solution? Fitted an Ajusa competition gasket. Pressure test showed no leakage at all. Time will tell.

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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by rollerrocker View Post
    I,ve been fitting cometic mls head gaskets dry for some time on prexflow race engines and my twincam race engine. No problems at all. Until a few weeks back.

    I was building up a twink,I always water test the TC engine before timing the cams up and fitting the sump,water started leaking down the oilway which feeds the head/cams.
    I pressured the system 10lbs approx. and water was seeping out the gasket along the side of the block.
    I removed the head thinking I'd got some crap between the surfaces.When I removed the gasket it was wet all over indicating that the gasket was not sealing round the waterway holes. Hmmmm.
    The thing that I noticed was, on the twink head the oil passage is offset and is linked with a small well .When studying the gasket, which are designed for crossflows, the oval bolt/oil hole has a raised lip to seal oil pressure. This lip does not correspond with the well in the head,hence the water was tracking from between the layers of the gasket to the oil hole.
    I've recently done alot of work involving head surface finishes and am sure my machining meets the 50Ra requirement.Certainly had no problems on prexflow engines.
    After alot of head scratching and asking around people in the know,nobody had ever encountered the problem before.
    My solution? Fitted an Ajusa competition gasket. Pressure test showed no leakage at all. Time will tell.
    Ive always favoured a wire rung block an Reinz gasket over MLS ones, only really due to cost though.

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    Re: Cometic MLS head gasket fitting method

    If the Comectic does not line up with your engine it is of course wrong build up. But I did used some Cometic in "wrong" setup situations also. Again on Jag engines. Later heads on early blocks. Depend the situation you can open the gasket (take all parts separate) and use Hylomar in between all layers. In some situations I use 5699 to seal (as done on Honda S2000 to seal the chain part from the water channels). What will be best depend from situation to situation and here is experiences the main key. If it's your first trial it can go wrong. I can say I can seal almost anything with a Cometic gasket and my proven sealers. If I can't seal it it will not seal with any other gasket. Of course when you don't need a Cometic you are probably cheaper of with a standard gasket.

    BTW, those Ajusa gaskets are not so super anyway, I've tried twice in a Pinto (no extra sealer) and water was running out at all sides. The gasket was not "deforming" between the head and engine. Leaving me with draining water channels.

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    Re: Cometic MLS head gasket fitting method

    Quote Originally Posted by rollerrocker View Post
    After alot of head scratching and asking around people in the know,nobody had ever encountered the problem before.
    My solution? Fitted an Ajusa competition gasket. Pressure test showed no leakage at all. Time will tell.
    .

    Cheers for the response. I like the Ajusa finish as it has a nice "varnish" finish to it that allows a good seal. Have fitted them to Twincams and still going well. The thing I don't like about them is that you have to cut them to get them to fit if using the rubber drain tube, and they don't seem available above 84mm!

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