Time to check on the heads. After some cleaning we see that there is some pitting in the flat areas inside the combustion chambers. I ground and sanded down past the pitting to make a smooth finish. This left the ring around the inner edge where the cylinders seat too high and there was some pitting here too.
In the next series of pictures I illustrate the process I used to mill these down to the right height and make sure all three are the same level so the cylinders will seal properly.
These two pictures show the top and bottom of the jig I made to route the face of the head. There are four screws up through the bottom ( right pic ) for leveling the head in the jig relative to the cylinder lands.
One head is secured in place in the jig ready for leveling
I now make sure that the cyl lands are level with the top of the jig using the adjusting screws under the head. I want it level in all directions.
My router is attached to a flat, 1" thick board covered top and bottom with arborite. A 1" carbide bit projects through to the level of the head and is passed over it cutting the surface flat and true with the inside of the cylinders
The head face is now flat and ready for the next step.
What we are going to do now is make a " gravestone rubbing" of the top of the head. Carbon paper is placed on the head carbon side up. A sheet of paper goes on top. The roller you see in the forground is pressed down on the paper and rolled across. The pressure causes the carbon to deposite on the paper in the pattern of the head's face, as can be seen in the right picture. We now have a template for the next step.
Now we transfer the centers of all the holes and cylinders to a 3/4" sheet of Ultra High Molecular Weight plastic (UHMW). The areas where lines are to be scribed are drawn out with a large felt marker to make the lines more visible.
All the neccessary holes are drilled out on my trusty plumbing pipe and washing machine parts drill press. This thing is 35 years old and has never missed a beat. The winch on the bottom is for raising and lowering the table. The center to post width is 18".
Next the cylinder holes are roughed out. Yes, you sharp eyed devil, the
vise is on the "wrong" end of the bench. It's that way for a reason. I'm left handed.
The UHMW plates are bolted to the heads, trued flat and a router bit with a ball bearing guide on the bottom is run around the cylinders to cut the plastic flush with
the cylinder sides.
That bit is changed out for an end mill, a cutter with teeth on the end, not the sides. This is run around the head holes in three consecutive passes to make a smooth, flat, level surface on the outside edges of the combustion chambers where the piston cylinders will sit.
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That's it for now. All the engine parts have been preserved with
a " fogging oil " as I want to work on the plane so it is closer to finished before putting the engine together.
