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Don't give up on your metal rings, they'll bed in and improve greatly if the engine is able to run.

Almost all diesel injectors are hydraulically actuated. The detroit ones just locate the pump on top of the injector, rather than having a pipe connecting the two.

It's worth noting that modern automotive diesels are partly operating on the second cycle. Premixed combustion is preferred because it produces less pollution, but longer mixing times produce a more violent initial combustion so a trade-off has to be made. That's also why compression ratios of...

Ideally the tangential speed of the gas should be zero at the exhaust, it should be flowing entirely radially or axially depending on the turbine layout. Take a look at a turbocharger turbine and you'll note that the blades are angled away from the direction of rotation at the exhaust- that's...

The behaviour of any turbomachine has a lot to do with the pressure ratio across it. Tesla turbines are impulse turbines, in that the pressure drop occurs entirely in the nozzle and the resulting jet of high speed gas then transfers its momentum to the turbine wheel. The velocity of the jet...

propane has a wonderfully high octane rating, it's not unheard of to inject it into the manifold of diesels as an auxiliary fuel, in which case it doesn't ignite until the diesel is injected and its ignition sets off the propane. What was probably happening in your trimmer was that some deposits...

After some trials, tribulations and a redesign, here are the rockers fitted along with the pushrods. I like this system of rocker pedestals and trunnions, it turned out very nicely and I'd certainly use it again. I would however beef up the middle of the rocker a bit, I managed to squash one in...

What component is this?

Low surface area to volume ratio is definitely an issue. Heat loss rates are higher relative to the total amount of air. Likely more an issue for cold starts than once the engine gets going.

The downside to spiral taps is that in my experience they are easier to break than a standard tap (also they don't seem to work so well in small sizes). Spiral point is good for through holes but awful for blind holes. And of course fluteless is useless for brittle materials and plastics. Horses...

Anyone who single point cuts a thread when they could have used a tap or die has waaaaay too much time on their hands. I say this as someone who has single point cut a lot of threads. What's even better is when you can cold form the thread with a fluteless tap. No stopping to clear chips, just...

I don't often have time to do machine work during the week, but the 3d printer is at my apartment so I can sometimes print a part. I just did the rear gear cover, from carbon fiber filled nylon 6. I think this is the best part I've ever printed from this material, must have finally got the...

This resonance for performance business is very common on modern cars, in fact it isn't uncommon to find cars with manifolds that have multiple runners of different lengths and shutters that can open and close them, so that the engine can have two or more optimal resonant speeds. The automatic...

I have a small engine compression tester, but I would need to make some kind of funky adaptor to allow it to connect up to the injector hole. I think my next mission is the rockers and pushrods. I've been a bit indecisive on this matter, and actually designed two options Which option do...

A bit more progress on the cylinder head. Valve springs, keepers, hold downs for the injector all made. I lapped the valves and made a crush washer for the injector. With the head on and some grease as a temporary seal to the block, I was able to test for compression. The good news: there is...

Nylon can be a little peculiar because it absorbs a lot of moisture from the air (and becomes a lot softer when it does so). I've worked with nylon bars that have a substantial difference in colour at the surface where the plastic has been exposed to the atmosphere, compared to the interior. I...

The emulsion tubes have another important function, which is to compensate for the tendency for the mixture to get richer as speed of airflow through the carb climbs. Usually they are fed by a jet or needle such that the level of fuel in the tube drops with increasing flow through the venturi...

I for one am looking forward to seeing what the results are like!

My thinking on the plenum/trumpets layout is that the trumpets could act as standpipes that stop the 'pooling' from entering the cylinders at all. Though perhaps this might lead to problems with the mixture ratio when the throttle is suddenly opened or closed.

Some early radial engines brute forced the problem by ducting the mixture through a rotating fan mounted on the rear of the crankshaft, the spinning blades 'stirred' the mixture in an attempt to even out the fuel flow to each cylinder. Later that role was assumed by the gear driven supercharger...