gadget,
Sure, you can insulate the head.
Like this guy...
https://www.youtube.com/watch?v=V2ehdeEJOok
You can also run it slower and add a thermostat to keep the combustion temperatures high.
You can also load the engine up to 85% of the HP it creates at that lower speed, ensuring that it's adequately loaded and making as much heat as possible.
Good luck with the project, and be sure to post pictures/videos
veggie
Wow, that video was just uploaded 2 days ago, talk about timing. Glad to see someone else using insulation, hope to here back how it works. I'm thinking some rockwool with a nice sheet metal cover, it does look pretty hideous like that.
If anyone gets a chance to read the PDFs Hwew posted I recommend it. Lots of good info in there. One thing mentioned is a very lightly loaded diesel could see as high as 500 to 1 air to fuel ratio. This is a big contributor to the stacking or coaking issues. Think about this, lowering the engine RPMs down to match a light load may actually be better in some circumstances vs running at full RPM with a light load. Veggie mentioned it and I agree, matching load to RPM is something to consider. But what about bearing "lugging"? I think in a diesel it would smoke profusely before and "lugging". Anyone have any thoughts on this?

I don't think it would be a problem but thought I would ask anyway.
My motor is still disassembled in boxes at the moment. I started a new business and I don't have much free time. Right now, I'm building a new (larger) freeze dryer for the business and I don't know when I can get back to the motor. I will post pics/results once it gets going. Plus, its about 30F in my garage right now
If I do go the low RPM route, I would do a once a week full RPM / full load exercise combined with some water injection. The higher air volumes can do wonders to push out soot. We had a Mercedes diesel get stuck in full fuel once in a shop and it ran full RPM for about a minute. It left a pile of soot on the shop floor where the exhaust pointed down. The customer reported back no problems with the motor and that it ran better then it had for years. I'm not recommending anyone try this...lol