It would be interesting to see a price quote from Cat Tail. In reality, I don't think there's much demand or interest as far as sales goes. Probably have a hard time selling 5 of the blocks in 5 years. I mean, who needs one? If someone has a block, they likely have a complete engine. Other than it's the major missing piece in the pile of most other easily obtainable and low cost parts. The one other piece I don't see readily listed on the spare parts web pages is Crank Shafts. Very few folks using these engines on a daily basis for 'work' I'd speculate.

Very nice effort Sirloin! A horizontal mill would come in handy, but I get that many don't have them. I suppose nuts could be installed on the cylinder studs inside the case for added strength. If there's room? This doesn't seem so difficult of a project, but then again they never do until you're into it. I build some things using the 'engineering on the fly' approach, and usually don't get bit to bad most times. Going slow, and planning each next move helps. This seems like a fun project, it would be a unique conversation piece for sure. 

sNOman, may I call you Nellie? You're such a NEGATIVE Nellie. I'm really cornfused as to why it would concern you if the idea is sound. Has anyone twisted your arm and demanded payment from you?
By guess and by gosh, anyone attempting this exercise with any care above that which the Indians have given the subject, should by rights succeed by (at least) leaps and bounds over their careless designs.   

John
There's a laser shop in Lockport I use from time to time. They are very reasonable and do good work. If you ever developed a set of drawings, I'd have them price the job. They can cut up to 1/2" steel I believe.

And a Snowman stopped by with a bit of heat to warm the winter a tad. Festive.

I'm very curious what you've been powering with your engine, that you've accumulated the thousands of hours on it necessitating
'a few' rebuilds?  Please use at least 5/16" or better yet, 3/8" plate steel, and let me know when the kits are available, and I will place an order. I have the welding equipment and Horizontal Boring Mill required to complete the work.

Interesting. I have a few questions. How long time wise did it take to make the 1 liter of oil?
Also, how is the 'reactor' powered, and how much fuel was consumed making the liter of oil?
And how much energy and time would be spent converting your woods into pellets?
Not to mention the cost of the pelletizer, unless you have one already?

My 722 is 22hp at 3600 RPM. Could very well be 12hp at 1800 as well.