Conversion of 4 Cycle Utility Engine to Steam

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vtsteam:
Instead of filling in the intake manifold space with lead, I decided to use pot metal (die-cast) -- zinc based alloy from some old auto door handles. It has a little higher melting point than lead, though well below that of the aluminum engine block. It is considerably harder than lead, and it was quite a bit more difficult to file back after the pour. I'd have have poured short, if I'd been a bit smarter about it.

The intake carb seat was simply blocked with wood, and I used a candle sooted piece of 5/16" drill rod (silver steel) to act as a core for the intake valve. In fact I had decided to use this same material as the bash valve lifter, instead of adding a pin to the top of the steam inlet valve.

The valve guide in the engine kept the drill rod at the proper 5 degree inclination toward the cylinder center.

vtsteam:
I originally intended to follow suggestions to weld a standard cast pipe tee to the head as a valve body and use a stainless ball and spring for the valve. A hole in the head itself would work as the valve seat after tapping lightly on the ball to form the seat. But later decided to use a threaded connection to the head -- which would allow some adjustment of the valve assembly height, among other advantages. It would also have been tricky to weld and center the fitting at the 5 degree angle required. Not impossible, of course.

Instead, I turned a separate valve seat out of brass for a press fit (later to be soldered) into a red brass pipe nipple. I used a pipe cap on the end, and silver brazed an inlet connection nipple threaded end into a close fitting hole in the valve body. A spacer at the top of the valve and the pipe cap would allow some adjustment of spring pressure. The valve was therefore a separate assembly that could be threaded into the cylinder head.

vtsteam:
A pattern was made of the head with bolt hole locations by placing a piece of paper over the engine cylinder and tapping it very lightly with a brass hammer -- similar to the old trick for cutting out a paper gasket. This marked the important location details on the paper -- one advantage of a sligthly dirty block -- an automatic grease pencil!

I also punched holes at the head bolt locations with a round pencil -- the tapered point was larger than the hole so it gave a nice locking paper rivet to keep the rest of the paper from moving while I did the rest. A piece of drill rod was also used to locate the center of the 5 degree inclined valve passage.

I now had a pattern for marking out the drill locations for the head bolts and valve.

I marked and cut out the second piece of steel sheet of the head. Most of the steel I used was scrap material.

vtsteam:
I decided to use braze instead of welding for much of this project -- I do own a welder, but need to get more proficient with brazing. It does use a lot of gas however, so I decided this time to try pre-heating the parts. I have a wood stove running this time of year, so why not put the pieces in the coals for a preheat?

I first pinned the two plates together with a couple of 1/8" steel dowel pins. Then popped them into the stove for a bake. The coals away from the vent kept the metal from oxidizing, and when it looked somewhat red, I pulled it out with tongs into a bucket of wood ashes, and trotted down to my brazing site (outdoors, cold) and brazed the part. The ashes definitely retained the heat, and braze was flowing shortly after lighting the torch.

vtsteam:
After brazing the parts together, I used my paper pattern to locate the valve hole, and set the drill press up to drill at 5 degrees. The drill rod and new head lined up perfectly when in position. The head bolt holes matched up.

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