This has come up on a build thread so figured to keep it all in one place and simple I figured I put up a couple of general points of info incl some important basics to understand the different methods.
A headgasket serves two major functions.
First to retain fluids (oil/water) in their corresponding chanels/pathways.
Second to keep the combustion cycle in the combustion chamber.
Fluids are retained via sealant either applied onto a gasket, impregnated into a gasket or manually put on one like on older motors.
The combustion cycle is retained via a fire ring. Depending on the severity of the combustion cycle would dictate how manly the fire ring has to be.
When looking at a fibre gasket the fire ring is the metal bore ring. Serves it's function well for na motors but tend to perish over the years
More modern MLS gaskets consist of coated surfaces to aid in fluid seperation and then contain internal layers that have the fire ring build into them. When these are torqued down they will indent the block and head to help seal. They function great for higher pressure cycles like FI motors.
Once a MLS gasket has been used you cannot change brand or go back to fibre without skimming the block face as you need to get rid of the fire ring indent.
If you look at cometic gaskets they have a very large fire ring compared to that of oem factory ones.
There is other versions of gaskets but for the purpose of our audi's those will do.
If you end up overboring so large there is no gasket available without cutting into the fire ring of a stock gasket the most obvious option is to use a copper gasket.
Being a soft metal once clamped down between the head and block itwill shape itself to all the contours instantly sealing all water and oil ways. The problem is we have no fire ring
This is where o ringing the block comes into play. A special tool is used to cut a perfectly circular groove round the bores. They cut in specific wire thicknesses which are chosen relative to application.
Once the grooves have been cut a copper wire bought by the reel (much like welding wire) is used to create the fure rings. Layed into the groove they are cut to length so the beginning and end of the wire butt up seamlessly to each other. Once all the bores have been ringed (block only) you can use a copper gasket to seal
Alternatively it has been found that the use of a fibre gasket works like a copper gasket where the o-ring needs to be placed just behind the original fibre gasket fire ring to assist it.
If you went to a total extreme you could do away with the gaskets altogether and use some high temp rtv sealant across the mating surfaces and machine the block to accept gas filled sealing/fire rings like wills rings.
Hope that hels some people
.
A headgasket serves two major functions.
First to retain fluids (oil/water) in their corresponding chanels/pathways.
Second to keep the combustion cycle in the combustion chamber.
Fluids are retained via sealant either applied onto a gasket, impregnated into a gasket or manually put on one like on older motors.
The combustion cycle is retained via a fire ring. Depending on the severity of the combustion cycle would dictate how manly the fire ring has to be.
When looking at a fibre gasket the fire ring is the metal bore ring. Serves it's function well for na motors but tend to perish over the years
More modern MLS gaskets consist of coated surfaces to aid in fluid seperation and then contain internal layers that have the fire ring build into them. When these are torqued down they will indent the block and head to help seal. They function great for higher pressure cycles like FI motors.
Once a MLS gasket has been used you cannot change brand or go back to fibre without skimming the block face as you need to get rid of the fire ring indent.
If you look at cometic gaskets they have a very large fire ring compared to that of oem factory ones.
There is other versions of gaskets but for the purpose of our audi's those will do.
If you end up overboring so large there is no gasket available without cutting into the fire ring of a stock gasket the most obvious option is to use a copper gasket.
Being a soft metal once clamped down between the head and block itwill shape itself to all the contours instantly sealing all water and oil ways. The problem is we have no fire ring
This is where o ringing the block comes into play. A special tool is used to cut a perfectly circular groove round the bores. They cut in specific wire thicknesses which are chosen relative to application.
Once the grooves have been cut a copper wire bought by the reel (much like welding wire) is used to create the fure rings. Layed into the groove they are cut to length so the beginning and end of the wire butt up seamlessly to each other. Once all the bores have been ringed (block only) you can use a copper gasket to seal
Alternatively it has been found that the use of a fibre gasket works like a copper gasket where the o-ring needs to be placed just behind the original fibre gasket fire ring to assist it.
If you went to a total extreme you could do away with the gaskets altogether and use some high temp rtv sealant across the mating surfaces and machine the block to accept gas filled sealing/fire rings like wills rings.
Hope that hels some people
.
