gt37vgt

I'm buying a head gasket for a 104mm engine I'm throwing together .
Three things I'd like to discuss in this thread

1 Why has Cometec got 100 and 106 listed for there 944 head gaskets??
there really is not that many 105 and 106mm overbore out there is there ?

2 Discuss the difference of the 928 head gasket .. it comes in 104mm and you can see buy looking art 16v head it is made to either way for a V8 so ther is alot the same there ....

3. I did a search and found and old thread referring to a gasket as "FMJ"
Full Metal Jacket that was available with an integrated o ring for 170$
and not seen anything else is there .. Is there gasket that is something better than regular cometec but cheaper than cometec Phuzion ??

ideola

subscribing

Chris White

You can get the Cometic gasket in just about any size you want (thickness and bore diameter). They only list a few sizes in the catalog. And yes, some of us have 106mm bores!

Cometic used to make a “HP” gasket that was made with a slightly thicker area around the cylinder – its been discontinued.

ideola

The thing I'm puzzled about is why they don't list 104mm for 944...

...be careful on thicknesses, though...beyond .051" and you're talking about a 5-layer, which adds a little to the cost...

gt37vgt

yeh perhaps the over bore crowd was buying up before more than the 104 mm crowd... I guess every 106 mm guy is gonna chose a cometec but not every 104mm will choose cometec ..just puzzled as i know the 104mm engines out number the 106 by a long way ..

ideola

And after reading some of the other threads on this topic, I defintely want to confirm with Cometic that they have the 944-specific version with the 104mm bore. The 928 setup is NOT sufficient for the 944. The stuff listed on my site is what they told me was available...and for what it's worth, the info they gave me is more comprehensive even than their own website. This isn't something I want to take a chance with. Better to get it straight from the horse's mouth. I'll get to the bottom of it on Monday.

gt37vgt

ok i see the 928 has no water recirculate port at all is the difference .. i could probably use it as I'm blocking that off and using an electric water pump
http://images.google.com.au/imgres?i...GdCgkQX-svWVAw

ideola

I would hold off, though, because I read a couple of threads that indicated the 928 gaskets weren't sealing correctly on the 944, so Cometic came out with a 944-specific one.

Chris White

Maybe its just me…..but if you are not that familiar with the Cometic gaskets do you really want to be selling them?

There are some important things to know about how to spec and how to install them. For example – you DO NOT want a 104mm gasket for a 104mm bore (or a 100mm gasket for a 100mm bore).

gt37vgt

Chris please explain a bit further as this is what the thread is about ...
do they list as engine bore size ?
or gasket hole size ...
if the listing was 102 and 106 that makes sense
or listed as 100 and 104 that also makes sense iven if one 2mm bigger arrives ..
why would they be any more than .5 bigger then the bore ...??

ideola

Chris, I am quite familiar with Cometic. I personally commissioned the 88mm bore gasket for the 86.5mm bore 924 2.0L cars, which was never before available until we undertook it as a project and hounded Cometic until they produced it. I personally toured their facility, and dropped off my own block and two heads, one for the NA and Turbo applications to make sure a correct, multi-use gasket was produced. Subsequent to the first run, we discovered a very minor, non-critical fitment issue due to the rivet tabs, which has subsequently been corrected. So I am plenty familiar with Cometic.

My experience is that they list the bore size of the gasket. For example, on the 2.0L platform, the gasket is listed as 88mm, while the bore can be anywhere from 86.5 out to the max bore of 87.5mm.

Chris White

gasket hole size.
They will make just about any size you want - but if you ask for a 104 you get a 104. You want the gasket to be at least .5mm larger than the bore.

You should also be familiar with the Ra finish of your head / block. Tossing a Cometic on an old used head / block is asking for a failure.

And then there is the torquing procedure....and gasket coatings....

Chris White

Sounds like you are more familiar with the Cometic gaskets than your previous questions would indicate!
The Cometic gaskets have been getting a little bit of a bad rap from some of the 944 crowd – but most of the problems are due to incorrect installation / prep work. So when I read the pervious questions it seemed that you were not very familiar with the product. No harm intended..!

ideola

No worries...the instructions we've received, which we passed on to all of the 2.0L recipients, is as follows (and is posted on our website):

• A surface finish of 50 RA (roughness average) or finer, is recommended for a proper gasket seal. Anything rougher may conflict with the gasket design.
• The MLS gasket CANNOT be used with o-ringed blocks or heads, because the o-ring would interfere with the embossments. Probably not an issue on the 928/944 platform, but o-ringing has been standard practice on high-boost 931 applications.
• Head torque specs remain the same as OEM
• Contrary to some information on the internet, Cometic does NOT recommend the reuse of MLS gaskets

Cometic did not give us any specific instructions with respect to coatings, so I am definitely curious to get their feedback on this. It may have to do with the fact that the 2.0L platform has block and head with dissimilar metals, unlike the 928/944.

I totally agree that putting an MLS on a non-worked head and block would be a really Bad Idea, and also that making various bores should be no big deal since they already have the rest of the geometry.

Chris White

There are a lot of Oringed 944 heads out there...and yes, they don't work with the Cometic gaskets (I did resurface an O ringed head with the Oring in place for one customer - he had a lot of work in that head and really wanted to use it. you need very sharp tooling to make that work!)

Cometic recommends against any coatings….but a thin coating of RTV on all the layers around the coolant ‘ear’ in the front sure helps!

If you reuse on (and yes, it does work) a little copper coat is not a bad idea if the original coating is worn. Typically I would like to use a new gasket….but sometimes you have to work with what you got!

The best practice for torqueing is to torque to 50 lbs, leave overnight and then retorque. To be completely correct you should retorque the head after heat cycling it a couple of times.