Military + Jet A + Small 2-stroke = Drones?

I'm surprised this conversion is not more common with Fox, since fabbing a head button would be so much easier than an entire head assy.

I've posted this before, but in my case I went the other way on my first Eagle IV 60. It had run on the test stand without issues as I at least started the break-in and tune, but three dead sticks with fried plugs in a row on the maiden flights finally clued me in there may be some deeper issue.

That was proven once the head was removed as the aft third of the piston had burnt away to below the ring. It had not eroded through the skirt yet, the reason there was no obvious loss of compression.

Since my own error by running 15%, was pleasantly surprised by no warranty pushback when sent in for repair. I assume since they had already come up with a modded head button to allow for higher nitro they may have seen a lot more of the same across their bench.

In the interim between my test stand runs and maiden I had acquired another identical 60 NIB and thought it would at least provide a basis for some home testing. I fabbed up 3 buttons with different chamber shapes and lowered compression and recorded my runs to see which performed the best.

NOTE: Would have to search my much earlier posting since a Windows update wiped out all my media and no amount of rebuilding will find the original pics of the 3 buttons to post again here.

Meanwhile, Fox advised me my engine had been repaired and test run with the updated button at no cost. I had requested an extra for that second engine and when arrived it was virtually identical to my own best performing. I have been running it ever since, (sold the first 60 and have that second NIB, along with the 74 and the other 2 buttons, set aside in my engine cabinet).

ps. Dave, you look to have quite a lot more experience with this than anyone else can ask: Did you find the diesel run hotter or cooler? One thing I learned when in AME school, and later flying helis powered by the Allison, (now R/R) and other turbines, was Avgas had less energy density than Jet A, but, oddly enough, burned much hotter.

pps. During winter ops, (that could get down to -55F) we switched to Jet B, which contained 1/3 Avgas, the only way to light off in those cold temps. At that mix there was no flight manual restriction on how long we could run with it.