340 Valve stem seal preferences?

[tpietzsch]

Working on my 1973 340, any valve stem seal replacement preferences, Umbrella vs. Positive style. Seems the positive style would be better than the umbrella as the positive would wipe the valve rather than just shielding it from oil. Thoughts appreciated. Oh, i looked around in the archives and didn't come up with anything. Maybe it's me but i can never find anything in the search.

 

[moparleo]

Are you rebuilding an engine or having a valve job done ? New valve springs? Or what ?

 

[Chryco Psycho]

the positive seal can starve the valve for oil , it needs some oil & it depends what the engine is used for

 

[tpietzsch]

Thanks for the input i did a little more reading and discovered the head has to be machine to accept the positive seal so I'm going to stick with the umbrella design since the motor is in the car. I'm hoping by replacing these stem seals will solve the occasional off throttle smoking like when approaching a stop sign or coasting around a corner etc. Doesn't smoke at idle or acceleration.

 

[moparleo]

Correct. That is why I wondered if you were having head work done. In order to install the positive seals, the machinist needs to know the lift of the cam and springs being used to know how much clearance the seals need between the top of the guide and bottom of the retainer at full lift. FYI