Valve rubber seals

I?ve seen several replies concerning the need or no need for the rubber seal on the valve guides. Several replies have been ?not needed on the exhaust guide, only on the intake guide.? To me this is totally wrong. Imagine there were no seals at all on either guide there could possible be a slight leak at either. On the intake stroke if there is a leak little or no effect is detected. Only a miner leak of more air to burn. Now, imagine on the exhaust stroke. It is under pressure as it is expelled. There too only a miner leak. The problem is the leak here goes into the valve spring chamber and then into the oil pan. At 1,200 RPMs that small leak by the exhaust valve will mount and the only escape is through the oil intake pipe. Most people attribute the blue smoke coming from the oil pipe is due to worn rings. Could be but could be valve guides leaking. I say put the rubber seals on all guides. Agree?
 

The "Leak" that is being addressed is the oil going down the valve guides..not vapor going the other way..

The Intake valve/guide is subject to Suction that tends to draw oil down into the valve-port..

The Exhaust side is not subject to that suction, so the need for a "valve seal" is not as great.

Understand, there are different types of valve seals..the most basic are the "Umbrella type", and the ones used on small-block Chevys that are only a tiny rubber band.
"Perfect Circle Teflon Seal" may do the job too well and also require machining of the valve guide..
 
(quoted from post at 20:17:03 06/25/17)
The "Leak" that is being addressed is the oil going down the valve guides..not vapor going the other way..

The Intake valve/guide is subject to Suction that tends to draw oil down into the valve-port..

The Exhaust side is not subject to that suction, so the need for a "valve seal" is not as great.

Understand, there are different types of valve seals..the most basic are the "Umbrella type", and the ones used on small-block Chevys that are only a tiny rubber band.
"Perfect Circle Teflon Seal" may do the job too well and also require machining of the valve guide..
Your description fits a valve in head engine, not a flat head, I use all four because of, why not.
 
Put em on all guides--can't hurt but might help---and for very few pennies..mine had em on all eight so I put em back on all eight--and no, the exhaust ones were not melted or cracked in any way..
 
(quoted from post at 21:34:22 06/25/17) Put em on all guides--can't hurt but might help---and for very few pennies..mine had em on all eight so I put em back on all eight--and no, the exhaust ones were not melted or cracked in any way..

Sure would not hurt . You have the same hot pressurized gas that can blow out the gasket between the block and the manifold trying to find an easier way out . A little different story than a manifold expanding and contracting but I would just assume stop any gas from pooting past a guide . In a perfect world there would be zero percent leakage but in a used motor being rebuilt with used parts one in a hundred may leak . I don't want that one especially if I had the chance to knock it out while I was in there .
 
I see no reason to seal flathead valves, actually think the upside down cup could hold oil and pump it into cylinder.
 
(quoted from post at 20:10:25 06/26/17) I see no reason to seal flathead valves, actually think the upside down cup could hold oil and pump it into cylinder.
The seals are on the outside of the valve guides not the valves, they are not in any way shape a form a cup. You need to overhaul a N flat head engine.
 
(quoted from post at 21:10:25 06/26/17) I see no reason to seal flathead valves, actually think the upside down cup could hold oil and pump it into cylinder.

Well Duh , you install the cup side down to avoid this problem .
 

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