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Seems I need to clarify what I'm attempting to do here. Yes, a proper performance modification upgrade of the valve and valve seat set are beyond my capabilities. I'm also not going after race car quality modifications at this point in time on this car. What I am attempting to do is more a "cleaning up" of the valve and valve seat mating surfaces. I've seen that proceedure described as grinding (or lapping) elsewhere. Having dug into the innards of a replacement 8V cylinder head as I have is more exploratory - to see how much I can do with readily available tools and methods.
Here's what I've noticed so far. I did just one intake valve last night. With the aid of a magnifying lens I saw that even with a head in very good shape with 100K miles the valve seats showed some wear in the form of pitting along the specific point where the valves and seats actually make contact. Mind you, the pitting is only visible under a magnifying lens. The intake valves also had some rust along the back surface, or the intake manifold side. I'll surmise that the rust and pitting were related given that both valve and valve seat are made of steel. I noticed further that the mating surface angles of both the valve and seats are not exactly the same. That means the actual contact point is a thin line rather than the entire flat angle surface. Where that line is, at least on the intake valve I worked on, was along the bottom (if looking down at the cyl head combustion chamber ceiling) of the valve seat, along the angled edge point.
Using the method I described in the intial post about affixing the rotary drill mounted rubber sanding disc (cut to size) to the top of the valve and using a fine grinding paste along the mating surface - I gave the valve a good spinning for perhaps 45 seconds, then examined the results with a magnifying lens. I saw that the contact point was now even more clearly marked on the valve, and the corresponding contact point on the valve seat - previously a thin sharp edge - had been rounded somewhat, thus creating a larger mating contact point overall.
Having examined the small mating surface condition before and after the grinding, I can only surmise that it is an improvement. A clean, enlarged mating contact surface instead of the small and pitted surface. Of course, having done this, there is the possibility that the valve/cam lobe clearance has been altered beyond spec requirements. I'll be sure to measure the clearances after head reassembly and adjust the shims accordingly.
posted by 152.163.189...
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