paul
aren't the valve stem seals just something extra?
if the valve stems and guides are in good shape
whatever oil gets down there is nothing?
that little bit just gets burned up with air/fuel?
i never use a PVC valve.
i think any horror stories you hear are because
the rings are letting compression get into crankcase.
Have A Nice Day!
The valve seals you would think are just somthing extra,,but valves are not fitted to the guides as tight as one might think. Even with fresh guides they dont stay to tight of a fit for long. With the side loading the rockers put on the valves as they are pushed open, that alone wears the guides. On the intake valves the suction of the piston drawing in a fresh intake charge will draw oil into the chamber past the guide. Many racers dont even bother putting seals on the exhaust valves, on drag engines only.
The importance of good seals on intake valves depends on a few things. If the guides have liners, they need good seals. If they guides have been knurled to tighten the clearance to the valve stem, they need good seals. If the heads have had either of these things done, the oil will run right down into the chamber, especially if the guides have been knurled.
What I mean by good seals is the type the push down over the OD of the guide.
These have a band clamp to hold the secure to the guide. The umbrella type seals just slide down over the valve stem. That type are ok in pure stock motor, but add a hi lift camshaft, and those type get pushed up the valve stem towards the retainer. As the valve starts to open, the seal only sheids the guide when at full lift.
Valve seal installation must be done with those plastic condoms that slip over the valve stem to prevent the seals from being damaged from the grooves machined for the valve locks. Many guys think they can just grease up the end of the valve and push the seals on, bad move. You will have a damaged seal.
Check out the seals from companys like Crane, Comp Cams, you will notice they have a band clamp to keep the seal clamped to the guide, and the teflon seals have a coil spring like deal that clamps the seal to the valve stem. These are seals for race engines, and may not be what your looking for, but will give you a better idea on whats out there for extreme applications.
Even look at what GM uses for seals these days. They havnt used those o-ring type seals for years. The use a seal that pushes down over the guide to keep the majority of oil out of there.
Don,t forget that in todays Hi-Perf engines, most are using a oil pump of hi-pressure, and hi- volume. That will send alot more oil up to the top end. Though many race applications will use restricters to limit the oil sent up to the top end with roller cam/roller rocker combo,s , the oil thats floating around in the valve covers does have direct effect on valve spring life. The oil helps cool the springs.
So a modded oil pump, or a purpose built oil pump will send more oil up to the top end. Thats reason enough to have the best seals you can get your hands on.
Also, the seals that push down over the guides have to be most times the guide od be machined to to except this type of seal. Take a look at Moroso, Mr Gasket, for the tool that cuts the guides down. Simple tool that has a arbour that drops in the guide, and is mounted in a regular hand drill. The last one I bought was about 40.00 bucks, and you can update the heads to the good stuff in less than a hr.
I dont know exactly what your build up is, but I can say this about oil making its way in the combustion chambers. On a hi compression race engine, it will invite detonation, and that will destroy a engine in short order. Best to keep the oil out of there.
Paul