are stock valve seals ok
 

are the stock type valve seals ok for .520 lift cam with single spring ? if not are they called viton seals I'd need ?
this is for a 906 big block head.
also what cc are 906 chambers ? thanks guys .

Yeah you can use them. make sure you got enough room between the spring retainer and the top of the valve guide boss at full lift. I would just use them on the intake valves. Stock type are called umbrella seals, are made of rubber and will last for a couple of years at least. I believe the viton seals {someone correct me if I'm wrong} need some type of machining to the top of the valve guide boss. My bud used the stock type on his motor with a .509 mopar cam. Supposedly, the stock seals are not recommended but usually if you can fit them i see no problem. The problem arises when there is not enough clearance between retainer and valve guide boss [when using high lift cam], this is why you got to measure. If you got to cut down the valve guide boss then you might as well go to the other type of seal, its easy to cut the boss for the clearance and the other type of seal at the same time. Not sure about how much clearance you'll need for the stock seal. Gotta measure. The viton seals stay on the [Machined] valve guide boss, does not move. The umbrella type moves up and down with valve. {lotta cam for single springs though, what pressure are they?}

I am not sure about what the cam has to do with valve seals??? Ya kinda lost me on that one. I have used Viton seals in my Harley heads for years. As long as they fit good and snug around the guide and installed with a driver of sorts ( home made tool ) I have never had a problem with Viton.

ps: If there is something Iam missing here, let me know, thx

906 are 79.5 cc the factory claims.. seals are seals i thought? viton seals are the "O" ring type right?

Ya, actually I think Viton is the material that they are made from.

thanks guys
the reason i ask is i already have umbrella type seals in my felpro gasket set . & when i port my heads i will be using 1.6 ratio cheap ss roller rockers ( brand ? ) with my existing purple camshaft & springs for more lift . i don't know my lift height yet , i'll put a dial gauge on my lifters when the time comes . if its a 484 lift cam with 1.6 ratio rocker that will make it about .514 lift & keep the same duration . & while my heads are getting the seats cut for the new bigger valves i might getem to cut the guides to suit the viton seals also . just so i have less issues .