cometec why 106 for 104 and FMJ???928 HG
01-23-2010, 11:17 AM
#16
That Guy
Rennlist Member
Rennlist Member
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.
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.
01-25-2010, 07:16 PM
#17
Former Vendor
Info straight from the horse's mouth:
Hope this helps
- Last fall, Cometic revised all of the tooling to the latest embossment designs, so the 944-specific gaskets are all ready to go.
- Any of the gaskets are available in ANY of the standard thicknesses, .027" and up (I need to revise the listings on my site accordingly)
- MLS gaskets can be ordered in piston bore size, and the default practice would be to allow for .015" clearance, unless specified otherwise. So with the standard tooling, a 2.7L gasket may be ordered with 104mm bores, no problem. If you want more than .015" clearance, just specify when you order. The reason some gaskets are larger than stock bore is because they were based off of stock gaskets (e.g., the 924 2.0L 88mm bore gasket), which accommodate both STD and OS piston bores (e.g., the 924 2.0L 86.5 STD, 86.75 1st OS, and 87.00 2nd OS).
- Regarding sealants and coatings, my source was emphatic that they are absolutely NOT required, but that some old school guys still use them because (as he put it) "old habits die hard"
Hope this helps
01-26-2010, 04:44 AM
#19
Nordschleife Master
I've run a 106 mm gasket on a 100 mm bore... It was the only size the fancy Phuzion gasket's came in at that time. But it held for high power and abuse for at least 7000-8000 km's....