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Thread: Cometic MLS Head gaskets.

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    Bodger

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    Cometic MLS Head gaskets.

    So, im in the final stages of a Cosworth n/a engine build.
    Using Farndon rods and Wossner raised top pistons. The head has had a skim or two and currently working out compression ratio. Im aming for a sensible 10.5:1. Its not a big power engine.
    I see Burton do a range of MLS head gaskets right up to 140 thou. Selecting a thick gasket would give me some adjustability in getting the correct ratio. I havent done the maths fully yet but recon Im going to need a thick gasket.
    The other option is machining the piston valve pockets but would rather not if I can avoid it as calculating true volume can then get complicated.
    Has anybody had any experience with these thick Cometic gaskets? My thinking is they must be sound otherwise a good reputable company like Cometic wouldnt make them.
    Lastly are they re-usable or is it a myth? internet search has mixed opinions, Again any actual real proper experience anybody?

    Thanks in anticipation.

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    Re: Cometic MLS Head gaskets.

    probably not the answer your looking for, but its better to machine the piston intruder down than use a really thick head gasket, the intruder gets in the way of the expanding flame front, effectively giving two poor shaped combustion chambers

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    Bodger

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    Re: Cometic MLS Head gaskets.

    Ah, So dont machine the valve pockets instead take some of the actual piston top?

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    Re: Cometic MLS Head gaskets.

    Quote Originally Posted by fingersnfumbs View Post
    Ah, So dont machine the valve pockets instead take some of the actual piston top?
    correct, if you have enough valve piston clearance take material from the intruder first. 6mm crown thickness in the middle is enough

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    Re: Cometic MLS Head gaskets.

    Are you using some very mild fast Road cams because if not I would be looking for a minimum of 11.0.1. Once the intruder has been machined there's no putting it back to increase compression so caution's the name of the game. A thick gasket's not answer either.

    We ran NA Cosworth engines for over a dozen years back in the 90's and we experienced all sorts of problems along the way including finding suitable pistons and head gaskets at the time.

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    Re: Cometic MLS Head gaskets.

    Very interesting.
    Cams are fairly mild Newman PH2/3 288 410. I want to stick with hydro lifters and they are about all I can find with decent lift/duration. High revs a really not my thing, torque and drive is what Im after.
    I have had issues with pinking before and very cautious about going there again. It was a very expensive experience.

    Has anybody re-used MLS gaskets, they are crazy expensive.

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    Re: Cometic MLS Head gaskets.

    MLS gaskets wouldn't be my preference for an engine that gets torn down often! MLS maybe ok for one re-use but the more they get crushed the less they seal and a blown gasket can cost a lot more than just the cost of a gasket! Maybe old skool but for a engine that needs frequent tear downs I'd say you can't beat a re-usable soft copper gasket with or without fire rings! Good MLS are expensive for a reason - supposed to be fit and forget!

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    Re: Cometic MLS Head gaskets.

    MLS can be re-used...if you're desperate. And none of the coating on them is damaged, and if they're in good order...etc etc.

    Really it would be a last resort re-using them though.

    And MLS being expensive or cheap....is largely down to volume and the market. OEM GM LS gaskets are very cheap, and very very good, because they make a gazillion of them.
    Aftermarket companies doing small runs like Cometic and the YB are expensive for the same reason the WRC composite or whatever it is is expensive. Because it is low volume.

    And yes, certainly on boosted setups with MLS gaskets and alloy head or block. A severe head gasket event can torch the head. That rarely ever happens with a soft or composite gasket. I'd doubt it be the same risk on n/a though ?

    Does a n/a build really need or benefit from MLS ? I doubt it
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    Re: Cometic MLS Head gaskets.

    in N/a application i dont see the need for a MLS unless you have to have one for thickness reasons, everyone i know says you can reuse then but doesnt unless desperate, although i keep the old ones just i case i have never reused one

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    Re: Cometic MLS Head gaskets.

    Quote Originally Posted by fingersnfumbs View Post
    Very interesting.
    Cams are fairly mild Newman PH2/3 288 410. I want to stick with hydro lifters and they are about all I can find with decent lift/duration. High revs a really not my thing, torque and drive is what Im after.
    I have had issues with pinking before and very cautious about going there again. It was a very expensive experience.

    Has anybody re-used MLS gaskets, they are crazy expensive.
    Those cams are 288 degrees duration and 410 though lift so I don't see why 11.0.1 compression should be a problem if your ignition advance's set correctly and you use Super unleaded fuel with the correct jetting of your carbs.However if you feel happier with a slightly lower CR then go for that.

    I have never had any experience with MLS gaskets on alloy heads, only cast to cast. I don't consider them to be mega expensive when you look at the cost of other parts. As ST has said, small production cost are much more expensive than components knocked out in their thousands.

    I always found the NA Cosworth engine very disappointing on bother power and especially torque, I hope yours proves me wrong. You have to spend a lot of money just to get them to the std of a good Pinto, let alone better.

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    Re: Cometic MLS Head gaskets.

    Agree with you there FR but Im hoping torque will be up a bit on a standard Pinto.
    Truth is, I already had the cylinder head, cams and inlet manifold so cost so far arent that much. Twin 45 I already have on the Pinto so by carefully selecting component it shouldnt be a silly expensive build for little gain over a good Pinto.
    We will see.

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    Re: Cometic MLS Head gaskets.

    Quote Originally Posted by fingersnfumbs View Post
    Agree with you there FR but Im hoping torque will be up a bit on a standard Pinto.
    Truth is, I already had the cylinder head, cams and inlet manifold so cost so far arent that much. Twin 45 I already have on the Pinto so by carefully selecting component it shouldnt be a silly expensive build for little gain over a good Pinto.
    We will see.
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    Re: Cometic MLS Head gaskets.

    thumb:

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    Re: Cometic MLS Head gaskets.

    Quote Originally Posted by fingersnfumbs View Post
    Agree with you there FR but Im hoping torque will be up a bit on a standard Pinto.
    Truth is, I already had the cylinder head, cams and inlet manifold so cost so far arent that much. Twin 45 I already have on the Pinto so by carefully selecting component it shouldnt be a silly expensive build for little gain over a good Pinto.
    We will see.
    torque wont be up much if at all, at low rpm it will probably be down on torque, the issue is unless you have a really extensively reworked head with a lot of airflow ( most dont) the yb head is hardly any better than a good pinto one which is most are stuck n/a yb at around 220bhp

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    Re: Cometic MLS Head gaskets.

    Quote Originally Posted by fingersnfumbs View Post
    Agree with you there FR but Im hoping torque will be up a bit on a standard Pinto.
    Truth is, I already had the cylinder head, cams and inlet manifold so cost so far arent that much. Twin 45 I already have on the Pinto so by carefully selecting component it shouldnt be a silly expensive build for little gain over a good Pinto.
    We will see.
    torque wont be up much if at all, at low rpm it will probably be down on torque, the issue is unless you have a really extensively reworked head with a lot of airflow ( most dont) the yb head is hardly any better than a good pinto one which is most are stuck n/a yb at around 220bhp

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    Re: Cometic MLS Head gaskets.

    Quote Originally Posted by Graham View Post
    torque wont be up much if at all, at low rpm it will probably be down on torque, the issue is unless you have a really extensively reworked head with a lot of airflow ( most dont) the yb head is hardly any better than a good pinto one which is most are stuck n/a yb at around 220bhp
    im always hearing this, and have not done much at all with YB's so don't know the geometry - whats the downfall of the YB in n/a? compared to say an XE? valve angle maybe?

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    Re: Cometic MLS Head gaskets.

    Quote Originally Posted by onecamohv View Post
    im always hearing this, and have not done much at all with YB's so don't know the geometry - whats the downfall of the YB in n/a? compared to say an XE? valve angle maybe?
    Its a head designed for forced induction where flow is not the primary concern. Want more airflow - up the boost. Strength and heat dissipation usually more important. Yes 'turbo' heads can flow more but there are fundamental compromises in the design that cannot be got round by simple grinding and flow work. I'd guess if you wanted to spend some money, changing the 'side draft' style inlet ports to a more 'down draft' direct shot at the valves would help but its a lot of work!

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    Re: Cometic MLS Head gaskets.

    Quote Originally Posted by onecamohv View Post
    whats the downfall of the YB in n/a? compared to say an XE? valve angle maybe?
    Port angle in relation to valve angle is very shallow like a pinto so air shoots straight across the back of the valve like it does in a pinto, thats not an issue when you have a turbo pushing the air in, but you really need a steeper port angle so the incoming air flows all around the valve.

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    Re: Cometic MLS Head gaskets.

    thanks gents, seems a bit nonsensical to go to all the cost and effort of a yb if the inherent design is poor for n/a. sorry for derailing the the thread but having never done any i always wondered why yb's always fall short of expectations

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    Re: Cometic MLS Head gaskets.

    Believe it or not Cosworth actually sold a NA head back in the early nineties, whether it was just a ported Turbo head or not I never managed to find out.

    I have seen and had some nicely modified Cosworth Heads for NA over the years done by people like Millington and Gardner and they were a work of Art. All heads only ever used Cosworth profiles like L1, DA10 etc. We would have liked to have tried some more modern profiles but no engine builder wanted to foot the expense for development.

    One of the problems especially with engines around the two litre capacity was getting the compression high enough. Due to nature of the head design the valves ran very close to the pistons so that required large pockets to accommodate higher overlap cams which in turn lowered the compression. To compensate for that a big ugly intruder that went into the chamber was used which in turn altered the flame travel for the combustion.

    Getting the right combination of parts to work and produce good figures with that engine was like walking in a Minefield.

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    Re: Cometic MLS Head gaskets.

    Believe it or not Cosworth actually sold a NA head back in the early nineties, whether it was just a ported Turbo head or not I never managed to find out.

    I have seen and had some nicely modified Cosworth Heads for NA over the years done by people like Millington and Gardner and they were a work of Art. All heads only ever used Cosworth Cam profiles like L1, DA10 etc. We would have liked to have tried some more modern profiles but no engine builder wanted to foot the expense for development.

    One of the problems especially with engines around the two litre capacity was getting the compression high enough. Due to nature of the head design the valves ran very close to the pistons so that required large pockets to accommodate higher overlap cams which in turn lowered the compression. To compensate for that a big ugly intruder that went into the chamber was used which in turn altered the flame travel for the combustion.

    Getting the right combination of parts to work and produce good figures with that engine was like walking in a Minefield.
    Last edited by Forest_rallying; 15-07-2021 at 17:44.

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