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Author Topic: Cometic MLS Head Gaskets  (Read 2198 times)
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WestonE
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« Reply #20 on: April 13, 2017, 10:10:30 AM »

Beta Fans

If you would like one or more of these gaskets by the end of May I need your order by the end of April stating how many and what thickness. Payment will be by bank transfer to me to include 7 P&P for the UK. Please PM me with your delivery details. I hope that is clear?

You will need to install a heater pipes H section and use new head bolts/ studs I will help with torque settings. These gaskets can be re-used if installed correctly. They must NEVER be re-torqued hot.

Thank you

Eric   
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Deltona
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« Reply #21 on: November 20, 2017, 07:11:49 PM »

Just an update to say I have received reviewed and made minor corrections to the design Mylar. It will now be sent back to Cometic next week and travels to the US for production in early February so hopefully pricing and availability soon.

Eric   

Who or what is 'Mylar' and who is the UK outlet for Cometic please?
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mangocrazy
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« Reply #22 on: November 20, 2017, 10:55:56 PM »

If you want a Cometic head gasket for a Beta, then Eric (WestonE) is your man...
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1980 Lancia Beta Spider 2000 (S2FL)
2002 VW Transporter T4
2008 Aprilia SL1000 Falco
1992 Ducati 888 SP3
1988 Honda VFR750F
Deltona
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« Reply #23 on: November 21, 2017, 04:46:18 PM »

No it isn't for a Beta, I just wanted to know where their UK outlet was, but it's ok, I've found out now.
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Deltona
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« Reply #24 on: November 24, 2017, 12:16:10 PM »

1.7mm for standard compression 1.5mm for typically 1 point higher on compression e.g. 10:1 to 11:1
  

I think there is something amiss there, but as the vital parts of the equation missing I can't check.
.2mm difference shouldn't give a whole point in CR?
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WestonE
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« Reply #25 on: November 24, 2017, 07:06:53 PM »

CR should be calculated by measuring all of the components in the individual engine and applying the formula which is extensively published on the internet. It gets much harder to do with domed pistons of course unless you have the dome area supplied by the maker. Gasket thickness has move impact than most people realise, but then deck height is also frequently not properly considered. There is also squish to be considered with pressure charged applications where it can help to reduce detonation at the expense of cross port flow.

If you want a Cometic MLS Gasket for a reverse head engine you need the Delta versions available from Delta parts/ Burton Power/ Demon Tweeks and others or you will find the coolant metering holes making the inlet side too cold and overheating the exhaust valves on the other side.

I spent many careful weeks working with Cometic to develop these gaskets to help my extreme Volumetrico Supercharged Montecarlo engine build. In the process Beta owners have the opportunity to use a vastly better head gasket.

Eric     
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Deltona
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« Reply #26 on: November 25, 2017, 01:17:38 AM »

Lets do the maths on an engine where the pistons are 1mm proud of the block at TDC and:
85mm bore
85mm gasket
Combustion chamber volume 50cc
90 stroke
Flat top piston (no valve cut outs to keep it simple)

With a 1.7 gasket we get a CR of 10.46
With a 1.9 gasket we get a CR of 10.26



Now lets add a domed piston where the dome is 10cc in volume:

With a 1.7 gasket we get a CR of 12.61
With a 1.9 gasket we get a CR of 12.32

Here we can see that there would be 0.1 difference in the results from a dome to a flat top therefore a 0.2 difference in HG thickness gives an increase of between .2 and .3 in CR.

You wit' me?
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WestonE
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« Reply #27 on: December 09, 2017, 05:11:48 PM »

OK happy engine builders just in case you did not know you need to measure CR in building your performance engine try this for a guide to how

http://blog.jepistons.com/how-to-calculate-engine-compression-ratio-and-displacement

Note the importance of the block deck height and combustion chamber volume and how these can vary with skimming in refurbishment.
 
please also consider piston to head and piston to valve clearances verified by dry build checks as nicely described in all generations of Guy Crofts books.

Enjoy

Eric

 
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