valve seals on heads question.

[GJCAT427]

The Tunnel port head I have had PC seals on both intake and exhausts. Question can you run umbrella seals on the exhausts and PCs on the intakes with out doing any harm? I keep reading that PCs on exhausts will possibly gall and to use the umbrella on the exhaust for more oil lube. Would this cause a smoker and use more oil than I want? Give me the pros and cons. Guides are cast iron by the way. 

[blykins]

I use Viton seals on every engine, both intake and exhaust.  Cast iron guides or bronze.

[Barry_R]

I also run viton on most stuff both sides.

Some race folk run no seal at all on the exhaust side, and I have done that a couple times when the engine showed a tendency to stick a valve (iron head stuff back in the proverbial day) with no apparent ill effects.