Is there anything special about YB valves, are the zorst sodium filled, or a special material? I know these are often run at 500+hp, just wondering if the ST170/Zetec valves will take the same abuse.

Rick.

 

YB exhaust valves are sodium-filled.. as are Focus RS... so perhaps Ford know something we don't... Although only the S1 ERST ones were, the later S2 weren't! Cheapskates..

I don't think you'd have a problem really with normal zetec exhaust valves.. at any typical power figures < 500bhp..

 

Even the a series mini engine used sodium filled exhaust valves on some models!!
tabetha