Umbrellas on exhaust..

[Steve V]

My machinest called and said he was having a hard time getting a replacement exhaust valve in the proper material without the oil groove.

He suggested using the OEM valve with an umbrella seal(goes up and done with the valve). He says only down side would be possible smoke at start up.

I said I am not comfortable with this setup since I have never heard about it on a buick head before.

Looking for opinions from experts.......