If you recall from earlier post, I have a clearance issue with this ridge and the intake valves…

After much thought I decided to try to fix this myself.  Usually a job for the machine shop, but just couldn’t see dropping likely $400 to have this done.  Little bit irritated that the engine shop let me get into this fix in the first place.  What has to be done is to grind away enough of that ridge to be sure it never comes in contact with the intake valve.

These are intake valves, or at least one end of them.  This disc end needs to be sure it clears that ridge on the pistons.  I’ve cleaned up two of the four here on the wire wheel, did the other two after the picture.  These are OLD valves, not the ones I’m actually using in the engine, so they will serve as drills to grind off the ridge on the piston.

Some two part epoxy to glue sandpaper onto the surface of the valves.

I used a 36 grit sanding belt and glued the valves to a piece of it I had cut out.  I glued two other valves to some 50 grit sanding belt.

Into the vice to set up overnight.

Next day, I put two pistons at TDC and masked them off from the rest of the engine with masking tape.

I happened to have another 20R head lying around, so I put the valve into it, and mounted it on the motor.  With the valve down so it is sitting on the piston underneath, I used a feeler gauge to measure the .07” that I figure I needed for clearance.   .08” is the recommended clearance, and I already had some clearance, just very very little.  Using a Sharpie pen I marked the valve stem where the feeler gauge is.

Mounted my drill onto the stem of the valve.

Now simply drill slowly until the gap between the blue sharpie mark disappears.  Drill SLOWLY.  One revolution a second is about right.  Once the blue mark was down to the valve guide, I pulled off the drill, and removed the head.

Whala, ridge ground down.  Now unfortunately, I used the standard size valve, and the ones in my final built head are oversized by about 2 mm.  So I was hoping for no ridge on the cut, but I got one.  Hard to see, but in next picture, on the upper right of the cut, you can see where the edge of the valve was cutting into the ridge, but not overlapping it.  This area still needs to be ground down, if my wider diameter valve is going to get clearance.

So I went at it the old fashioned way with a file.  Given the contour of the existing cut, I could expand it for the wider diameter valves.

Here it is after I filed it down.  I put the final built head on and using some play dough, checked clearance, and all is happy.  At least as far as I can tell.  Here is a photo of all 4 pistons completed.