By Jason Ballamy 
Part five - cylinder and cylinder head
M4. C4n

The next job is to join the cylinder/liner assembly to the base. There was a bit of a difference in the diameters of the two castings so I milled the worse away while it was easy to get at.

There are a couple of options for the joint, I opted for the three pointed grub screws, the positions were spotted through from the tapped holes in the the base and then drilled 0.030" nearer the flange with a 90deg spotting drill. By shifting the hole in this way the grub screw will pull the joint up tight as it screws into the conical hole.
A few drops of 648 loctite around the liner and screw threads and it was screwed together for good.
The mounting face for the hopper was then machined to the correct height and the hole for the cylinder oiler drilled and tapped.
I then turned the assembly on its side and machined the push rod bosses back to height and cleaned up their sides at the same time. The boring head was used to cut a flat surface for the ignitor to bolt to.
And a quick test to see how the rod fitted (I'll describe machining the bronze brackets later).
A pocket was milled for the ignitor points and a hole drilled through into the combustion chamber.
The final job was to drill the 1/16" oil hole down to the cylinder at an angle.
The next logical part to tackle was the cylinder head. This is quite a simple iron casting consisting of basically a disc with two spigots on one face for the valve guides and a boss on the edge for the inlet & exhaust.

I spent some time accurately locating the centre so that the valve spigots would be in the right place then clocked the casting in and machined the cylinder mating face and spigot to locate into the bore.

Back for some more marking out of the valve positions and the first was clocked true.
Then drilled, reamed, valve cavity opened up by boring and the same boring bar used to cut the seat before repeating for the second hole.
With the head clamped to the mill table the two spigots were brought down to size with the boring head.
I then clamped it in the vice and started work on the inlet & exhaust connections. The inlet worked out fine but if placed as dimensioned the 3/8pipe thread would have come out the side of the casting as shown you the bit of rod.
In the end I opted to move the threaded hole away from the edge but keep the 3/8" passage as drawing so it joined with the valve cavity as intended.
The whole cylinder/base asembly has now got quite large which meant it was difficult to locate centre and plot the six cylinder head bolt positions so I drilled the head and used that to spot the hole positions onto the end of the cylinder. In this picture the mill head is up as far as it will go and I had to make a bush to hold a stub length tapping drill in a morse taper collet as there was not room for any type of chuck.
And finally here it is in place held by some temporary fixings, still needs a good fettle around the edge and I'll also describe the rocker pivot later.