I recently replaced my dried out cracked valve seals on my v6 2.8. I've been wanting to ask this question for a long time about those simple style oring valve seals you find on chevy engines. My intake valve seals consist of a combination of a cup or umbrella style seal along with an oring on the top. My exhaust valves only has the orings. But if memory serves me right, I remember my old 350 only having the oring style valve seals on both intake and exhaust. If you wanted cup styles, you would have to machine the guide to accept the cup seals......Anyways my question is how the heck do those little oring seals work when they're way up there on the valve stem? I don't see how it makes contact with the guide on the down stroke? Thanks for any explanation.

 

The best I can make out on the O ring valve stem seals is that they deflect some of the oil running down the valve stem, being that the the Chevy engines really send a ton of oil to the rocker arm area, but I just guessing. Some really old engines used no valve stem seals at all and worked just fine, then again they used much heavier oil.