[Bored&Stroked]

The original Ford guides from 49 - 53 has a "solid" guide on the exhaust side - there was no place to put a seal. Also, as the exhaust is under positive pressure, you don't have the issue you have on the intake side where the vacuum pulls oil from the valley into the port.

Sealing: The carbon from combustion will "seal the guide" on the exhaust side anyway - so the seal won't accomplish anything.

And lastly, I like the solid exhaust guides as they do a better job of transferring heat from the exhaust valve into the cooling system (due to a larger contact surface area between the guide and the guide bore)..