Hey i got this 350 chevy engine, im going to replace the valve stem seals, now theres like a few diferent types of seals, (material). My question is which one is the best one? or reliable? and is the seals the same for intake and exhaust valves? these are the different materials there is for valve seals:
ruber
teflon
viton
nylon
Some one told me that umbrella type are good, because they cover all the area.

 

Viton.

 

+1 on Viton.

 

Does the heads need any machine work to put Viton valve seals? or do the install just like a OEM part.?

 

I would say teflon or viton. More than likely you will have to get machine work done for them to fit. For sure with the teflons.