NBR 70 is exactly what i use for outer O rings
the NBR usually comes also in 2.4 and 2.5 ,, though i dont recommend it for inside O ring duty as there isnt the same buffer for temp that viton has
nitrile is rated to 120 C,, viton is rated to 205 C

- i have however trialled nitrile there myself and the car went for 12 months before failing the groove in one of the plates
( suspect 2.5 was just a little too large for groove in plate style )

just to make it all stunningly easy

- inner 740 mm , 2.4 mm CS per plate surface
( its fractionally long and fills outer edge of groove perfectly )
= 3m for engine


- outer 930 mm , 2.0 mm CS
= 3.8 m for engine
you also need 4 x ( 15.8 mm x 2.4 mm ) NBR O rings for the engine oil passage dowels
and 1 x ( 11.8 mm x 2.4 mm ) NBR O ring for the S5 type timing cover passage
( and nylon insert )

you will find with the length measurements this makes the seal slightly too long
- on purpose,, as you will have to move all of the ring to the outside edge of each groove before it all beds down

-- this will amount to the but joined ends being forced together under compression


- a small amount of silicon in the bottom of each groove before you place the seal will hold it all in place while you stack
( a small amount will squeeze into the engine if you use too much,, but will not hurt anything if you turn the engine over and fetch the cut off out of the exhaust port )
once you get experience up you can get sparing with the silicon and only use a dab here and there to hold the seal in place

- glue ends of the roll with superglue
- you can use superglue on just one end,, and join them
alternate method is to dab both ends in glue, hold together and dust with a little bit of baking soda

( i use the first method now ,, but originally used the second method )
the glue bond is secondary to the compression of the stack forcing the but ends together

0cm2v7 ( 2.0, viton 75 )
0cm2-4v7 ( 2.4, viton 75 )
0cm2n7 ( 2.0, NBR 70 )
0cm2-5n7 ( 2.5 NBR 70 )

0k2setn7 --kits, o ring NBR 70 , set of 5 ( thats the massive O ring kits ! )
( $60 looked after )

ok thems the details for the O rings


NBR is nitrile butyl rubber, or buna-n for WW2 buffs
viton 75 is a newer , better alternative, as discussed above
( has 67% flouro silicon which makes it a newer closer cousin to mazdas special O rings )


here is the sting
nitrile is around $3.70 a metre
- well worth the effort
but due to its -40 to 120 centigrade design temps
you may want to use the RTV silicon to heat buffer it !
( not that i think that the heat range is incorrect, just not any buffer ! )


the viton 75 is MUCH more expensive at $20 a metre
but handles -30 to 205 centigrade
but , doesn't work out cheaper for the outer ring ( maybe select NBR there for 2.0 )
and works out only around 50% of a saving over mazda inners
- but will be physically more compression resistant ( and by reports reusable )
more chemically resistant
equivalent in heat resistant
more tear resistant
and prouder for less true housings

the number code used signifies hardness [ shore test A ]
and you can get NBR and VITON in 90 !!
http://www.transeals.com.au/seals/datas ... -rings.pdf
order by quoting the dash number ( imperial ) or the metric size, then material
specify ID, then CS ( inside diameter of ring, cross section of rubber )

using a little silicon as holding helper is not as messy as it sounds !



this is a viton glue join
and it joined easily and strongly
( stronger than a laminated OEM inner seal join )
its cut straight and glued with black and gold super glue !

just to make it all stunningly easy

- inner 740 mm , 2.4 mm CS per plate surface
( its fractionally long and fills outer edge of groove perfectly )
= 3m for engine


- outer 930 mm , 2.0 mm CS
= 3.8 m for engine
you also need 4 x ( 15.8 mm x 2.4 mm ) NBR O rings for the engine oil passage dowels
and 1 x ( 11.8 mm x 2.4 mm ) NBR O ring for the S5 type timing cover passage
( and nylon insert )

using charts i have supplied above, it wont be hard to suss the rear stat O ring
and oil pedestal O rings

which brings rebuilds down to bare minimum OEM front and rear seals and timing and inlet and exhaust gaskets
( and pickup gasket )

edit ,, o ring length reviewed 4/10/2009 to be fractionally longer
- push o ring to outside of the track to make the longer lengths fit

buna-N ( butadene natrium )
= brand name for NBR = Nitrile butadiene rubber
rated for -40 to 120C
commonly sold as NBR-70 ( shore hardness test A = 70 ) ,, but can be got in NBR-90

buna also comes as buna-S
= styrene butadine rubber which is rated to from -40 c to 100C
with a shore A test hardeness between 50 - 90


viton is a flouroproylene and is rated -30 to 205C
and comes as viton 75 ( shore hardness test A = 75 ) or viton 90 ( shore test A = 90 )

I also have a solution for the tension bolt seals.

Also on the outer coolant seals, the factory ones get stretched. I just simply cut them back down to size and silicon them together. Lastly in that link I posted above, I'm gonna try the viton square cord this time around (2542T21) for the inners. They are the same size as the 2.4mm rounds but cost a little bit more. That should give me more sealing area.