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Knuckleheadtim,
I have several intake valve cups and one has the small vent hole near the rocker box, two others don't. Was the vent hole a factory and/or dealer modification that came later?
Quite honestly, I've ever paid attentionto these holes until I had this leakage problem - in my OWN machine, of course.... I'm not sure about whether or not I should drill the holes in the cups that I'm now installing, as they don't have them. I understand the point about possible conflict in vacuum through the valve versus that in the return tube during the intake stroke. It seems logical and if logic this doesn't fail me, it would seem that venting to the atmosphere should not cause any harm in the intake or exhaust cups.
Because the return tube orifices must be be submerged in return-oil in order to pull the negative pressure needed to empty the cup, they should work during the up-stroke even if the top covers are left off. I assume that this was the way the earlier 'baby food jar' assemblies worked, as there was no air-tight seal. Therefore, by this thinking the vent should be a good thing.
On the other hand, one might argue that by offering no vacuum in the valve cup assembly during the down (intake) stroke, the REDUCED resistance to oil flow past the valve guide offered by the venting might cause more oil to be sucked through the valver guide into the combustion chamber. I would think that the Factory must have worked this out by trial-and-error if the vent holes were added sometime after the closed cup assemblies were added.
This is what I'm vascellating over. Anyone care to offer comment on my over-analysis. Tom Cotton - any input?
I have several intake valve cups and one has the small vent hole near the rocker box, two others don't. Was the vent hole a factory and/or dealer modification that came later?
Quite honestly, I've ever paid attentionto these holes until I had this leakage problem - in my OWN machine, of course.... I'm not sure about whether or not I should drill the holes in the cups that I'm now installing, as they don't have them. I understand the point about possible conflict in vacuum through the valve versus that in the return tube during the intake stroke. It seems logical and if logic this doesn't fail me, it would seem that venting to the atmosphere should not cause any harm in the intake or exhaust cups.
Because the return tube orifices must be be submerged in return-oil in order to pull the negative pressure needed to empty the cup, they should work during the up-stroke even if the top covers are left off. I assume that this was the way the earlier 'baby food jar' assemblies worked, as there was no air-tight seal. Therefore, by this thinking the vent should be a good thing.
On the other hand, one might argue that by offering no vacuum in the valve cup assembly during the down (intake) stroke, the REDUCED resistance to oil flow past the valve guide offered by the venting might cause more oil to be sucked through the valver guide into the combustion chamber. I would think that the Factory must have worked this out by trial-and-error if the vent holes were added sometime after the closed cup assemblies were added.
This is what I'm vascellating over. Anyone care to offer comment on my over-analysis. Tom Cotton - any input?
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