Conversion of 4 Cycle Utility Engine to Steam

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vtsteam:
Reamed the valve space to .001" oversize and checked the fit with a piece of 1/2" drill rod.

Then I drilled .375" upper valve orifices, and then faced down to an eighth above that at 9/16" diameter with an end mill.

Then I blind tapped the holes for 3/8" NPT pipe. The valve body is properly centered under the inlet and outlet bores. Everything looks good.

Next step is make the valve.

vtsteam:
After many days of thinking about and drawing out valve diagrams, I have come to realize that I can't do what I want with a rocking valve. The only possibility at this stage, using the head I built is to go with a full rotary valve. And after much consideration of the way to drive that, I've also had to discard the idea of an eccentric, because I'd need at least two eccentrics and connecting rods to make a full rotary valve work.

The only way to achieve what I want is either add a timing belt or chain drive. I've settled on a timing belt because of the reduced need for lubrication of valve gear. Not my original preference. I really looked forward to making the eccentric gear. It would certainly look better running. But I do want this to be a practical engine, and the focus of this project was to produce a steam conversion with efficient valve timing -- in fact to be able to experiment with efficient valve timing.

So, I've ordered some timing pulleys -- I may yet make my own after they arrive -- once I have them I can easily copy the tooth profile onto a cutter for that size pulley.

I'll wait on ordering the belt to see what the true distance is after adding the pulleys and a head gasket and bolting the head down.

I'm still working on the actual valve rod configuration, as all my original work is now wrong. Still, I've learned a great deal about valve mechanism and timing -- I think I understand some important underlying principles of valve drives in general now, and shouldn't have trouble designing them in the future.

Here's the engine as it stands now, awaiting delivery of the timing pulleys. And a picture of it back when it was a seized block.

DavidF:
I got to thinking, couldn't you just mill slots thru the valve for the ports? Kinda like cutting a keyway groove except that it goes all the way thru the shaft and have two slots so many degrees apart. One for admission and one for exhaust. That's provided you didn't drill all the way thru the head yet because you would have to slot those passages as well...

vtsteam:
David, do you mean in a rotary or oscillating valve?

Slots in a rotary valve will give you two openings per revolution.

DavidF:
Occilating. So you can drive it from an eccentric.

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