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Discussion Starter #1
In order to bring a valve shim down to your approved clearance - take a wheel grinder-cutter place it so that the bottom of the wheel faces up-fire it up- and place the valve shim on it with the valve surface been holded down by a screw driver - grind for small periods of time and measure with the dial gauge-voila
 

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If you need to change the size of a shim, 2000 grit sandpaper on a piece of plate glass has always worked for me. If you rub the shim in a figure 8 you can go down a shim size every 10-15 minutes while keeping the shim true.

Joe
 

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Sure, buy why?

Why would you want to grind your shims to thicknesses that are intermediate to the ones supplied by the factory? Why is it important to set the valve clearances to tight specs?

I doubt the valves close that consistently - crud on the valve seats and rotation of the valves in the guides will cause them to land a little differently each time they close. Differing rates of thermal expansion between the aluminum head and steel valve is going to move things around as the engine heats up. So, you might set the clerance to the nearest .00001" on the bench, but 10 firing cycles later everything is going to have moved a little bit.

I can understand "blueprinting" an engine, but jeez...
 

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I agree that valve clearances don't need to be set to NASA type specs. But there are occasions when it is nice to be able to grind down a shim. I'm fortunate enough to have a pretty complete 9mm shim set. But on the race car, I run 8mm valve stems, and my shim set isn't as good. I routinely grind a shim to the right thickness on my bench grinder. Unlike the original poster, I leave the wheel vertical. Put a dab of wheel bearing grease on the end of an old valve stem. Put the shim on and slowly lean it agains the side of the grinding wheel. It is CRITICAL that the shim spin on the valve stem as it is cut. Otherwise it won't cut square! Once you get a feel for it, the process really works well. Again, not necessary if you have a complete shim set. But not everyone does. And by the way, I do know that you can use a 9mm shim on an 8mm stem. I just haven't had to do it yet!

Erik
 

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I am of the old camp that you don't grind a shim unless you have no other options. A .25mm isn't going to make that much of a difference in the big scheme of things. Now if you are down to valve seats that are ready to be replaced and you are having to use a shim less than 1.500 then grinding might be acceptable. Using oil on a 400 grit wet/dry and a glass plate to me is the only way. Usually if a shim doesn't measure square when I rotate it in the micrometer, I toss it. I hate cars that come back after you have worked hard on them because something isn't working right. A $4 (or what ever they cost) shim isn't worth the headaches.
 

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Y'know, in retrospect, these discussions make me wish I'd have picked up that surface grinder the school shop was auctioning off when they canceled machine shop votec way back when I had the chance. (I wanted the CNC vertical mill too, but poverty gets in the way of such dreams. *sigh*)

That would be the precise way to do it.
 

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Discussion Starter #9
joe the sandpaper thing it might just give you psychological problems, the grinder used in very very brief periods is faster
 
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