Just took the head off and measured 18.42mm, so I guess It's one of the 0.28 c.i. varieties from 1QwkSport's list of choices (if my Harbor Freight caliper is to be trusted).. I would guess it's the 1s model, as the 0.28 2S seems to have the Axial logo printed on the side of its motor casting as where mine does not. The head on that one also looks to have 4 divots machined in the cooling fins where mine only has 2. It doesn't appear to be the 0.28RR comp engine since that one seems to come only with a black head.
Used nitro trucks are a gamble. [/QUOTE]
[QUOTE]
That;s certainly true, but fortunately I've gotten pretty lucky with buying used engines over the years. Most were so gunked up from sitting you couldn't even turn the flywheel with ChannelLocks.
Thanks again for the help.