pcnewman

I purchased a Redcat Racing Caldera 3.0 with an SH .18 engine. It has a blue cooling head and a slide carb. Can you tell me if this motor is ABC or ABN contstruction? If it is ABN is there an ABC piston and sleeve available for it? I've kept a close eye on it through break in and each run not to get over 220*. I've only run one gallon of fuel (18% oil 20% nitro)through it and there is no pinch left at TDC. I can get it started when cold but once it warms up it will only run at or above about 1/4 throttle. I'm thinking a new piston and liner would solve my problem but I don't want to do it if ABN is the only choice I have.
Thanks for any help.