There are a lot of one-off home made engines like that around, I would bet that is one of them..I have seen a v-12 RollsRoyce Merlin engine that was 8 inches long too..the smallest I have seen was a .005 engine half the size of a cox .010 production engine..it was home made too, I have also seen several cox cylinders used on 3 or 5 radial engines and ,,there is a small V-8 that is produced , but its ~$3500...and it has an optional supercharger....Rog