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Interesting. I suppose this wouldn't work so well if you were driving a car through a gearbox, your speed could be high with the throttle closed (e.g. going downhill in gear) and the mixture would then become excessively rich. But of course many model carbs would do no better.

Petrol fuel injected? Do you have a thread on this one somewhere? I'm curious how you decided to do the fuel metering for that, I know there are many possible ways and have sometimes idly thought about how I might do it. If I recall what I read correctly, the WW2 German engines with direct...

Engine cylinder or injection pump cylinder? I think it is quite difficult to do the injection pump one, as it is only 3.5mm in diameter and the surface smooth enough to be shiny if the photo is at an angle. I cannot see the surface finish with my eyes, let alone a camera. Perhaps with some...

That sounds like fun! I'll have to reach out once we get settled. We are planning to move in September, though it remains to be seen whether this is possible given various bureaucratic delays that are inevitable with such things.

Another idea would be to leave the injector in place as a seal and fit a carb to feed model diesel fuel straight to the intake, so still compression ignition but not a true diesel. I'll have one more go at the pump first however.

That would be the concern. It's probably worth one more try at making a workable pump plunger (at least I have a good test protocol so I don't waste my time now). Otherwise it might be time for a different cylinder head.

Munich. The 'dumb' method would be to make an extra chamber that bolts in place of the injector and contains the spark plug, and use a very thick head gasket to reduce the compression ratio. The gas flow to the plug would be awful but maybe that's ok for just getting it running?

A brief update. Ive got my head gasket issues sorted well enough. Remilling the head didn't allow the copper gasket to work, I think I simply used up all the available compression of the copper (it measures thinner now). A composite gasket with fire ring was made as planned and is working so far...

That's significant even for somewhat bigger engines. When my partner and I bought our sailing boat it came with a Mercury 3.3 HP outboard, about 80cc if I recall correctly. It compression tested way too low, but you could see the cylinder was in good condition. When I used a tester with a check...

On the topic of enclosed steam engines, if you have a single acting design is there any reason not to build it like a petrol engine but connect the crankcase to the condenser so any steam that slips past the rings gets sucked out? I guess one would need an oil separator so oil mist from the...

If you want to burn wood for power you can also use a wood gas generator and feed the resulting gas to a regular spark ignition engine. Not quite sure how the numbers work out on that vs a steam engine.

A dynamometer would be the best way.

The fumes from burning off epoxy are awful, and even worse they get into all the sand and make it stink forever after. It breaks down easily at aluminium temperatures, my epoxy cores basically just wash out. I started using a local brand of epoxy that is made from glycerol rather than...

I think they would work. And of course you can have whatever spring constant you like by stacking them. However I suspect many of us know how to wind coil springs on the lathe, so making custom ones is fairly straightforward vs buying bellville washers.

The 'bee's knees' would be a proper rigid hone, like they use on full sized engines and hydraulic cylinders. They can even improve the roundness and straightness of the bore, something the spring loaded ones have no hope of doing. Don't know where you'd start as far as getting one in the right...

Xylene is a rather good octane rating improver, so for spark ignition engines running on kerosene adding it would make knock avoidance that little bit easier.

The stones pivot so they should follow the hole. Not that I'd trust them to do that if I was actually trying to finish the bore to size! But with the hone you are just trying to remove the tool marks from boring and get a crosshatched finish, so as long as you just do that it should be ok.

I use a similar hone, only two stones though. I just run it in a hand drill, prefer to keep the abrasive grit away from the lathe.

Another 'relative' of the diesel to look at is the Hesselman engine. Has a low compression ratio (7:1 or so) and spark ignition, runs on oil. Fuel is injected a bit before the end of the compression stroke, and ignited by the spark timed to fire as the fuel cloud from the injector passes by.

Those swirl flaps often appear on diesels too, if they are 4 valve types.